Final Report Summary - BIFFIO (Cooperation between the aquaculture and agriculture sectors with the intent to use animal manure and fish faeces for sustainable production and utilization of renewable energy and recovered nutrients)
Executive Summary:
BIFFIO is a project within Research for the Benefit of SMEs in which the research work is funded by the European Union’s FP7 administered by the Research Executive Directorate (REA). The project was officially started on November 2013 and has a duration of 39 months. BiFFiO is an example of industrial symbiosis, initiated from aquaculture, agriculture and renewable energy industries for a sustainable waste management by producing renewable energy from mixed aquaculture and agriculture waste, in addition to production of fertilizer. The consortium consists of eight SMEs/AGs, and three RTD performers.
The project addresses the challenge which aquaculture and agriculture industries face in respect to regulatory and societal requirements for the waste produced, an issue which is in need of sustainable solutions. A great majority of aquaculture farms are located in remote areas, close to agriculture activity where large scale biogas plants are not a good fit based on the amount of waste produced and high cost of long-distance transport. This limitation has emphasized the need for the cross-sector approach chosen in for this project, where local livestock and fish farms can combine their waste and collectively take advantage of the end- products in a plant scaled to meet the demands for their specific waste needs.
Thus, the main objectives of BiFFiO are 1) Development of a new best practice and novel technology for handling mixed waste from aquaculture and agriculture for production of energy, and use of the digested waste, 2) Development from current large scale SOA technologies for treating animal waste, to an economical, efficient and scalable three-stage system of pre-treatment, biogas reactor and fertilizer recuperation; 3) Application of new technology in the agriculture industry alone or together with fish farming industry, 4) Impact on socio-economic conditions through the benefits of improved hygienic and environmental. standards of closed fish farming and by reduced greenhouse gas emissions and other pollution burdens from the agriculture sector.
Project Context and Objectives:
The concept of the BiFFiO project is to mix the waste readily available from fish farms and manure waste from the agriculture industry in a reactor for production of biogas, which in turn can be used to fill the need for renewable energy in the aquaculture industry and supply fertilizer products to the agriculture industry.
A great majority of aquaculture farms are located in remote areas, close to agriculture activity where larger-scale AD plant solutions is not a good fit based on amount of waste produced and distance of
transport of waste. This fact limitation emphasizes the need for the cross-sector approach chosen in for this project, where local livestock and fish farms can combine their waste and collectively take
advantage of the end products in a plant scaled to meet the demands for their specific waste needs.
Using fish waste together with manure from animal production will boost the biogas production versus using manure or fish waste alone, providing a benefit to both industrial sectors. The BiFFiO project partners, representing the aquaculture, agriculture and renewable energy industries, hence see a great opportunity in production of renewable energy from mixed aquaculture and agriculture waste. The partners will develop energy efficient, cost effective, easy to implement and easy to operate biogas reactor technology. The reactor will be based on high-rate anaerobic digestion (AD) and will be designed for recovery of valuable biogas and nutrients from the digested waste, thus reducing pollution and emissions.
There is a need for sustainable solutions to handle the waste which is produced as part of the daily
production in both the aquaculture and agriculture sectors. This project will contribute to providing sustainable solutions by converting waste into renewable energy and valuable end products that will benefit the European aquaculture and agriculture industries.
This new biogas technology will facilitate a new best practice for handling combined waste from aquaculture and agriculture by:
• stabilizing the organic matter
• reducing odours and pathogens
• controlling physical and chemical contaminants
• providing recyclable end products in the form of biogas and digestate
As the aquaculture industry is moving towards increased use of recirculation aquaculture systems
(RAS)1 and is exploring the use of closed fish cages at sea, the industry needs new technology for
sustainable handling and utilization of the fish faeces and waste. Presently, fish farms have to store the sludge for further treatment2 this creates challenges such as odour issues and handling costs. Production of 1kg biomass (fish) generates approximately 180g of fish faeces3, 4. Based on annual fish production in Europe, there is a total production of approximately 454.172 t fish faeces in Europe per year (FAO). In traditional flow-through fish farming facilities the production of waste products could cause environmental problems like excessive oxygen depletion and increased algal growth. Especially in sheltered or closed coastal areas and waterways the action of coastal currents can be insufficient to dissipate the wastes. Therefore, in order to increase overall production, while minimising the impact on the environment and complying with environmental regulations, land-based RAS systems and closed-cage fish farms are emergingHowever, the collection of fish faeces and waste represents a cost for the fish farms in form of handling and transport. Further, although RAS systems reduce the negative impact on the water environment by collecting waste, they consume more energy to support water circulation to the stock than the technology they replace. A potential solution is the development of new technology that can utilize the fish farm waste to generate the energy required, thus reducing the carbon footprint of the aquaculture industry. Likewise, as agricultural industry is intensified and the price of inorganic fertilizer continues to rise, livestock farms will need new sustainable methods for handling the excess manure and redistributing the organic manure fertilizers. The livestock sector is also a high contributor to greenhouse gas (GHG) emissions, which highlights the need for improved, more sustainable approaches to livestock production. High livestock density is accompanied by production of surplus animal manure. This represents a significant, localized pollution threat. Excessive fertilization of arable land can damage the environment and is not economical since valuable nutrients used in excess are
generally washed into waterways. Intensive animal production will benefit from suitable manure
management facilitating export and redistribution of excess nutrients from manure and optimize
nutrient recycling.
The EU has fixed a goal of supplying 20% of the European energy demands from renewable energy
systems (RES) by the year 2020. A major part of this renewable energy will originate from European farming and forestry. At least 25% of all bioenergy in the future is likely to originate from biogas, produced from wet organic materials such as: animal manure, whole crop silages, wet food and feed wastes, etc. Therefore, there is a pressing need to develop economical technologies that enable production of renewable energy for smaller fish and animal farms in rural areas.
The BiFFiO project will enable SMEs from the aquaculture, agriculture and energy sectors to
increase the sustainability of their production, and by finding economic viable solutions for
handling waste products, will help increase their competitiveness. The initiators of this
project: the Scottish Salmon Producer Organisation (SSPO) and the British Trout Association
(BTA), representing SMEs in the fish farming industry, have recognized the urgent need for
collaboration and further R&D to find economic and functional solutions for sustainable use of fish wastes. Landberatung GmbH (Landberatung), the European Biomass Association (Aebiom) and Norsk Bioenergiforening (Nobio), representing the agricultural and bioenergy SMEs, see the wealth of opportunities for improved utilization of waste products by combining the waste sources from fish and animal farming. Included in the consortium are OTHER-SME partners that can produce, deliver and distribute the BiFFiO technology to the market post-project, namely: Awite Bioenergie GmbH (Awite), OÜ Kalavesk ltd and Aqua & Waste International GmbH (a&w) delivering turn-key technologies for water, wastewater,
environmental and renewable energies. As it is difficult for the associations representing the SMEs, and the actual farms themselves, to finance and run R&D activities, the EU scheme for Research for the benefit of SMEAssociations is a suitable platform, enabling outsourcing of the RTD activities essential in the BiFFiO-project. Thus, the initiators have engaged Aqua Consult Ingenieur GmbH (ACI), University of Liverpool (UoL) and Teknologisk Institutt as (TI) to perform the RTD tasks in the project.
The European aquaculture industry employs approximately 80,000 people, equivalent to 3.3 per
10,000 of the active population5, but is dominated by SMEs. The agricultural sector, which provides
approximately 6.6% of the total employment in the EU region6, is likewise dominated by SMEs. Thus,
these two industries represent very large groups of SMEs with great importance to Europe. The
majority of the SMEs in these industries are located in remote areas where large-scale AD plant
solutions are not a good fit based on amount of waste produced and distance of transport of waste.
This limitation emphasizes the need for the cross-sector approach chosen for this project, where local livestock and fish farms can combine their waste and collectively take advantage of the end products in a plant scaled to meet the demands for their specific waste needs.
The idea of the proposed project is to use a high rate biogas reactor to treat the waste. High rate biogas reactors are available in various designs, e.g. the up-flow anaerobic sludge bed reactor (UASB). With very few moving parts, apart from circulation pumps, anaerobic bio-processing is robust, provides scalability down to small units, and poses low energy and maintenance costs. The sludge production is about 1/10th of aerobic treatment. Diatomaceous silicate and bauxite aluminates have proved very efficient absorbents for the water-soluble inorganic phosphorous accumulating in the water-phase following a biogas treatment. A second treatment stage will harvest Phosphorus (P) and ammonium-Nitrogen (N) in a bioavailable form to support plant growth.
Following hygienisation, the biogas sludge and absorbent sludge will be usable and saleable products for soil amendment. The solution for handling the waste stream will be cost-effective, functional, sustainable, and facilitate production of useful end-products for use in the agriculture sector. The digested waste will be made suitable for storage and used as fertilizer. Analyses show that fish faeces have relatively high bio-methane potential and a particularly high content of phosphorous compounds7 and, therefore, represents a potential source for biogas production as well as a valuable source of nutrients for fertilizers or for other uses. Life cycle assessment demonstrate that the most energy efficient and climate friendly approach is to recuperate energy from the waste by biogas production and harvest the nutrients (N, P, K) from the combined waste. Using fish waste together with manure from animal production will boost the biogas production versus using manure or fish waste alone, providing a benefit to both industrial sectors. Case studies demonstrate that, even in a very high energy efficient recirculation farm, the biogas potential of the fish faeces produced “on site” represents a maximum of 8-10% of their total energy requirement7. Anaerobic digestion of animal manure and slurries offers several benefits by refining and enriching their fertilizer qualities, greatly reducing GHG emissions, reducing odours and pathogens and producing renewable fuel like biogas. Although advanced biogas reactors are in use in Europe, the existing technology is neither developed nor scaled to handle the waste from fish farms in an economic, robust and user-friendly way. Thus, is a need for further innovation of biogas production solutions for use in fish farming and agriculture in remote areas... The fish farming activity is often located in more rural areas as are the agriculture sector. In order to have a higher amount of energy coming from biogas at fish farms, cooperation with a second supplier of a waste source for biogas production is called for. Cooperation between the aquaculture and agriculture sector is especially interesting since the agriculture sector has readily available sources such as manure for biogas production. Further, a regional cooperation between the aquaculture and agriculture sectors ensures short transport distances.
Main Project Objectives:
1) Development of a new best practice and novel technology for handling mixed waste from
aquaculture and agriculture for production of energy, and further use of the digested waste.
2) Development from current large scale state-of-the art (SoA) technologies for treating animal waste, to an economical, efficient and scalable three-stage system of pre-treatment, biogas reactor and fertilizer recuperation, which can be located at or in the vicinity of most near shore and on-shore closed fish farm operations.
3) Application of new technology in the agriculture industry alone or together with fish farming
industry, on both remote and central locations to save costs for waste transport and deposition.
4) Impact on socio-economic conditions through the benefits of improved hygienic and environmental standards of closed fish farming and by reduced GHG emissions and other pollution burdens from the agriculture sector.
Operational goals:
To greatly increase biogas yield from combined waste, major reduction of reactor volumes by highrate technology, lower investment costs per volume of biogas produced, elimination of hygienic hazards, optional full coverage of fish farm energy needs in terms of electricity and heat from combined fish and other waste, and add value to both industries by return of fertilizer and soil
remediation products of cropland quality.
Project Results:
1. DESIGN CRITERIA:
For waste composition analysis, samples were taken from two representative cattle farms: Wood Park is a medium sized dairy, high intensity farm where most of the cattle are housed indoors. Ness Heath is a small beef farm with a small herd of pedigree Herefords kept mainly outdoors on pasture. These represent extremes of a scale. Laboratory analyses were carried out to define and characterise the physical (moisture content, particle size, degradability), chemical, and biological characteristics (including biodegradability, nutrient content and the presence of potential contaminants). Determinands were: Total Solids, Particle size, n-Caproic acid, Acetic acid, Propionic acid, Iso-Butyric acid, N-Butyric acid, Iso-Valeric acid, N-Valeric acid, Iso-Caproic acid, Acetic acid, total Nitrogen, Ammonium Nitrogen, C.O.D. (fresh), Volatile Solids and pH. The samples were assessed in-house for copper, iron, arsenic and lead, however, all levels, as expected in agricultural manure, were lower than our routine analysis (safe levels) could determine: 1mg/l Cu, 0.05 mg/l Fe, 0.2µg/l arsenic, 20mg/l Pb.
Fish farm waste was sampled from four aquaculture facilities: two Salmon hatcheries in Scotland and two trout farms in England. Marine Harvest Lochailort is a large, modern facility with a yield of 15 to 16 million fish. >60 tonnes of waste is collected per week and spread on local farms. Tullich is smaller - 10-12 tonnes of solid waste is generated each year and spread on local fields. Chirk only stocks rainbow trout. Waste is pumped into settling ponds and left to dry and eventually used as manure for local fields. Kilnsey Trout Farm is a fly fishery and trout farm. Waste sediments sink to the bottom of the tanks and the clean water flows out. This is then spread onto fields within the park estate. The Total Solids varied between 0.22% and 18.7% in fish farm waste and 4% and 19.2% in cattle waste (Marine Harvest pre- dewatering and filtering is 2% solids, rising to 19% solids post- filtration). For the cattle farms, raw waste from Wood Park farm from the slurry lagoon had a total TS content of 4%. We estimate the C:N ratio of our fish waste to range from 9:1 – 11:1 in Marine Harvest samples, to 12:1 – 16:1 in the Kilnsey samples. In the cattle manure, the C:N ratio varies from 2:1 in Ness Heath to around 20:1 in the Wood Park. This is likely to vary over the year, with forage type, and undigested feed components (such as grains). pH varies in these manure samples – generally lower in the aquaculture samples (pH 5 to pH 6.9) and higher in the cattle samples (approximately pH 7 in the Wood Park Main samples). Anaerobic digestion is favoured within parameters pH 7 to pH 8.5 therefore, it may be necessary to buffer the pH of the feedstock.
The samples of slurry from the dairy and beef farms and from the fish farms were analysed and results presented in the D1.1 report and discussed with partners at RTD and Management meetings. We drew the following conclusion. The slurries and manure examined fall within normal/expected parameters. The range of TS values cover a sufficiently wide range, both within individual farms and across farms, to provide great scope for “designing” feedstock compatible with a wide range of AD technologies. The pH ranges measured are lower than ideal, therefore pretreatment or intreatment buffering to raise the pH. The consensus was that Continuously Stirred Reactors with buffering and a facility for daily renewal of feedstock was a simple design that offered flexibility and a high likelihood of success in using these slurries as feedstock. Volatile Solids and C:N ratio data suggest that the manures and slurries examined have good biogas potential.
The safety issues regarding biogas have also been investigated. For this, the process complexity, the usage of biogas and possible explosion zones on biogas plants has been examined.
In order to map the main hazards related to the usage of the end product, the legal definitions have been researched and the main hazards related to the usage of the digestate as fertilizer and for animal bedding have been investigated.
After this the related legal and safety issues regarding the usage of the end product are described and aspects regarding the localisation of a biogas plant are discussed. Finally a risk assessment for a biogas plan was done.
Regional benefits and restrictions:
A general research regarding EU-regulations,-directives and -decisions has been conducted. In addition to this TI, UoL and ACI did a research at their home countries regarding the implementation of the found EU regulations and further national laws related to biogas or waste from aqua- and agriculture.
Handling strategies:
In order to define handling strategies research has been conducted regarding possible factors (e.g. composition of the sludge, sulfate- and salt-concentration) influencing anaerobic digestion of waste streams from brackish/marine RAS. Furthermore possible reactor types have been investigated for the anaerobic digestion of aqua- and agriculture waste.
With the help of SME-AGs and their members, we were also able to map logistic challenges, define best solutions and identify criteria for biogas process design at actual fish farm and farm land sites in selected countries that SME-AGs have their members. The work consist of; 1) Literature and publication search for relevant information. 2) Questionnaire to be distributed to members of the SME-AGs. 3) Interview questions to be asked to selected end users, which are members of the SME-AGs.
The literature study and the survey show that there is a great potential for aquaculture farms to collaborate with their agricultural farms in neighborhoods and install one biogas plants in the vicinity of their farms. This can be economically efficient by looking into the energy and waste handling costs that these two sectors are nowadays dealing with.
In the studied agriculture farms , based on questionnaire and interviews, average results shows that 100-500 livestock units are kept and farms are using approximately 50 MWh/year which costs about 10 000 £/year. Farms are using electricity from the grids primarily and use diesel or oil as a secondary source of energy. A typical studied farm uses more that 50% of the energy for heating/cooling. They are collecting approximately 750 tons of manure per year and mostly use it as fertilizer on lands.
In the studied aquaculture farms, based on questionnaire and interviews, average sizes of the farms are between 1000-5000 m3 with around 1-5 million annual fish production. They use 100-500 MWh/year which cost around 100 000-500 000 £/year. Farms are using electricity from the grids primarily and use diesel or oil as a secondary source of energy. These farms are producing fish feces and uneaten food waste about 20-100 tons/year. This amount of waste has a cost burden for transport and waste handling of about 1000-5000 £/year. The interviewed company has analyzed the biogas potential of fish faeces and found it unprofitable. They claim that acceptable payback period for them is about 3-7 years. In addition, there is no governmental support for using their waste in biogas plants.
Interview was made with a biogas plants owner with CSTR reactors with the feed of waste silage and solid pig manure. The plant is handling 5475 tons per year and in return produces 130500 Cubic Meters of Biogas. They can accept cattle slurry of 9-11% dry matter but not interested to accept fish waste because they need to get permission. From literature study, input of 4418 tons per year (4380 tons of cattle manure which is co-digested by 37.5 tons of maize crushed grains), leads to electric energy gross production of 327 MWh per year.
2. PRETREATMENT TECHNOLOGY:
A vital component of feedstock pre-processing is to evaluate the current available SoA pre-treatment options and select the best method(s) for the waste characterized in WP1, and fulfill the required and preferred properties to be run in a high-rate anaerobic reactor in WP3 (UASB and CSTR) at mesophilic conditions. The selection of the pre-treatment methods is based on economic consideration – cost versus benefit, robustness, safety and practical issues, like user friendliness and functionality.
An overview of the benefits and disadvantages of each method was presented in the deliverable 2.1. Based on the evaluation study and input from partners, the pre-treatments with the highest potential for the most optimal final result is selected, considering cost benefit, potential increased biogas production, user friendliness, robustness and improvement of digested matter.
Regarding these criteria, different pre-treatment methods were evaluated and selected for further testing at the BiFFiO pilot plant. The evaluated methods were dewatering (stepwise filtration, screw press, decanter centrifuge and sedimentation), particle reduction (grinding, cutting and macerating), ultrasonic treatment, acid, alkaline and metal salt addition, enzymatic hydrolysis, thermal (conventional, microwave and steam explosion) and combined methods (FSPM and flocculation and sedimentation). Among these treatments the selected methods for further testing where:
• Sedimentation (for dewatering)
• Maceration and grinding (particle reduction)
• Thermal heating (for hygienisation)
• Mixing (to ensure consistency).
The selected treatments has the advantage to make the feed easier to handle for the system, but will also give additional advantage as increasing biogas yield, potentially reducing AD inhibitors, hygienisation and reduce energy demand.
Based on the evaluation and selection of appropriate pre-processing methods, the pilot unit was installed at the School of Veterinary Science University, University of Liverpool. The entire plant consists of two containers, where the pre-treatment process and laboratory occupies one of them. The three sedimentation tanks are integrated outside the containers. In the pre-treatment-container there are work benches where the equipment is installed. Duo to practical and economic reasons, small scale equipment and simple food processor machines were applied.
The available pre-treatment equipment at the BiFFiO pilot plant are:
• 1 pressure boiler for thermal treatment and hygienisation
• 1 small oven for drying preparation for total solid measurement
• 1 kitchen machine with a food processor for cutting/macerating
• 1 industrial mixer unit for blending
• 1 scale for weighing
• 1 meat grinder for grinding the fish cuttings
• 3 water tanks for sedimentation of saline fish sludge, freshwater fish and manure sludge
• A number of pipes to transport sludge, connecting the sedimentation tanks to the pumps
• 2 Pumps for loading and unloading
• 6 barrels for storage
The pre-treatment processes will operate using a batch system and the sludge would be transported between unit operations by pumps and manually in buckets by the operators. The pre-treatment methods where integrated at the pilot plant in Liverpool during November 2014 and finalized in December 2014.
In the pre-processing of animal slurry collected from the farms, the slurry is first stored in intermediate bulk containers (IBC). Waste in the IBC is stirred with paddle mixer according to the procedure described in Deliverable 2.1. Portion of the waste is first transferred to a clean , labeled bucket. Samples of 1,5L are decanted then decanted to a blender. After blending, coarse particles are removed by a 7 mm sieve. The blended and sieved samples are then transferred to a 120 keg where they are allowed to settle over night.
In order to feed the reactors with fish slurry, dry matter content for feeding the reactors is 6-7%. To obtain this dry matter content, first a 14% dry matter content is prepared and then diluted 1:2 to attain the final slurry of 6-7% dry matter. Fish cuttings are broken down with a blender in 1:1 ratio (50% fish, 50% water). After further blending for homogenization, the cuttings are passed through a sieve of mesh size 3-5 mm. The sieved fish slurry is then transferred to a collecting bucket.
For measurement of pH level, conductivity and dry matter 4 samples are taken and analysed on a daily basis. Measurement of pH and conductivity are done with a small volumes of samples that are the returned to the mix. For measurement of dry solids content, a well-mixed sample is evaporated in a weighed dish and dried to constant weight in an oven at 103 to 105°C. The procedure and calculation of the dry matter content is described in D2.1. pH is adjusted by adding hydrochloric acid to elevate the pH level, and sodium hydroxide to lower the level as required.
Main achievements: The pre-processing has been necessary work that should continue as long as the AD scenarios have to be run, and the required digestate for the growth trials has been obtained. A good amount of data from the pre-processing has been also obtained during the duration of the AD operation; procedures for preprocessing of animal slurry and fish waste as well as the mixes of these has been established; knowledge on the quality of the substrate that enables optimum operation of the reactors with different mixes has been aquired; optimum values of parameters for smooth operation of the anaerobic digestion and high quality digestate for the growth trials have been maintained in the course of the Biffio trials.
3. AD TECHNOLOGY:
Based on the input from WP1 and the state-of-the-art a design of the current high rate bioreactor system will be fit to the need in terms of capacity, efficiency and product quality of biogas and remains.
For development of the AD, the results from WP1 have been evaluated and according to the results 4 test scenarios/system setups have been created. Based on the results it was decided to use the CSTR-reactor technology for the main anaerobic digestion reactor. Afterwards a test container with 4 CSTR-reactors (80l each) has been designed.
As part of the AD system, the control of the reactor and especially for the AD process a control system consisting of liquid and gas measurements have been develop. Temperature, Conductivity, pH and redox-potential will directly be measured within the reactor. The produced biogas will be analysed for Methan (CH4), Oxygen, Hydrogen sulphide and Hydrogen. The feed and the output will be analysed for it composition by lab-analysis. A test container containing 4 CSTR-reactors, control system, Biogas measurements and other necessary instruments and aggregates has been build according to the outcome of the design work. The container was transported to Liverpool and has been connected to the pre-treatment system.
A test matrix for the trials has been defined where different loads and mixtures will be tested. In order to archive repeat determination of results all scenarios will be done twice with different reactors but the same conditions (loads and mixture). The matrix that was created in Reporting Period 1 expanded due to the addition of fish cuttings as substrate from the aquaculture sector.
Test the prototype reactor. All scenarios from the test matrix and the replications of them have been successfully completed. During the test scenarios a view operational problems have been solved. All plant analysis have been executed and the received data has been evaluated.
4. SEPARATION AND USE OF DIGESTED MATTER:
The preliminary task of digestate post-processing is separation of the liquid and solid fractions.To start with, the task work was carried out with review literature regarding available methods for liquid-solid separation of sludge, advantages and drawbacks of the identified separation methods and their applicability to the digestate generated by the BiffiO process. Further to this, the literature review addressed the need (advantages) of separating the solid fraction from the liquid in the digestate as well as the value chain of the separated fractions.
From the identified methods, a short list was prepared based on relevant features for the BiFFiO best practice. These features include: Retention of nutrients in the separated fractions, Easiness to operate and maintain, Capacity/rate of dewatering, Footprint/need space, Reliability, Energy consumption, Possibility of automation, Suitability to different types of sludge, Instalment cost, Need of operator attention, Need of polymer and Secondary pollution.
Based on these considerations the following methods were included in the short list of potentially applicable methods for liquid –solid separation in the BiFFiO best practice. However, special consideration has been made in relation to technical complexity (need of qualified operators), economic implication for the end users and willingness of the market to pay for the solutions, as there was consensus in the consortium that cost benefit value should be given high priority in selection of the methods that suit the BiFFiO best practice in posttreatment of digestate. As a result, the short list of the short list included screw pressing, belt pressing, pressure filter press, drying
Centrifuges, electro-chemical flocculation/coagulation. Of these, screw pressing and electrochemical flocculation were taken forward as the most convenient conventional and emerging technologies respectively for the BiFFiO best practice. The functionality tests of these two methods should be used for selecting the best practice of liquid-solid separation in BiFFiO best practice. Manufacturing of a screw press unit was beyond the capacity of TI or the other beneficiaries. Therefore, a number of suppliers across Europe, especially in Germany and the UK, were contacted for manufacturing or leasing of a test unit. The smallest test unit that can be manufactured has a capacity 200L/h, while the Biffio plant can generate only 8 l/d. It has not been possible either to get any centrifuge unit with such small capacity. Therefore, the functionality tests were undertaken with a bench size electrostatic flocculation unit built in cooperation with a Welsh company (Power and Water). The Laboratory scale unit was installed at the University of Liverpool and subjected to tests using sludge from the BiFFiO anaerobic digester.
The electroflocculation process consists of electrolytic addition of metal ions to polluted water at an anode, and generation of gas microbubbles at a cathode in electrolysis cell. For the process to take place, electrodes are placed in water with an electric potential applied across the electrodes in order to cause electric current between them. The process operates based on the principle that the cations produced electrolytically from iron or aluminum anodes are responsible for the growth in the aggregation of contaminants from an aqueous medium. For running the process the test system built consists of a power supply unknit, a reaction chamber with electrodes at opposite corners of the chamber, a buffer tank, a peristaltic pump for circulation of the digestate to be processed and ultrasound cell for enhancing the hygienic quality of the separated fractions. Analysis of the dry mater content in the liquid fraction has been done after separation of the fractions using both iron and aluminium electrodes and at 2 and 5 amps. In all the samples analysed, the dry matter content is under 2,2% down from 10 -15 % in the feed digestate. This considerably high compared to what can be obtained with SOA methods. The level of separation could be potentially increased significantly by elevating the amperage to 15 – 20 amperes, but the test unit is not designed to such high power.
In the task of nutrient recovery, three main mechanisms of nutrient recovery were evaluated: i) Static accumulation of nutrients by absorption/fixation in three types of readily available and cost-effective media: activated carbon, zeolite and vermiculite by absorption or fixation from the liquid fraction of the digestate ii) use of a circulation system with an inline filter/media housing and iii) use of a circulation with a laboratory-scale electroflocculation and ultrasonic cell. The latter two mimicking in-line post-treatment system systems. We performed laboratory tests to determine the level of removal/recuperation of nutrients P, K and N. In both the static and circulation tests with minerals/activate carbon, we found that zeolite sequestered the most ammonia while activated carbon had little or no net effect. While in our experimental setup Vermiculite had less of an effect, the mass of vermiculite was 0.2 to 0.25 that of zeolite, therefore we would speculate that a similar mass of vermiculite may yield far higher removal rates than the zeolite. Electroflocculation shows potential for producing a concentrated fertilizer with both Ammonia Nitrogen and Phosphorus substantially decreased in solution. In contrast, potassium sequestration was not achieved. Further, there was substantial removal of the metals copper and zinc from solution. All of these result were achieved without extensive optimisation of the device.
Activities of the task related to storage, handling and use of the solid fraction are based primarily on literature study, discussions with experts in the field of digestate management and site visits. The outcome of the investigation is summarised as follows.
Storage: Usually, digestate is produced throughout the year and as a result there is a need to store until the appropriate time for application as a fertiliser during the growing season. The length of storage period will depend on several variables, including geographical area, soil type, winter rainfall, crop rotation and national regulations governing digestate applications. In many cases 6-9 month storage capacity is recommended, especially in areas designed as nitrate vulnerable zones (NVZ), and in some countries it is obligatory (e.g. Sweden, Denmark, Italy, Germany Austria). Unlike whole slurry especially from dairy cows, digestate does not usually form a crust during storage because the solid material that would have formed the crust is broken down during digestion to produce the biogas. When digestate is stored in open tanks, ammonia and methane gases are given off. These emissions can be reduced if the surface of the liquid is covered by a protective layer. The regulatory requirements of the IPPC (Integrated Pollution Prevention and Control) Directive and some national voluntary requirements of Biofertiliser Certification require that digestate stores be covered, but this may not be the case for on-farm storage of the finished product.
Location of the storage will be at the preference of the operator; either at the AD plant, or separate from the plant at the point of land application (if land is secured for spreading). Storage containers will need to be constructed to meet Health and Safety Executive (HSE) and planning regulations. In addition, some planning authorities require liquid storage facilities to have bunding around storage silos for spillage safety. Regulators may also require spillage and leakage detectors to be in place and monitored. When stored, operators should be aware that sediment in the digestate will settle out and will need to be stirred or agitated to ensure homogeneity before application or transporting. Due to the impermeable nature of roof structures and flexible covers, specialist design may be required to allow access for agitation equipment. With flexible covers, care needs to be taken to avoid mechanical damage during agitation.
Reviewed literature relevant to the task work shows that the solid fractions obtained with the separation methods presented in Task 4.1 consist of relatively high percentage of liquid. Unless directly applied as biofertiliser, it would require appropriate storage until the season for use as fertiliser or soil improver comes. If the solid fraction is to be used as a stable and marketable product, however, further processing in the form of composting and drying will be required. This is because solid fraction with high liquid content still contains biodegradable material that may stimulate microbial growth and odour emissions. The most common method of storage used is flexible polyethylene bags, but tanks covered with gas tight metallic plates or membrane can also be applied.
Transportation will be required when the land to which digestate is to be applied is not adjacent to the AD plant. Transporting digestate over long distances is expensive, and so availability of land should be considered in the early stages of planning an AD plant, particularly if the plant is located in an urban setting. If digestate disposal becomes necessary, for example liquids for treatment or solids to landfill, for even a proportion of output, it can have a huge impact on
business viability.
Solid digestate can be transported by truck and stored on fields under a rainproof cover prior to application. As a rule of thumb, dewatered cake from wet AD systems will require only 20% to 30% of the vehicle movements required for liquid digestate.
In relation to environmental and health impacts, the AD plant management, the landowner, the recycling team and the transport company should be regarded as equal partners in any digestate-to-land programme. All can be ultimately accountable to national and regional regulators and the acknowledgment of this fact is vital to the success of the operation.
Stabilisation by composting: During composting available microorgansms degrade and transform the organic material under aerobic conditions to compost. The compost is stabilised organic matter, containing humic substances. As biofertiliser the compost slowly releases nutrients and shows good performance as soil improver. However, as the solid fraction from digestate is wet and already partially degraded, the addition of bulking material such as woodchips is necessary for obtaining a stable composting process. Addition of bulking material helps to enrich the compost with air and enhancing and maintaining aerobic conditions. If a centralised composting site is available, it would be advantageous to do the composting at such centralised facility. Composting of the solid fraction generally increases the concentration of nutrients, but it may at the same time result in nitrogen loss.
Stabilisation by drying: When the solid fraction of digestate is subjected to drying, stabilisation of the product and reduction of the total mass as well as increase in the nutrient concentration is obtained. Drying can take place utislising the excess heat in a CHP unit. Different drying techniques can be applied including belt dryer, drum dryer, feed-and-turn dryer, and fluidised bed dryer. The most common technique for drying digestate is application of belt drying. Another common alternative is solar drying during the warm season. As the exhaust of the digestate dryers contains dust, ammonia, and other volatile substances such as volatile acids, exhaust gas cleaning systems have to be installed.
Use of solid fraction: The solid fraction of digestate can be used in different applications substituting industrially produced mineral fertilisers. Applications include use as bio-fertiliser for crops, soil conditioning, landscaping, horticulture, as home garden product and pellet fertiliser. Many of these applications require, however additional processing.
The three basic nutrients that are required in any fertiliser or soil conditioner are Nitrogen (for leaf and stem growth), Phosphorous (for root growth) and Potassium for flowers, fruit and health growth. Most commonly used feedstocks in AD such as animal manure, blood, fish and bone have however a low nitrogen value and therefore may have limited potential to productivity on their own. As a result, they must be combined with other, more nitrogen-rich materials (or mineral fertilisers). On the other hand if solid digestate is used consistently the results are increased organic matter in the soil, improved water filtration, reduced erosion and increased biological activity.
Solid digestate can be composted to act as a suitable soil improver in horticulture. However, digestate many not be the most appropriate alternative in certain horticulture areas. For production of fruit, vegetable, trees and shrub the nutritional values of digestate require supplementing to be sufficiently useful. It could also be sold bagged to home gardeners in the same way as any other compost, with good outcomes for the gardens and the environment.
There are a number of pellet products available with varying intended uses. These included slow release inorganic vegetable fertilisers, rose and shrub feeds, root boosters and multipurpose organic fertilisers. In order to compete with these products, however, digestate needs to be thermally dried and pelletised. From a nutritional perspective solid digestate has a higher nitrogen level than currently available products, although it typically has lower levels of phosphorous and potassium.
Fertilizer quality growth trials:
The nutrient content of the liquid digestate was strongly determined by the component mixture for anaerobic digestion. NPK were present in all digestates, but N was only present as ammonium nitrate and not detectable as nitrate nitrogen. The inclusion of marine aquaculture waste resulted in elevated levels of sodium. Ammonium nitrate is a more volatile source of nitrogen and may be less available for plant growth in the presence of sodium ions. The inclusion of cattle waste as a component of reactor mixtures elevated the presence of plant micronutrients.
The inclusion of fish cuttings in the mixture combinations in this study did not substantively alter the nutrient content of the resultant digestates.
Plant growth trials assessed the value of liquid digestate as a plant fertilizer for two species (Hordeum vulgare and Lolium perenne) during the vegetative stages of growth. In both plant species, responses to increased nitrogen applications as inorganic commercial fertilizer were observed with maximum yields of biomass in both species up to 100 Kg N / ha, affirming that the experimental growth trial system was adequate.
In H. vulgar, using both marine and freshwater based digestates as liquid fertilisers, no significant differences in yield responses were observed in either dry biomass or as total leaf length over an application range up to 100 Kg N / ha at the late vegetative stage (maximum tillering). Yield responses to the nutrient content of digestates derived from differing mixtures were not significant.
In L. perenne, there was no significant response to digestate nutrients derived from mixtures of freshwater based aquaculture waste when applied at 100 Kg N / ha, a rate which gave maximum yield when applied as inorganic nitrogen. Contrastingly, growth responses in relation to marine based aquaculture waste indicated suppression of growth when digestate was applied at rates giving over 50 Kg N / ha.
5. CONVERSION AND DISTRIBUTION OF BIOGAS:
In the work related to options for use and sale of biogas, the topics that have been addressed include the need and means of biogas storage, biogas distribution, use of upgraded biogas as biofuel, cleaning and upgrading of biogas and available technologies, technical and economic evaluation of upgrading methods and distribution of bio-methane. The outcomes are meant to be a component of the BiFFiO best practice to be implemented by the end users.
Biogas storage: In most cases, biogas is used in combined heat and power applications (CHP) that combust the biogas to generate electricity and heat for on-farm use. The electricity is typically produced directly from the biogas as it is created, although the biogas may be stored for later use when applications require variable power or when production is greater than consumption. Biogas that has been upgraded to biomethane by removing the H2S, moisture, and CO2 can be used as a vehicular fuel. Since production of such fuel typically exceeds immediate on-site demand, the biomethane must be stored for future use, usually either as compressed biomethane (CBM) or liquefied biomethane (LBM). Because most farms will produce more biomethane than they can use on-site, the excess biomethane must be transported to a location where it can be used or further distributed. As the principle for storage of biomethane and biogas are similar (even though the size, safety, pressure and material type various), storage of both products is addressed in the same section.
The two basic reasons for storage of biogas and bio-methane are: storage for later on-site usage and storage before and/or after transportation to off-site distribution points or systems. The least expensive and easiest to use storage systems for on-farm applications are low-pressure systems; these systems are commonly used for on-site, intermediate storage of biogas. The energy, safety, and scrubbing requirements of medium- and high-pressure storage systems make them costly and high-maintenance options for on-farm use. Such extra costs can be best justified for biomethane, which has a higher heat content and is therefore a more valuable fuel than biogas.
Distribution of biogas: Biogas can be transported using the same methods as for natural gas, either in piping systems or in gas cylinders. If the biogas is to be injected to existing natural gas grid, upgrading to natural gas quality is required. However, there is no requirement of upgrading if the biogas is to be transported by own piping system. Transport in cylinders takes place under pressure, i.e. as compressed biogas (CBG) or liquid biogas (LBG), CBG is suitable when transporting relatively small amount of gas over short distances and is the most commonly means of transporting biogas. The gas cylinders are mounted on a truck and are filled with the gas under a pressure of 300 bar.
For transporting biogas as LBG, the gas must be first cooled down to -162 °C. Then it can be transported by LNG trailer truck or a tanker. Whereas a CNG (compressed natural gas) truck can transport about 6000 Sm3, per trip, a trailer truck with liquefied gas can transport about 32000 Sm3 of gas in the same trip. For small and medium sized biogas plants, production and distribution of CBG is more cost effective. For plants that have capacity in the order of 60 GWh or higher, it can be worthwhile to consider distribution in the form of LBG. The advantage of transporting LBG also increases with increased transport distance.
Distribution of bio-methane: Biomethane can be distributed to its ultimate point of consumption by one of several options, depending on its point of origin:
• Distribution via dedicated biomethane pipelines
• Distribution via the natural gas pipeline
• Over-the road transport of CBG
• Over-the-road transport of LBG
Use of upgraded biogas: Raw biogas has a low energy density and can contain corrosive impurities that makes it not applicable to ordinary burners, engines and transporting systems. With further upgrading treatment involving removal of CO2 and other impurities, the gas can replace or supplement the non-renewable natural gas in most cases. After upgrading of the biogas to natural gas quality, the biogas (biomethane) can be used in vehicles that are adapted for running with gas, i.e. both cars, busses and ferries. Currently, there are 3 different types of vehicle engines that use gas as fuel:
• Dedicated gas engines (use only gas as fuel in the form of CBG or LBG)
• Bi-fuel engines, use can use two types of fuel (gasoline and gas) with gasoline as back up
• Dual –fuel engines, use two types of fuel simultaneously (diesel and gas). While driving outside cities with even speed, 80-90% of the fuel used is gas, while during city driving the percentage of gas consumption can be reduced to 75-80%. (IBID)
When biogas is used as a substitution to diesel and gasoline as fuel in vehicles, it contributes to lower emission of GHG. Moreover, there are other advantages including reduced emission of particles (nearly zero) and NOx in the exhaust gas from gas driven vehicles.
Cleaning and upgrading of biogas: As an outcome of the task work, cleaning of biogas is defined as the process in which impurities (undesired gas components) in the raw biogas are removed either to avoid corrosion in pipelines and other equipment, toxic substances such as H2S and risk of explosion, whereas upgrading of biogas is the process by which carbon dioxide is separated from the biogas to enhance the energy yield. Some upgrading methods both clean and upgrade the biogas, while other methods require a comprehensive pre-cleaning. The impurities in in this regard and require cleaning include water, H2S, oxygen, nitrogen and ammonia.
Biogas upgrading: Biogas to be injected to a natural gas grid, or used as biofuel has to be upgraded to a natural gas quality. The requirement of biogas quality for fuel purposes are not finite or absolute and there is no unified European quality specification set for bio-methane. There is however the Swedish standard of > 95 % methane content that is used in many countries. Moreover, the International Organization for Standardization has made a standard called “Natural gas for use as compressed fuel for vehicles – Part 1: Designation of the quality”. This standard is also used for upgraded biogas and regulates methane content to a minimum of 96 Vol-% (Deublein & Steinhauser 2008). In addition, it sets limitations for the contents of hydrogen sulphide, total sulphur, carbon dioxide, oxygen, hydrocarbons and water.
For addressing the need of cleaning and upgrading biogas, a number of methods have been developed. The most developed and widely used ones include: Pressure swing adsorption, Membrane separation, Water scrubbing, Organic physical scrubbing and Organic chemical (Amine) scrubbing. The principle of operation of these methods is presented in Deliverable 5.1 Part A, Section 5.8.
In the task work, technical and economic evaluation of the upgrading methods has been undertaken based on literature review. The outcome of the evaluation is presented in Deliverable 5.1 Section 5.9 and 5.10.
Activity and Results of case studies: The following data were collected for modelling AD plant feasibility by questionnaire, telephone canvassing and visits to SSPO and BTA members.
Location of farm, the volume of waste produced, the variability of the volume of waste (seasonal? Max, min per week), nature of waste: slurries, processing waste, cuttings, mort; current storage capacity for waste(s); current disposal pathway and cost of disposal , possible uses of slurry/digestate. Potential local uses for heat on site or close by. Are there any space restrictions for storage and installation of plant or other local restrictions, considerations or barriers?
Further data was compiled or estimated from our results:
• Physical/chemical data of the slurry
• Total solids/Volatile Solids of waste
• Bio(gas)/(methane) potential
A spreadsheet was constructed for each farm and the closest scenario to the nature or mix of waste streams available was used to estimate gas outputs to give volume (or equivalent) of methane gas produced, raw/total power, an estimate of parasitic load, the maximum (exportable) electrical power and thermal power (using all of this raw energy), applicable FIT and reactor size, maximum exportable electricity (100% of energy converted to electricity, assuming 30% generation efficiency) and thermal (100% of energy converted to heat), assuming a 65% boiler efficiency. For animal products, the pasteurization cost was calculated as the total cost of increasing temperature to 70°C from ambient but no account was made for maintaining that temperature for one hour.
UK Feed in Tariffs were used for “cash” calculation, however the most efficient use of electricity was assumed to be use on site, thus reducing cost of buying in electricity. Data were collected for over 10 farms and a selection of four, representing the sector were developed as case studies.
6. BEST PRACTICE
The results from the scientific and technical work in WP1-WP5 of the project have been assimilated into a best practice guide or reference document. The intention is to develop an output to be used by the end users in management of aquaculture and agriculture waste in a sustainable manner. The guide is prepared as Deliverable 6.1 that also includes the material used for training of the trainers..
For economic evaluation the BiFFiO best praactice, an assessment has been made regarding the policies in the countries that are represented by the SMEs towards both biogas production and use of digestate generated by by anerobic digestion in order to define the boundary conditions for the economic evaluation. Further to this, the task work has looked into existing divers and barriers for access to feedstock, production and use of biogas as well as use of generated residue from anaerobic digestion. As a tool for use in the economic evaluation a model has been developed for calculating the economic benefits of using the BiFFiO best practice based on the revenue and cost factors.
There are diverse policies in the different countries even though the sum of the drivers and barriers in Germany and Norway as well as the other Scandinavian countries more or less similar. There is also price difference of energy between the different countries. Therefore the model has used average specific prices, for example transport and electricity. There is also big difference in development of grid for distribution of gas, for example between the UK and Norway as the main source of energy production in Norway is hydropower. However, upgrading and sale of biomethane is not considered in the economic evaluation as the consortium considered this element of biogas production slightly remote for the SME-AGs. Moreover, studies made on the economic potential of upgraded biogas in Sweden has shown that there is no profit unless there is sufficient government incentive.
Risk Assessment and Contingency Management:
This task has included the close monitoring of the progress in the different RTD WPs in order to ensure coordination and integration of the technical activities and solutions in the production process from pre-treatment to use of bioenergy and digested matter. Special focus was being given on the interface between the different WPs, especially the interface between WP2 Pre-treatment, WP3 AD technology and WP4 Post treatment – Separation and handling of digested matter. Further close focus were be given for WP5 and the feasibility study of the conversion and use of biogas. TI, as the task leader and coordinator of the BiFFiO project, has closely monitored the progress in these WPs. The monitoring was carried out by having frequent RTD meetings and planning for the best integration between WP 2, 3 and 4. As an example, there have been several discussions and planning for post-treatment process, even though the WP 4 has not started formally. Contingency management for WP - 2, 3 and 4 was conducted to ensure good interface between them.
The development of technology and best practice in WP2, WP3 and WP4 have undergone risk assessment by close monitoring of progress in the different work packages and their inter-relationship with the entire project. Likelihood of failures within work packages and tasks have indicated and evaluated and the likely tolerance band for under-delivery assessed. Corrective actions were initiated if required reassessing the cumulative effect of the changes on the predicted tolerance band of the major element deliverable and confirm that this is acceptable in relation to the overall project objectives. A corrective action was to continually running the test for pre-treatment and integrates it with the WP3 trial. There may be some re-iteration for some of the tasks with changes to their content that are likely to produce an improved deliverable closer to the quantified target. The improved deliverable will then be re-integrated into the milestone assessment.
Contingency planning to ensure that the operational goals are met was considered specifically at work package level. WP2: in case equipment fails to meet the quality or performance criteria, prepare SoA alternatives for feed production suitable for testing of bioreactor performance in WP3. WP3: In case own pilot reactor equipment fail to meet the quality or performance criteria, deploy a lab-scale or similar test alternative for testing of bioreactor performance, and provide biogas and sludge for post-treatment use in WP4. WP4: In case separation or novel absorption technology fails to work properly, design other laboratory tests to document the quality and valorisation potential of digested matter.
Potential Impact:
The BIFFIO project will contribute towards compliance with EU directives, policies and acts such as Nitrate Directive (91/676/EEC, Environmental Protection Act (2000/86), Government Decree No 931/2000), Water Framework Directive (2000), and Groundwater Directive (2006), the common agricultural policy, Council Directive 86/278/EEC of 12 June 1986). Environmental impact can, by using the BiFFiO technology, be reduced in terms of reduction in GHG emission, nutrient run-off and unwanted odour and improvement of sanitation and hygiene. The aquaculture and agriculture industries can use BIFFIO as an inventive way to take economical advantage of the potential use of their waste products and in turn reducing their emissions, runoffs and waste handling costs.
The BiFFiO project will provide technological solutions and best practices useful to an extensive number of European SMEs within the agriculture, aquaculture and bioenergy sector. Both the aquaculture and agriculture industries face regulatory and social requirements for the waste produced in addition to the fact that the aquaculture industry has an energy need which can be assisted by production of biogas from the waste.
A possible positive return on investment for the farms will encourage use of the new best practice and purchase and use of the BiFFiO reactor technology. An estimated 3 years pay backs seems attractive to farmers. A lower cost level like this will make it considerably easier for the aquaculture and agriculture industries to use biogas production as a method to handle their waste issues.
The BiFFiO project has as one objective to recover nutrients during the process. The farmers will hence be able to reduce their need to purchase fertilizers and reduce their costs. In addition, any excess nutrients can be sold on the market, creating an income. There is a growing acceptance that an increased amount of nutrients via manure processing must be exported from regions with surplus nutrients to regions low in nutrients.
Both in Europe and internationally, animal manure is a significant contributor to the GHG emission in the form of methane and nitrous oxide. Application of the BiFFiO best practice would contribute to mitigation of green house emission by utilising the manure as source of renewable energy. Additional benefit is retaining the nitrogen in the manure as a nutrient rather than its loss when converted to ammonia and nitrous oxide. An indirect societal and environmental benefit is substitution of fossil based energy by energy based on renewable source. Further to this, utilisation of fish waste including cuttings contributes to supplementing the depletion of phosphorous that is becoming a scarce commodity.
Use the biogas as upgraded biofuel substitutes fossil based fuel contributes to reduced GHG and NOX. Use organic fertiliser generated by the BiFFiO best practice has also indirect value as it reduces the need for production of inorganic fertiliser and associated emission of GHG.
List of Websites:
Website address: www.biffio.com.
Contact details: Mr. Mezmur Shiferaw, Email: mezmur.shiferaw@ti.no. Phone: +4795818829.
Mr. Morten Berntsen, Email: morten.berntsen@ti.no. Phone: +4798290366
BIFFIO is a project within Research for the Benefit of SMEs in which the research work is funded by the European Union’s FP7 administered by the Research Executive Directorate (REA). The project was officially started on November 2013 and has a duration of 39 months. BiFFiO is an example of industrial symbiosis, initiated from aquaculture, agriculture and renewable energy industries for a sustainable waste management by producing renewable energy from mixed aquaculture and agriculture waste, in addition to production of fertilizer. The consortium consists of eight SMEs/AGs, and three RTD performers.
The project addresses the challenge which aquaculture and agriculture industries face in respect to regulatory and societal requirements for the waste produced, an issue which is in need of sustainable solutions. A great majority of aquaculture farms are located in remote areas, close to agriculture activity where large scale biogas plants are not a good fit based on the amount of waste produced and high cost of long-distance transport. This limitation has emphasized the need for the cross-sector approach chosen in for this project, where local livestock and fish farms can combine their waste and collectively take advantage of the end- products in a plant scaled to meet the demands for their specific waste needs.
Thus, the main objectives of BiFFiO are 1) Development of a new best practice and novel technology for handling mixed waste from aquaculture and agriculture for production of energy, and use of the digested waste, 2) Development from current large scale SOA technologies for treating animal waste, to an economical, efficient and scalable three-stage system of pre-treatment, biogas reactor and fertilizer recuperation; 3) Application of new technology in the agriculture industry alone or together with fish farming industry, 4) Impact on socio-economic conditions through the benefits of improved hygienic and environmental. standards of closed fish farming and by reduced greenhouse gas emissions and other pollution burdens from the agriculture sector.
Project Context and Objectives:
The concept of the BiFFiO project is to mix the waste readily available from fish farms and manure waste from the agriculture industry in a reactor for production of biogas, which in turn can be used to fill the need for renewable energy in the aquaculture industry and supply fertilizer products to the agriculture industry.
A great majority of aquaculture farms are located in remote areas, close to agriculture activity where larger-scale AD plant solutions is not a good fit based on amount of waste produced and distance of
transport of waste. This fact limitation emphasizes the need for the cross-sector approach chosen in for this project, where local livestock and fish farms can combine their waste and collectively take
advantage of the end products in a plant scaled to meet the demands for their specific waste needs.
Using fish waste together with manure from animal production will boost the biogas production versus using manure or fish waste alone, providing a benefit to both industrial sectors. The BiFFiO project partners, representing the aquaculture, agriculture and renewable energy industries, hence see a great opportunity in production of renewable energy from mixed aquaculture and agriculture waste. The partners will develop energy efficient, cost effective, easy to implement and easy to operate biogas reactor technology. The reactor will be based on high-rate anaerobic digestion (AD) and will be designed for recovery of valuable biogas and nutrients from the digested waste, thus reducing pollution and emissions.
There is a need for sustainable solutions to handle the waste which is produced as part of the daily
production in both the aquaculture and agriculture sectors. This project will contribute to providing sustainable solutions by converting waste into renewable energy and valuable end products that will benefit the European aquaculture and agriculture industries.
This new biogas technology will facilitate a new best practice for handling combined waste from aquaculture and agriculture by:
• stabilizing the organic matter
• reducing odours and pathogens
• controlling physical and chemical contaminants
• providing recyclable end products in the form of biogas and digestate
As the aquaculture industry is moving towards increased use of recirculation aquaculture systems
(RAS)1 and is exploring the use of closed fish cages at sea, the industry needs new technology for
sustainable handling and utilization of the fish faeces and waste. Presently, fish farms have to store the sludge for further treatment2 this creates challenges such as odour issues and handling costs. Production of 1kg biomass (fish) generates approximately 180g of fish faeces3, 4. Based on annual fish production in Europe, there is a total production of approximately 454.172 t fish faeces in Europe per year (FAO). In traditional flow-through fish farming facilities the production of waste products could cause environmental problems like excessive oxygen depletion and increased algal growth. Especially in sheltered or closed coastal areas and waterways the action of coastal currents can be insufficient to dissipate the wastes. Therefore, in order to increase overall production, while minimising the impact on the environment and complying with environmental regulations, land-based RAS systems and closed-cage fish farms are emergingHowever, the collection of fish faeces and waste represents a cost for the fish farms in form of handling and transport. Further, although RAS systems reduce the negative impact on the water environment by collecting waste, they consume more energy to support water circulation to the stock than the technology they replace. A potential solution is the development of new technology that can utilize the fish farm waste to generate the energy required, thus reducing the carbon footprint of the aquaculture industry. Likewise, as agricultural industry is intensified and the price of inorganic fertilizer continues to rise, livestock farms will need new sustainable methods for handling the excess manure and redistributing the organic manure fertilizers. The livestock sector is also a high contributor to greenhouse gas (GHG) emissions, which highlights the need for improved, more sustainable approaches to livestock production. High livestock density is accompanied by production of surplus animal manure. This represents a significant, localized pollution threat. Excessive fertilization of arable land can damage the environment and is not economical since valuable nutrients used in excess are
generally washed into waterways. Intensive animal production will benefit from suitable manure
management facilitating export and redistribution of excess nutrients from manure and optimize
nutrient recycling.
The EU has fixed a goal of supplying 20% of the European energy demands from renewable energy
systems (RES) by the year 2020. A major part of this renewable energy will originate from European farming and forestry. At least 25% of all bioenergy in the future is likely to originate from biogas, produced from wet organic materials such as: animal manure, whole crop silages, wet food and feed wastes, etc. Therefore, there is a pressing need to develop economical technologies that enable production of renewable energy for smaller fish and animal farms in rural areas.
The BiFFiO project will enable SMEs from the aquaculture, agriculture and energy sectors to
increase the sustainability of their production, and by finding economic viable solutions for
handling waste products, will help increase their competitiveness. The initiators of this
project: the Scottish Salmon Producer Organisation (SSPO) and the British Trout Association
(BTA), representing SMEs in the fish farming industry, have recognized the urgent need for
collaboration and further R&D to find economic and functional solutions for sustainable use of fish wastes. Landberatung GmbH (Landberatung), the European Biomass Association (Aebiom) and Norsk Bioenergiforening (Nobio), representing the agricultural and bioenergy SMEs, see the wealth of opportunities for improved utilization of waste products by combining the waste sources from fish and animal farming. Included in the consortium are OTHER-SME partners that can produce, deliver and distribute the BiFFiO technology to the market post-project, namely: Awite Bioenergie GmbH (Awite), OÜ Kalavesk ltd and Aqua & Waste International GmbH (a&w) delivering turn-key technologies for water, wastewater,
environmental and renewable energies. As it is difficult for the associations representing the SMEs, and the actual farms themselves, to finance and run R&D activities, the EU scheme for Research for the benefit of SMEAssociations is a suitable platform, enabling outsourcing of the RTD activities essential in the BiFFiO-project. Thus, the initiators have engaged Aqua Consult Ingenieur GmbH (ACI), University of Liverpool (UoL) and Teknologisk Institutt as (TI) to perform the RTD tasks in the project.
The European aquaculture industry employs approximately 80,000 people, equivalent to 3.3 per
10,000 of the active population5, but is dominated by SMEs. The agricultural sector, which provides
approximately 6.6% of the total employment in the EU region6, is likewise dominated by SMEs. Thus,
these two industries represent very large groups of SMEs with great importance to Europe. The
majority of the SMEs in these industries are located in remote areas where large-scale AD plant
solutions are not a good fit based on amount of waste produced and distance of transport of waste.
This limitation emphasizes the need for the cross-sector approach chosen for this project, where local livestock and fish farms can combine their waste and collectively take advantage of the end products in a plant scaled to meet the demands for their specific waste needs.
The idea of the proposed project is to use a high rate biogas reactor to treat the waste. High rate biogas reactors are available in various designs, e.g. the up-flow anaerobic sludge bed reactor (UASB). With very few moving parts, apart from circulation pumps, anaerobic bio-processing is robust, provides scalability down to small units, and poses low energy and maintenance costs. The sludge production is about 1/10th of aerobic treatment. Diatomaceous silicate and bauxite aluminates have proved very efficient absorbents for the water-soluble inorganic phosphorous accumulating in the water-phase following a biogas treatment. A second treatment stage will harvest Phosphorus (P) and ammonium-Nitrogen (N) in a bioavailable form to support plant growth.
Following hygienisation, the biogas sludge and absorbent sludge will be usable and saleable products for soil amendment. The solution for handling the waste stream will be cost-effective, functional, sustainable, and facilitate production of useful end-products for use in the agriculture sector. The digested waste will be made suitable for storage and used as fertilizer. Analyses show that fish faeces have relatively high bio-methane potential and a particularly high content of phosphorous compounds7 and, therefore, represents a potential source for biogas production as well as a valuable source of nutrients for fertilizers or for other uses. Life cycle assessment demonstrate that the most energy efficient and climate friendly approach is to recuperate energy from the waste by biogas production and harvest the nutrients (N, P, K) from the combined waste. Using fish waste together with manure from animal production will boost the biogas production versus using manure or fish waste alone, providing a benefit to both industrial sectors. Case studies demonstrate that, even in a very high energy efficient recirculation farm, the biogas potential of the fish faeces produced “on site” represents a maximum of 8-10% of their total energy requirement7. Anaerobic digestion of animal manure and slurries offers several benefits by refining and enriching their fertilizer qualities, greatly reducing GHG emissions, reducing odours and pathogens and producing renewable fuel like biogas. Although advanced biogas reactors are in use in Europe, the existing technology is neither developed nor scaled to handle the waste from fish farms in an economic, robust and user-friendly way. Thus, is a need for further innovation of biogas production solutions for use in fish farming and agriculture in remote areas... The fish farming activity is often located in more rural areas as are the agriculture sector. In order to have a higher amount of energy coming from biogas at fish farms, cooperation with a second supplier of a waste source for biogas production is called for. Cooperation between the aquaculture and agriculture sector is especially interesting since the agriculture sector has readily available sources such as manure for biogas production. Further, a regional cooperation between the aquaculture and agriculture sectors ensures short transport distances.
Main Project Objectives:
1) Development of a new best practice and novel technology for handling mixed waste from
aquaculture and agriculture for production of energy, and further use of the digested waste.
2) Development from current large scale state-of-the art (SoA) technologies for treating animal waste, to an economical, efficient and scalable three-stage system of pre-treatment, biogas reactor and fertilizer recuperation, which can be located at or in the vicinity of most near shore and on-shore closed fish farm operations.
3) Application of new technology in the agriculture industry alone or together with fish farming
industry, on both remote and central locations to save costs for waste transport and deposition.
4) Impact on socio-economic conditions through the benefits of improved hygienic and environmental standards of closed fish farming and by reduced GHG emissions and other pollution burdens from the agriculture sector.
Operational goals:
To greatly increase biogas yield from combined waste, major reduction of reactor volumes by highrate technology, lower investment costs per volume of biogas produced, elimination of hygienic hazards, optional full coverage of fish farm energy needs in terms of electricity and heat from combined fish and other waste, and add value to both industries by return of fertilizer and soil
remediation products of cropland quality.
Project Results:
1. DESIGN CRITERIA:
For waste composition analysis, samples were taken from two representative cattle farms: Wood Park is a medium sized dairy, high intensity farm where most of the cattle are housed indoors. Ness Heath is a small beef farm with a small herd of pedigree Herefords kept mainly outdoors on pasture. These represent extremes of a scale. Laboratory analyses were carried out to define and characterise the physical (moisture content, particle size, degradability), chemical, and biological characteristics (including biodegradability, nutrient content and the presence of potential contaminants). Determinands were: Total Solids, Particle size, n-Caproic acid, Acetic acid, Propionic acid, Iso-Butyric acid, N-Butyric acid, Iso-Valeric acid, N-Valeric acid, Iso-Caproic acid, Acetic acid, total Nitrogen, Ammonium Nitrogen, C.O.D. (fresh), Volatile Solids and pH. The samples were assessed in-house for copper, iron, arsenic and lead, however, all levels, as expected in agricultural manure, were lower than our routine analysis (safe levels) could determine: 1mg/l Cu, 0.05 mg/l Fe, 0.2µg/l arsenic, 20mg/l Pb.
Fish farm waste was sampled from four aquaculture facilities: two Salmon hatcheries in Scotland and two trout farms in England. Marine Harvest Lochailort is a large, modern facility with a yield of 15 to 16 million fish. >60 tonnes of waste is collected per week and spread on local farms. Tullich is smaller - 10-12 tonnes of solid waste is generated each year and spread on local fields. Chirk only stocks rainbow trout. Waste is pumped into settling ponds and left to dry and eventually used as manure for local fields. Kilnsey Trout Farm is a fly fishery and trout farm. Waste sediments sink to the bottom of the tanks and the clean water flows out. This is then spread onto fields within the park estate. The Total Solids varied between 0.22% and 18.7% in fish farm waste and 4% and 19.2% in cattle waste (Marine Harvest pre- dewatering and filtering is 2% solids, rising to 19% solids post- filtration). For the cattle farms, raw waste from Wood Park farm from the slurry lagoon had a total TS content of 4%. We estimate the C:N ratio of our fish waste to range from 9:1 – 11:1 in Marine Harvest samples, to 12:1 – 16:1 in the Kilnsey samples. In the cattle manure, the C:N ratio varies from 2:1 in Ness Heath to around 20:1 in the Wood Park. This is likely to vary over the year, with forage type, and undigested feed components (such as grains). pH varies in these manure samples – generally lower in the aquaculture samples (pH 5 to pH 6.9) and higher in the cattle samples (approximately pH 7 in the Wood Park Main samples). Anaerobic digestion is favoured within parameters pH 7 to pH 8.5 therefore, it may be necessary to buffer the pH of the feedstock.
The samples of slurry from the dairy and beef farms and from the fish farms were analysed and results presented in the D1.1 report and discussed with partners at RTD and Management meetings. We drew the following conclusion. The slurries and manure examined fall within normal/expected parameters. The range of TS values cover a sufficiently wide range, both within individual farms and across farms, to provide great scope for “designing” feedstock compatible with a wide range of AD technologies. The pH ranges measured are lower than ideal, therefore pretreatment or intreatment buffering to raise the pH. The consensus was that Continuously Stirred Reactors with buffering and a facility for daily renewal of feedstock was a simple design that offered flexibility and a high likelihood of success in using these slurries as feedstock. Volatile Solids and C:N ratio data suggest that the manures and slurries examined have good biogas potential.
The safety issues regarding biogas have also been investigated. For this, the process complexity, the usage of biogas and possible explosion zones on biogas plants has been examined.
In order to map the main hazards related to the usage of the end product, the legal definitions have been researched and the main hazards related to the usage of the digestate as fertilizer and for animal bedding have been investigated.
After this the related legal and safety issues regarding the usage of the end product are described and aspects regarding the localisation of a biogas plant are discussed. Finally a risk assessment for a biogas plan was done.
Regional benefits and restrictions:
A general research regarding EU-regulations,-directives and -decisions has been conducted. In addition to this TI, UoL and ACI did a research at their home countries regarding the implementation of the found EU regulations and further national laws related to biogas or waste from aqua- and agriculture.
Handling strategies:
In order to define handling strategies research has been conducted regarding possible factors (e.g. composition of the sludge, sulfate- and salt-concentration) influencing anaerobic digestion of waste streams from brackish/marine RAS. Furthermore possible reactor types have been investigated for the anaerobic digestion of aqua- and agriculture waste.
With the help of SME-AGs and their members, we were also able to map logistic challenges, define best solutions and identify criteria for biogas process design at actual fish farm and farm land sites in selected countries that SME-AGs have their members. The work consist of; 1) Literature and publication search for relevant information. 2) Questionnaire to be distributed to members of the SME-AGs. 3) Interview questions to be asked to selected end users, which are members of the SME-AGs.
The literature study and the survey show that there is a great potential for aquaculture farms to collaborate with their agricultural farms in neighborhoods and install one biogas plants in the vicinity of their farms. This can be economically efficient by looking into the energy and waste handling costs that these two sectors are nowadays dealing with.
In the studied agriculture farms , based on questionnaire and interviews, average results shows that 100-500 livestock units are kept and farms are using approximately 50 MWh/year which costs about 10 000 £/year. Farms are using electricity from the grids primarily and use diesel or oil as a secondary source of energy. A typical studied farm uses more that 50% of the energy for heating/cooling. They are collecting approximately 750 tons of manure per year and mostly use it as fertilizer on lands.
In the studied aquaculture farms, based on questionnaire and interviews, average sizes of the farms are between 1000-5000 m3 with around 1-5 million annual fish production. They use 100-500 MWh/year which cost around 100 000-500 000 £/year. Farms are using electricity from the grids primarily and use diesel or oil as a secondary source of energy. These farms are producing fish feces and uneaten food waste about 20-100 tons/year. This amount of waste has a cost burden for transport and waste handling of about 1000-5000 £/year. The interviewed company has analyzed the biogas potential of fish faeces and found it unprofitable. They claim that acceptable payback period for them is about 3-7 years. In addition, there is no governmental support for using their waste in biogas plants.
Interview was made with a biogas plants owner with CSTR reactors with the feed of waste silage and solid pig manure. The plant is handling 5475 tons per year and in return produces 130500 Cubic Meters of Biogas. They can accept cattle slurry of 9-11% dry matter but not interested to accept fish waste because they need to get permission. From literature study, input of 4418 tons per year (4380 tons of cattle manure which is co-digested by 37.5 tons of maize crushed grains), leads to electric energy gross production of 327 MWh per year.
2. PRETREATMENT TECHNOLOGY:
A vital component of feedstock pre-processing is to evaluate the current available SoA pre-treatment options and select the best method(s) for the waste characterized in WP1, and fulfill the required and preferred properties to be run in a high-rate anaerobic reactor in WP3 (UASB and CSTR) at mesophilic conditions. The selection of the pre-treatment methods is based on economic consideration – cost versus benefit, robustness, safety and practical issues, like user friendliness and functionality.
An overview of the benefits and disadvantages of each method was presented in the deliverable 2.1. Based on the evaluation study and input from partners, the pre-treatments with the highest potential for the most optimal final result is selected, considering cost benefit, potential increased biogas production, user friendliness, robustness and improvement of digested matter.
Regarding these criteria, different pre-treatment methods were evaluated and selected for further testing at the BiFFiO pilot plant. The evaluated methods were dewatering (stepwise filtration, screw press, decanter centrifuge and sedimentation), particle reduction (grinding, cutting and macerating), ultrasonic treatment, acid, alkaline and metal salt addition, enzymatic hydrolysis, thermal (conventional, microwave and steam explosion) and combined methods (FSPM and flocculation and sedimentation). Among these treatments the selected methods for further testing where:
• Sedimentation (for dewatering)
• Maceration and grinding (particle reduction)
• Thermal heating (for hygienisation)
• Mixing (to ensure consistency).
The selected treatments has the advantage to make the feed easier to handle for the system, but will also give additional advantage as increasing biogas yield, potentially reducing AD inhibitors, hygienisation and reduce energy demand.
Based on the evaluation and selection of appropriate pre-processing methods, the pilot unit was installed at the School of Veterinary Science University, University of Liverpool. The entire plant consists of two containers, where the pre-treatment process and laboratory occupies one of them. The three sedimentation tanks are integrated outside the containers. In the pre-treatment-container there are work benches where the equipment is installed. Duo to practical and economic reasons, small scale equipment and simple food processor machines were applied.
The available pre-treatment equipment at the BiFFiO pilot plant are:
• 1 pressure boiler for thermal treatment and hygienisation
• 1 small oven for drying preparation for total solid measurement
• 1 kitchen machine with a food processor for cutting/macerating
• 1 industrial mixer unit for blending
• 1 scale for weighing
• 1 meat grinder for grinding the fish cuttings
• 3 water tanks for sedimentation of saline fish sludge, freshwater fish and manure sludge
• A number of pipes to transport sludge, connecting the sedimentation tanks to the pumps
• 2 Pumps for loading and unloading
• 6 barrels for storage
The pre-treatment processes will operate using a batch system and the sludge would be transported between unit operations by pumps and manually in buckets by the operators. The pre-treatment methods where integrated at the pilot plant in Liverpool during November 2014 and finalized in December 2014.
In the pre-processing of animal slurry collected from the farms, the slurry is first stored in intermediate bulk containers (IBC). Waste in the IBC is stirred with paddle mixer according to the procedure described in Deliverable 2.1. Portion of the waste is first transferred to a clean , labeled bucket. Samples of 1,5L are decanted then decanted to a blender. After blending, coarse particles are removed by a 7 mm sieve. The blended and sieved samples are then transferred to a 120 keg where they are allowed to settle over night.
In order to feed the reactors with fish slurry, dry matter content for feeding the reactors is 6-7%. To obtain this dry matter content, first a 14% dry matter content is prepared and then diluted 1:2 to attain the final slurry of 6-7% dry matter. Fish cuttings are broken down with a blender in 1:1 ratio (50% fish, 50% water). After further blending for homogenization, the cuttings are passed through a sieve of mesh size 3-5 mm. The sieved fish slurry is then transferred to a collecting bucket.
For measurement of pH level, conductivity and dry matter 4 samples are taken and analysed on a daily basis. Measurement of pH and conductivity are done with a small volumes of samples that are the returned to the mix. For measurement of dry solids content, a well-mixed sample is evaporated in a weighed dish and dried to constant weight in an oven at 103 to 105°C. The procedure and calculation of the dry matter content is described in D2.1. pH is adjusted by adding hydrochloric acid to elevate the pH level, and sodium hydroxide to lower the level as required.
Main achievements: The pre-processing has been necessary work that should continue as long as the AD scenarios have to be run, and the required digestate for the growth trials has been obtained. A good amount of data from the pre-processing has been also obtained during the duration of the AD operation; procedures for preprocessing of animal slurry and fish waste as well as the mixes of these has been established; knowledge on the quality of the substrate that enables optimum operation of the reactors with different mixes has been aquired; optimum values of parameters for smooth operation of the anaerobic digestion and high quality digestate for the growth trials have been maintained in the course of the Biffio trials.
3. AD TECHNOLOGY:
Based on the input from WP1 and the state-of-the-art a design of the current high rate bioreactor system will be fit to the need in terms of capacity, efficiency and product quality of biogas and remains.
For development of the AD, the results from WP1 have been evaluated and according to the results 4 test scenarios/system setups have been created. Based on the results it was decided to use the CSTR-reactor technology for the main anaerobic digestion reactor. Afterwards a test container with 4 CSTR-reactors (80l each) has been designed.
As part of the AD system, the control of the reactor and especially for the AD process a control system consisting of liquid and gas measurements have been develop. Temperature, Conductivity, pH and redox-potential will directly be measured within the reactor. The produced biogas will be analysed for Methan (CH4), Oxygen, Hydrogen sulphide and Hydrogen. The feed and the output will be analysed for it composition by lab-analysis. A test container containing 4 CSTR-reactors, control system, Biogas measurements and other necessary instruments and aggregates has been build according to the outcome of the design work. The container was transported to Liverpool and has been connected to the pre-treatment system.
A test matrix for the trials has been defined where different loads and mixtures will be tested. In order to archive repeat determination of results all scenarios will be done twice with different reactors but the same conditions (loads and mixture). The matrix that was created in Reporting Period 1 expanded due to the addition of fish cuttings as substrate from the aquaculture sector.
Test the prototype reactor. All scenarios from the test matrix and the replications of them have been successfully completed. During the test scenarios a view operational problems have been solved. All plant analysis have been executed and the received data has been evaluated.
4. SEPARATION AND USE OF DIGESTED MATTER:
The preliminary task of digestate post-processing is separation of the liquid and solid fractions.To start with, the task work was carried out with review literature regarding available methods for liquid-solid separation of sludge, advantages and drawbacks of the identified separation methods and their applicability to the digestate generated by the BiffiO process. Further to this, the literature review addressed the need (advantages) of separating the solid fraction from the liquid in the digestate as well as the value chain of the separated fractions.
From the identified methods, a short list was prepared based on relevant features for the BiFFiO best practice. These features include: Retention of nutrients in the separated fractions, Easiness to operate and maintain, Capacity/rate of dewatering, Footprint/need space, Reliability, Energy consumption, Possibility of automation, Suitability to different types of sludge, Instalment cost, Need of operator attention, Need of polymer and Secondary pollution.
Based on these considerations the following methods were included in the short list of potentially applicable methods for liquid –solid separation in the BiFFiO best practice. However, special consideration has been made in relation to technical complexity (need of qualified operators), economic implication for the end users and willingness of the market to pay for the solutions, as there was consensus in the consortium that cost benefit value should be given high priority in selection of the methods that suit the BiFFiO best practice in posttreatment of digestate. As a result, the short list of the short list included screw pressing, belt pressing, pressure filter press, drying
Centrifuges, electro-chemical flocculation/coagulation. Of these, screw pressing and electrochemical flocculation were taken forward as the most convenient conventional and emerging technologies respectively for the BiFFiO best practice. The functionality tests of these two methods should be used for selecting the best practice of liquid-solid separation in BiFFiO best practice. Manufacturing of a screw press unit was beyond the capacity of TI or the other beneficiaries. Therefore, a number of suppliers across Europe, especially in Germany and the UK, were contacted for manufacturing or leasing of a test unit. The smallest test unit that can be manufactured has a capacity 200L/h, while the Biffio plant can generate only 8 l/d. It has not been possible either to get any centrifuge unit with such small capacity. Therefore, the functionality tests were undertaken with a bench size electrostatic flocculation unit built in cooperation with a Welsh company (Power and Water). The Laboratory scale unit was installed at the University of Liverpool and subjected to tests using sludge from the BiFFiO anaerobic digester.
The electroflocculation process consists of electrolytic addition of metal ions to polluted water at an anode, and generation of gas microbubbles at a cathode in electrolysis cell. For the process to take place, electrodes are placed in water with an electric potential applied across the electrodes in order to cause electric current between them. The process operates based on the principle that the cations produced electrolytically from iron or aluminum anodes are responsible for the growth in the aggregation of contaminants from an aqueous medium. For running the process the test system built consists of a power supply unknit, a reaction chamber with electrodes at opposite corners of the chamber, a buffer tank, a peristaltic pump for circulation of the digestate to be processed and ultrasound cell for enhancing the hygienic quality of the separated fractions. Analysis of the dry mater content in the liquid fraction has been done after separation of the fractions using both iron and aluminium electrodes and at 2 and 5 amps. In all the samples analysed, the dry matter content is under 2,2% down from 10 -15 % in the feed digestate. This considerably high compared to what can be obtained with SOA methods. The level of separation could be potentially increased significantly by elevating the amperage to 15 – 20 amperes, but the test unit is not designed to such high power.
In the task of nutrient recovery, three main mechanisms of nutrient recovery were evaluated: i) Static accumulation of nutrients by absorption/fixation in three types of readily available and cost-effective media: activated carbon, zeolite and vermiculite by absorption or fixation from the liquid fraction of the digestate ii) use of a circulation system with an inline filter/media housing and iii) use of a circulation with a laboratory-scale electroflocculation and ultrasonic cell. The latter two mimicking in-line post-treatment system systems. We performed laboratory tests to determine the level of removal/recuperation of nutrients P, K and N. In both the static and circulation tests with minerals/activate carbon, we found that zeolite sequestered the most ammonia while activated carbon had little or no net effect. While in our experimental setup Vermiculite had less of an effect, the mass of vermiculite was 0.2 to 0.25 that of zeolite, therefore we would speculate that a similar mass of vermiculite may yield far higher removal rates than the zeolite. Electroflocculation shows potential for producing a concentrated fertilizer with both Ammonia Nitrogen and Phosphorus substantially decreased in solution. In contrast, potassium sequestration was not achieved. Further, there was substantial removal of the metals copper and zinc from solution. All of these result were achieved without extensive optimisation of the device.
Activities of the task related to storage, handling and use of the solid fraction are based primarily on literature study, discussions with experts in the field of digestate management and site visits. The outcome of the investigation is summarised as follows.
Storage: Usually, digestate is produced throughout the year and as a result there is a need to store until the appropriate time for application as a fertiliser during the growing season. The length of storage period will depend on several variables, including geographical area, soil type, winter rainfall, crop rotation and national regulations governing digestate applications. In many cases 6-9 month storage capacity is recommended, especially in areas designed as nitrate vulnerable zones (NVZ), and in some countries it is obligatory (e.g. Sweden, Denmark, Italy, Germany Austria). Unlike whole slurry especially from dairy cows, digestate does not usually form a crust during storage because the solid material that would have formed the crust is broken down during digestion to produce the biogas. When digestate is stored in open tanks, ammonia and methane gases are given off. These emissions can be reduced if the surface of the liquid is covered by a protective layer. The regulatory requirements of the IPPC (Integrated Pollution Prevention and Control) Directive and some national voluntary requirements of Biofertiliser Certification require that digestate stores be covered, but this may not be the case for on-farm storage of the finished product.
Location of the storage will be at the preference of the operator; either at the AD plant, or separate from the plant at the point of land application (if land is secured for spreading). Storage containers will need to be constructed to meet Health and Safety Executive (HSE) and planning regulations. In addition, some planning authorities require liquid storage facilities to have bunding around storage silos for spillage safety. Regulators may also require spillage and leakage detectors to be in place and monitored. When stored, operators should be aware that sediment in the digestate will settle out and will need to be stirred or agitated to ensure homogeneity before application or transporting. Due to the impermeable nature of roof structures and flexible covers, specialist design may be required to allow access for agitation equipment. With flexible covers, care needs to be taken to avoid mechanical damage during agitation.
Reviewed literature relevant to the task work shows that the solid fractions obtained with the separation methods presented in Task 4.1 consist of relatively high percentage of liquid. Unless directly applied as biofertiliser, it would require appropriate storage until the season for use as fertiliser or soil improver comes. If the solid fraction is to be used as a stable and marketable product, however, further processing in the form of composting and drying will be required. This is because solid fraction with high liquid content still contains biodegradable material that may stimulate microbial growth and odour emissions. The most common method of storage used is flexible polyethylene bags, but tanks covered with gas tight metallic plates or membrane can also be applied.
Transportation will be required when the land to which digestate is to be applied is not adjacent to the AD plant. Transporting digestate over long distances is expensive, and so availability of land should be considered in the early stages of planning an AD plant, particularly if the plant is located in an urban setting. If digestate disposal becomes necessary, for example liquids for treatment or solids to landfill, for even a proportion of output, it can have a huge impact on
business viability.
Solid digestate can be transported by truck and stored on fields under a rainproof cover prior to application. As a rule of thumb, dewatered cake from wet AD systems will require only 20% to 30% of the vehicle movements required for liquid digestate.
In relation to environmental and health impacts, the AD plant management, the landowner, the recycling team and the transport company should be regarded as equal partners in any digestate-to-land programme. All can be ultimately accountable to national and regional regulators and the acknowledgment of this fact is vital to the success of the operation.
Stabilisation by composting: During composting available microorgansms degrade and transform the organic material under aerobic conditions to compost. The compost is stabilised organic matter, containing humic substances. As biofertiliser the compost slowly releases nutrients and shows good performance as soil improver. However, as the solid fraction from digestate is wet and already partially degraded, the addition of bulking material such as woodchips is necessary for obtaining a stable composting process. Addition of bulking material helps to enrich the compost with air and enhancing and maintaining aerobic conditions. If a centralised composting site is available, it would be advantageous to do the composting at such centralised facility. Composting of the solid fraction generally increases the concentration of nutrients, but it may at the same time result in nitrogen loss.
Stabilisation by drying: When the solid fraction of digestate is subjected to drying, stabilisation of the product and reduction of the total mass as well as increase in the nutrient concentration is obtained. Drying can take place utislising the excess heat in a CHP unit. Different drying techniques can be applied including belt dryer, drum dryer, feed-and-turn dryer, and fluidised bed dryer. The most common technique for drying digestate is application of belt drying. Another common alternative is solar drying during the warm season. As the exhaust of the digestate dryers contains dust, ammonia, and other volatile substances such as volatile acids, exhaust gas cleaning systems have to be installed.
Use of solid fraction: The solid fraction of digestate can be used in different applications substituting industrially produced mineral fertilisers. Applications include use as bio-fertiliser for crops, soil conditioning, landscaping, horticulture, as home garden product and pellet fertiliser. Many of these applications require, however additional processing.
The three basic nutrients that are required in any fertiliser or soil conditioner are Nitrogen (for leaf and stem growth), Phosphorous (for root growth) and Potassium for flowers, fruit and health growth. Most commonly used feedstocks in AD such as animal manure, blood, fish and bone have however a low nitrogen value and therefore may have limited potential to productivity on their own. As a result, they must be combined with other, more nitrogen-rich materials (or mineral fertilisers). On the other hand if solid digestate is used consistently the results are increased organic matter in the soil, improved water filtration, reduced erosion and increased biological activity.
Solid digestate can be composted to act as a suitable soil improver in horticulture. However, digestate many not be the most appropriate alternative in certain horticulture areas. For production of fruit, vegetable, trees and shrub the nutritional values of digestate require supplementing to be sufficiently useful. It could also be sold bagged to home gardeners in the same way as any other compost, with good outcomes for the gardens and the environment.
There are a number of pellet products available with varying intended uses. These included slow release inorganic vegetable fertilisers, rose and shrub feeds, root boosters and multipurpose organic fertilisers. In order to compete with these products, however, digestate needs to be thermally dried and pelletised. From a nutritional perspective solid digestate has a higher nitrogen level than currently available products, although it typically has lower levels of phosphorous and potassium.
Fertilizer quality growth trials:
The nutrient content of the liquid digestate was strongly determined by the component mixture for anaerobic digestion. NPK were present in all digestates, but N was only present as ammonium nitrate and not detectable as nitrate nitrogen. The inclusion of marine aquaculture waste resulted in elevated levels of sodium. Ammonium nitrate is a more volatile source of nitrogen and may be less available for plant growth in the presence of sodium ions. The inclusion of cattle waste as a component of reactor mixtures elevated the presence of plant micronutrients.
The inclusion of fish cuttings in the mixture combinations in this study did not substantively alter the nutrient content of the resultant digestates.
Plant growth trials assessed the value of liquid digestate as a plant fertilizer for two species (Hordeum vulgare and Lolium perenne) during the vegetative stages of growth. In both plant species, responses to increased nitrogen applications as inorganic commercial fertilizer were observed with maximum yields of biomass in both species up to 100 Kg N / ha, affirming that the experimental growth trial system was adequate.
In H. vulgar, using both marine and freshwater based digestates as liquid fertilisers, no significant differences in yield responses were observed in either dry biomass or as total leaf length over an application range up to 100 Kg N / ha at the late vegetative stage (maximum tillering). Yield responses to the nutrient content of digestates derived from differing mixtures were not significant.
In L. perenne, there was no significant response to digestate nutrients derived from mixtures of freshwater based aquaculture waste when applied at 100 Kg N / ha, a rate which gave maximum yield when applied as inorganic nitrogen. Contrastingly, growth responses in relation to marine based aquaculture waste indicated suppression of growth when digestate was applied at rates giving over 50 Kg N / ha.
5. CONVERSION AND DISTRIBUTION OF BIOGAS:
In the work related to options for use and sale of biogas, the topics that have been addressed include the need and means of biogas storage, biogas distribution, use of upgraded biogas as biofuel, cleaning and upgrading of biogas and available technologies, technical and economic evaluation of upgrading methods and distribution of bio-methane. The outcomes are meant to be a component of the BiFFiO best practice to be implemented by the end users.
Biogas storage: In most cases, biogas is used in combined heat and power applications (CHP) that combust the biogas to generate electricity and heat for on-farm use. The electricity is typically produced directly from the biogas as it is created, although the biogas may be stored for later use when applications require variable power or when production is greater than consumption. Biogas that has been upgraded to biomethane by removing the H2S, moisture, and CO2 can be used as a vehicular fuel. Since production of such fuel typically exceeds immediate on-site demand, the biomethane must be stored for future use, usually either as compressed biomethane (CBM) or liquefied biomethane (LBM). Because most farms will produce more biomethane than they can use on-site, the excess biomethane must be transported to a location where it can be used or further distributed. As the principle for storage of biomethane and biogas are similar (even though the size, safety, pressure and material type various), storage of both products is addressed in the same section.
The two basic reasons for storage of biogas and bio-methane are: storage for later on-site usage and storage before and/or after transportation to off-site distribution points or systems. The least expensive and easiest to use storage systems for on-farm applications are low-pressure systems; these systems are commonly used for on-site, intermediate storage of biogas. The energy, safety, and scrubbing requirements of medium- and high-pressure storage systems make them costly and high-maintenance options for on-farm use. Such extra costs can be best justified for biomethane, which has a higher heat content and is therefore a more valuable fuel than biogas.
Distribution of biogas: Biogas can be transported using the same methods as for natural gas, either in piping systems or in gas cylinders. If the biogas is to be injected to existing natural gas grid, upgrading to natural gas quality is required. However, there is no requirement of upgrading if the biogas is to be transported by own piping system. Transport in cylinders takes place under pressure, i.e. as compressed biogas (CBG) or liquid biogas (LBG), CBG is suitable when transporting relatively small amount of gas over short distances and is the most commonly means of transporting biogas. The gas cylinders are mounted on a truck and are filled with the gas under a pressure of 300 bar.
For transporting biogas as LBG, the gas must be first cooled down to -162 °C. Then it can be transported by LNG trailer truck or a tanker. Whereas a CNG (compressed natural gas) truck can transport about 6000 Sm3, per trip, a trailer truck with liquefied gas can transport about 32000 Sm3 of gas in the same trip. For small and medium sized biogas plants, production and distribution of CBG is more cost effective. For plants that have capacity in the order of 60 GWh or higher, it can be worthwhile to consider distribution in the form of LBG. The advantage of transporting LBG also increases with increased transport distance.
Distribution of bio-methane: Biomethane can be distributed to its ultimate point of consumption by one of several options, depending on its point of origin:
• Distribution via dedicated biomethane pipelines
• Distribution via the natural gas pipeline
• Over-the road transport of CBG
• Over-the-road transport of LBG
Use of upgraded biogas: Raw biogas has a low energy density and can contain corrosive impurities that makes it not applicable to ordinary burners, engines and transporting systems. With further upgrading treatment involving removal of CO2 and other impurities, the gas can replace or supplement the non-renewable natural gas in most cases. After upgrading of the biogas to natural gas quality, the biogas (biomethane) can be used in vehicles that are adapted for running with gas, i.e. both cars, busses and ferries. Currently, there are 3 different types of vehicle engines that use gas as fuel:
• Dedicated gas engines (use only gas as fuel in the form of CBG or LBG)
• Bi-fuel engines, use can use two types of fuel (gasoline and gas) with gasoline as back up
• Dual –fuel engines, use two types of fuel simultaneously (diesel and gas). While driving outside cities with even speed, 80-90% of the fuel used is gas, while during city driving the percentage of gas consumption can be reduced to 75-80%. (IBID)
When biogas is used as a substitution to diesel and gasoline as fuel in vehicles, it contributes to lower emission of GHG. Moreover, there are other advantages including reduced emission of particles (nearly zero) and NOx in the exhaust gas from gas driven vehicles.
Cleaning and upgrading of biogas: As an outcome of the task work, cleaning of biogas is defined as the process in which impurities (undesired gas components) in the raw biogas are removed either to avoid corrosion in pipelines and other equipment, toxic substances such as H2S and risk of explosion, whereas upgrading of biogas is the process by which carbon dioxide is separated from the biogas to enhance the energy yield. Some upgrading methods both clean and upgrade the biogas, while other methods require a comprehensive pre-cleaning. The impurities in in this regard and require cleaning include water, H2S, oxygen, nitrogen and ammonia.
Biogas upgrading: Biogas to be injected to a natural gas grid, or used as biofuel has to be upgraded to a natural gas quality. The requirement of biogas quality for fuel purposes are not finite or absolute and there is no unified European quality specification set for bio-methane. There is however the Swedish standard of > 95 % methane content that is used in many countries. Moreover, the International Organization for Standardization has made a standard called “Natural gas for use as compressed fuel for vehicles – Part 1: Designation of the quality”. This standard is also used for upgraded biogas and regulates methane content to a minimum of 96 Vol-% (Deublein & Steinhauser 2008). In addition, it sets limitations for the contents of hydrogen sulphide, total sulphur, carbon dioxide, oxygen, hydrocarbons and water.
For addressing the need of cleaning and upgrading biogas, a number of methods have been developed. The most developed and widely used ones include: Pressure swing adsorption, Membrane separation, Water scrubbing, Organic physical scrubbing and Organic chemical (Amine) scrubbing. The principle of operation of these methods is presented in Deliverable 5.1 Part A, Section 5.8.
In the task work, technical and economic evaluation of the upgrading methods has been undertaken based on literature review. The outcome of the evaluation is presented in Deliverable 5.1 Section 5.9 and 5.10.
Activity and Results of case studies: The following data were collected for modelling AD plant feasibility by questionnaire, telephone canvassing and visits to SSPO and BTA members.
Location of farm, the volume of waste produced, the variability of the volume of waste (seasonal? Max, min per week), nature of waste: slurries, processing waste, cuttings, mort; current storage capacity for waste(s); current disposal pathway and cost of disposal , possible uses of slurry/digestate. Potential local uses for heat on site or close by. Are there any space restrictions for storage and installation of plant or other local restrictions, considerations or barriers?
Further data was compiled or estimated from our results:
• Physical/chemical data of the slurry
• Total solids/Volatile Solids of waste
• Bio(gas)/(methane) potential
A spreadsheet was constructed for each farm and the closest scenario to the nature or mix of waste streams available was used to estimate gas outputs to give volume (or equivalent) of methane gas produced, raw/total power, an estimate of parasitic load, the maximum (exportable) electrical power and thermal power (using all of this raw energy), applicable FIT and reactor size, maximum exportable electricity (100% of energy converted to electricity, assuming 30% generation efficiency) and thermal (100% of energy converted to heat), assuming a 65% boiler efficiency. For animal products, the pasteurization cost was calculated as the total cost of increasing temperature to 70°C from ambient but no account was made for maintaining that temperature for one hour.
UK Feed in Tariffs were used for “cash” calculation, however the most efficient use of electricity was assumed to be use on site, thus reducing cost of buying in electricity. Data were collected for over 10 farms and a selection of four, representing the sector were developed as case studies.
6. BEST PRACTICE
The results from the scientific and technical work in WP1-WP5 of the project have been assimilated into a best practice guide or reference document. The intention is to develop an output to be used by the end users in management of aquaculture and agriculture waste in a sustainable manner. The guide is prepared as Deliverable 6.1 that also includes the material used for training of the trainers..
For economic evaluation the BiFFiO best praactice, an assessment has been made regarding the policies in the countries that are represented by the SMEs towards both biogas production and use of digestate generated by by anerobic digestion in order to define the boundary conditions for the economic evaluation. Further to this, the task work has looked into existing divers and barriers for access to feedstock, production and use of biogas as well as use of generated residue from anaerobic digestion. As a tool for use in the economic evaluation a model has been developed for calculating the economic benefits of using the BiFFiO best practice based on the revenue and cost factors.
There are diverse policies in the different countries even though the sum of the drivers and barriers in Germany and Norway as well as the other Scandinavian countries more or less similar. There is also price difference of energy between the different countries. Therefore the model has used average specific prices, for example transport and electricity. There is also big difference in development of grid for distribution of gas, for example between the UK and Norway as the main source of energy production in Norway is hydropower. However, upgrading and sale of biomethane is not considered in the economic evaluation as the consortium considered this element of biogas production slightly remote for the SME-AGs. Moreover, studies made on the economic potential of upgraded biogas in Sweden has shown that there is no profit unless there is sufficient government incentive.
Risk Assessment and Contingency Management:
This task has included the close monitoring of the progress in the different RTD WPs in order to ensure coordination and integration of the technical activities and solutions in the production process from pre-treatment to use of bioenergy and digested matter. Special focus was being given on the interface between the different WPs, especially the interface between WP2 Pre-treatment, WP3 AD technology and WP4 Post treatment – Separation and handling of digested matter. Further close focus were be given for WP5 and the feasibility study of the conversion and use of biogas. TI, as the task leader and coordinator of the BiFFiO project, has closely monitored the progress in these WPs. The monitoring was carried out by having frequent RTD meetings and planning for the best integration between WP 2, 3 and 4. As an example, there have been several discussions and planning for post-treatment process, even though the WP 4 has not started formally. Contingency management for WP - 2, 3 and 4 was conducted to ensure good interface between them.
The development of technology and best practice in WP2, WP3 and WP4 have undergone risk assessment by close monitoring of progress in the different work packages and their inter-relationship with the entire project. Likelihood of failures within work packages and tasks have indicated and evaluated and the likely tolerance band for under-delivery assessed. Corrective actions were initiated if required reassessing the cumulative effect of the changes on the predicted tolerance band of the major element deliverable and confirm that this is acceptable in relation to the overall project objectives. A corrective action was to continually running the test for pre-treatment and integrates it with the WP3 trial. There may be some re-iteration for some of the tasks with changes to their content that are likely to produce an improved deliverable closer to the quantified target. The improved deliverable will then be re-integrated into the milestone assessment.
Contingency planning to ensure that the operational goals are met was considered specifically at work package level. WP2: in case equipment fails to meet the quality or performance criteria, prepare SoA alternatives for feed production suitable for testing of bioreactor performance in WP3. WP3: In case own pilot reactor equipment fail to meet the quality or performance criteria, deploy a lab-scale or similar test alternative for testing of bioreactor performance, and provide biogas and sludge for post-treatment use in WP4. WP4: In case separation or novel absorption technology fails to work properly, design other laboratory tests to document the quality and valorisation potential of digested matter.
Potential Impact:
The BIFFIO project will contribute towards compliance with EU directives, policies and acts such as Nitrate Directive (91/676/EEC, Environmental Protection Act (2000/86), Government Decree No 931/2000), Water Framework Directive (2000), and Groundwater Directive (2006), the common agricultural policy, Council Directive 86/278/EEC of 12 June 1986). Environmental impact can, by using the BiFFiO technology, be reduced in terms of reduction in GHG emission, nutrient run-off and unwanted odour and improvement of sanitation and hygiene. The aquaculture and agriculture industries can use BIFFIO as an inventive way to take economical advantage of the potential use of their waste products and in turn reducing their emissions, runoffs and waste handling costs.
The BiFFiO project will provide technological solutions and best practices useful to an extensive number of European SMEs within the agriculture, aquaculture and bioenergy sector. Both the aquaculture and agriculture industries face regulatory and social requirements for the waste produced in addition to the fact that the aquaculture industry has an energy need which can be assisted by production of biogas from the waste.
A possible positive return on investment for the farms will encourage use of the new best practice and purchase and use of the BiFFiO reactor technology. An estimated 3 years pay backs seems attractive to farmers. A lower cost level like this will make it considerably easier for the aquaculture and agriculture industries to use biogas production as a method to handle their waste issues.
The BiFFiO project has as one objective to recover nutrients during the process. The farmers will hence be able to reduce their need to purchase fertilizers and reduce their costs. In addition, any excess nutrients can be sold on the market, creating an income. There is a growing acceptance that an increased amount of nutrients via manure processing must be exported from regions with surplus nutrients to regions low in nutrients.
Both in Europe and internationally, animal manure is a significant contributor to the GHG emission in the form of methane and nitrous oxide. Application of the BiFFiO best practice would contribute to mitigation of green house emission by utilising the manure as source of renewable energy. Additional benefit is retaining the nitrogen in the manure as a nutrient rather than its loss when converted to ammonia and nitrous oxide. An indirect societal and environmental benefit is substitution of fossil based energy by energy based on renewable source. Further to this, utilisation of fish waste including cuttings contributes to supplementing the depletion of phosphorous that is becoming a scarce commodity.
Use the biogas as upgraded biofuel substitutes fossil based fuel contributes to reduced GHG and NOX. Use organic fertiliser generated by the BiFFiO best practice has also indirect value as it reduces the need for production of inorganic fertiliser and associated emission of GHG.
List of Websites:
Website address: www.biffio.com.
Contact details: Mr. Mezmur Shiferaw, Email: mezmur.shiferaw@ti.no. Phone: +4795818829.
Mr. Morten Berntsen, Email: morten.berntsen@ti.no. Phone: +4798290366