Final Report Summary - MICROFUEL (Mobile microwave pyrolysis plant turns biomass into fuel locally)
Executive summary:
This project will help to make the European forestry sector more profitable. We have developed technologies for making use of forestry waste - branches, twigs, bark leaves, sawdust, stumps etc. At present, this is left to rot in the forest, producing methane (a greenhouse gas) and producing no income for the forestry owners. We have developed technologies to make use of this untapped resource, so Europe's forestry owners can augment their income and increase their competitiveness globally.
The technological aim of the project was to develop a pre-commercial prototype microwave pyrolysis plant capable of very rapid (less than 1 second) pyrolysis of forest residue. The rapid pyrolysis produces a bio-oil that can be used directly as a substitute for fossil fuels in boilers, stationary diesel engines and gas turbines.
The project consortium was composed of 4 forestry trade associations (AGs), covering the interests on European, Spanish, Norwegian and Estonian forestry owners. A further AG represented the interests of Spanish heating engineers. 4 small and medium-sized enterprises (SMEs), from France (2), Norway and Italy represented a supply chain of companies to exploit the technology and build plants for the rapid pyrolysis of forestry waste. Finally, 3 research performers (United Kingdom, Norway and Italy) built, integrated and tested a prototype microwave (m/w) pyrolysis unit for wood waste.
The overall technical goal of the project is to build a scalable prototype plant that can turn up to 230 kg / h of low value forest floor residue that is currently unused, into char, as well as a valuable bio-oil that can be used as a carbon dioxide (CO2)-neutral fossil fuel replacement. There were many technical delays in the project, so a working prototype was produced only at the end. We were not able to produce bio-oil and biochar continuously from wood chips. However, we have been able to design and build an m/w pyrolysis plant which can produce both bio-oil and biochar from wood chips on a batch basis - so the overall goals were partially met:
- A flammable bio-oil was produced, along with very light and (most likely) activated biochar. However the overall pyrolysis process is still under development. The bio-oil produced shows a high enough calorific value to be able to burn when heated.
- At the end of the technology development phase of this project, the technology is still in need of further refinement, if it is to be used in continuous operation, rather than batch mode. As continuous operation was not possible, a true capacity figure is difficult to estimate. However, tests so far indicate that a throughput of 400-500 kg / h is possible with the current design and configuration. The results presented show that it is likely that a full scale continuous mode plant will have a capacity of 2 000 kg / h, using 400 kW m/w power.
- The foot print of the system is small enough to fit into two 20' International Organisation for Standardisation (ISO) shipping containers. We have thus produced a working prototype, with the potential for good transportability, capable of remote operations deep within Europe's forests.
Technical delays meant that at the close of the project, not all of the objectives were met, due to several serious integration delays. However, all subunits have been manufactured and tested. There were notable issues with some subunits:
- cracking of ceramic plates in the reactor;
- the systems for feeding in woodchip feedstock and extracting char did not meet the specifications set out in the request for quotation. This meant that we were unable to operate the prototype in continuous mode;
- the monitoring and control system was not fully integrated or tested;
- a liquid-to-solid yield ratio was estimated to about 50:50 (by weight), but no validation or process repeatability data can be given at this stage.
We have made extensive recommendations for how this basic prototype can be refined in further trials.
Project context and objectives:
Socioeconomic background
Around 15 million private forest owners own about 60 % of the forest land in the European Union (EU). Privately-owned forests have an average size of 13 ha, but the majority of them are less than 3 ha in size. The forest owners supply the raw material for the forest based industries with the help of 492 000 persons employed in forestry. In economic terms, the EU has become the second largest industrial round wood producer as well as the world's biggest sawn wood and paper manufacturer. Forestry and forest-based and related industries employ about 3.4 million people. Already before the latest expansion of the EU, the production value of the forest-based industries (EU-15) was almost EUR 300 billion, corresponding to 10 % of the total for all manufacturing. The forest sector is very heterogeneous and is characterised by global, regional and local companies, hundreds of thousands of small and medium-sized enterprises and some large multinationals. Wood and wood products manufacturers are dominated by micro-companies with a total of 160 000 companies employing 8 persons on average.
The economic viability of European forest management is threatened by the outlook of increasing labour cost and stable or even falling prices for forest products, partly due to the availability of extremely productive and cheap sources of wood fibre outside Europe. The capacity utilisation is low and only slightly over 60 % of the annual forest growth is being harvested.
The forestry sub-sector harvests forests and supplies the paper industry, saw mills etc. Forestry suffers from severe job losses due to continued increases in mechanisation without a corresponding increase in production. At the start of this project, we estimated that 70 000 jobs would be lost in central and eastern European countries and 40 000 jobs lost in western Europe between 2000 and 2010.
According to the objectives set by the European Commission (EC) in the 'Forest' action plan the forest sector should aim to fulfil the forest-related goals of the Biomass Action Plan. According to the redefined 'Biomass' action plan of 2005 it is estimated that in fully exploiting its potential, the EU-25 could consume approximately 185 Mtoe (Mega tonnes oil equivalent) by the end of the year 2010. The measures outlined in the plan will bring biomass consumption up to around 150 Mtoe in 2010. However estimates indicate that at the current growth there will be an EU short fall of 46 Mtoe. There are several additional sources of bio-mass that may be used as feed-stock, but forestry residues alone can cover one third of this shortfall. The environmentally-compatible bio energy potential from forestry residues is estimated to be around 15 Mtoe in 2010, increasing to 16.3 Mtoe in 2030.
The MICROFUEL concept
Our concept is to increase biomass energy use in forests by developing a mobile, very rapid (< 1 s) pyrolysis plant that can process forest floor residue and wood waste on location. The pyrolysis products are bio-oil and biochar with a much higher energy density than the biomass input. Wood residue of little or no commercial value at present will be turned into fossil fuel replacements and/or high value organic chemicals. The processing creates high value products and saves transportation costs as the bio-oil occupies only a third of the volume of wood.
Bio-oil from very rapid pyrolysis can be used directly as a substitute for fossil fuels used in boilers after modifying the transport system and fuel nozzles. It can also be used in stationary diesel engines and gas turbines for power generation. Processes to upgrade the bio-oil to an automotive diesel substitute are under development. Bio-oil produced by pyrolysis has been estimated to be the most inexpensive liquid fuel based on biomass.
Turning wood into pyrolysis oil in local plants is a method of producing a fossil fuel replacement of high value at a low cost as the plant is powered with wood fuel and the pyrolysis oil is compressed to one third of the volume of the original wood or almost half of wood pellets. Transportation cost is limiting the use of firewood. Pellets are a more compact fuel, but still the practical distance between consumer and supplier is limited to 200 km. Liquid bio-fuels have a higher commercial value as they are easier to adapt to applications were liquid fossil fuels are currently used.
Technological objective
Our technical objective was to develop a pre-commercial prototype microwave pyrolysis plant capable of very rapid, < 1 s, pyrolysis of up to 230 kg / h of forest residue. Furthermore, we intend to design a plant of 10 times this scale capable of processing up to 2 300 kg / h integrated with a 1.3 MW diesel generator running on bio-oil for a process output of over 70 % by weight bio-oil. This will enable the AG members, the forest owners to either process them-selves or sell to other processors of the forest floor residue that is currently unused, into valuable bio-oil and char as a CO2-neutral fossil fuel replacement. It is desirable to maximise the pyrolysis oil and minimise char and gas as the oil has the highest value. 230 kg / hr is selected because the plant needs to be of a certain minimum size to be scalable to the desired capacity of 2 300 kg / h (which again is a reasonable trade-off between mobile size and operator cost). We can eliminate very small (i.e. 20 kg / h) systems because the materials handling and feeding will not be scalable at these throughputs.
Our scientific objectives were to:
- investigate the dielectric (microwave heating) properties of the feedstock with different samples of wood and varying moisture content, and to investigate the dielectric properties of intermediates and pyrolysis products formed during the process and under process conditions (different densities; enhanced temperatures etc);
- investigate the pyrolysis product quality and microwave power density requirements for treatment times down to less than 1 s;
- build a three-dimensional simulation model in order to visualise the interactions between the electromagnetic field and the process materials in a range of conceptual microwave cavities suitable for continuous processing;
- understand how the microwave pyrolysis products vary as a function of the raw material parameters (moisture content, feedstock size and type) and process conditions (power and residence time).
Our technical objectives were to:
- design and build a reaction chamber with feeding (microwave cavity) which gives an electric field distribution which can heat the feedstock evenly in < 1 s to 500 degrees of Celsius to minimise char formation;
- design and build a solids handling system with controlled drying and preheating capable of more than 230 kg / h continuous operation, which can be integrated with the microwave cavity and vapour recovery systems;
- design and build an automated control system with multipoint temperature measurements with time constant < 50 ms and feed rate control capable of closed loop control of the process to within +/- 200 degrees of Celsius to maximise liquid yields and to prevent carbonisation and gasification;
- design and build a vapour condensation system limiting the residence time in the chamber and quenching the vapour to limit gas formation and maximise liquid yield with a capacity of 120 l / h;
- design and build an inert gas system utilising recycled pyrolysis gas to limit inert gas consumption to an average of less than < 30 l / h or less than 3 bottles (80 l / 300 bar) of N2 per month in continuous operation.
Our integration goals were to:
- design and construct a scalable 230 kg / h continuous prototype reactor for < 1 s pyrolysis and > 70 % efficiency to prove the concept;
- achieve repeatable product quality < 5 % variation in distribution between oil/char/gas from batch to batch;
- achieve a process able to repeatable produce pyrolysis liquid levels > 70 % of wood weight;
- achieve scalability to a reactor chamber design for 2 300 kg / h and max. 1 000 kW microwave power for a plant with a manufacturing cost in serial production lower than EUR 1 750 000 including parts and fit in two 40'' ISO containers.
Our other objectives were:
- Innovation: To protect intellectual property rights (IPRs) produced and patent and exploit the technologies, to establish a supply chain to exploit the technology and to develop a future funding and investment plan.
- Dissemination: To disseminate the know-how produced within the consortium and (if appropriate) outside it.
Project results:
At the start of the project, we characterised the dielectric properties of two forestry waste samples at two industrially-allocated frequencies and at temperatures from 20-800 degrees of Celsius. Two measurement techniques were used, based upon a cavity perturbation method to give accurate dielectric property readings at all temperatures. The dielectric constant and dielectric loss factor both vary significantly with temperature at both frequencies, and the behaviour is explained based on the water content and the degree of graphitisation due to combustion.
The findings of D1.1 indicate that all forest waste materials absorb microwave energy strongly at temperatures > 600 degrees of Celsius, once the material pyrolyses. When this occurs, a phenomenon known as 'thermal runaway' will take place, where temperatures well in excess of 1 000 degrees of Celsius can be achieved in seconds. These temperatures are sufficient to melt quartz reactor vessels, so a dedicated microwave heating system is required for the batch microwave pyrolysis experiments.
Thus microwave pyrolysis of forest wastes can be achieved without the use of microwave-absorbing additives. High-power densities and short residence times are required to promote bio-oil yields and maximise the efficiency of the process.
All materials handling technologies were evaluated and four continuous processing concepts were shortlisted. Electric field simulations showed that a belt conveyor is able to achieve a power density which is very high and evenly distributed and low residence times, but only for feedstocks that are very closely-controlled. Other systems have disadvantages in the power density distribution and residence time but are able to process a wider range of materials.
In work package (WP) 2, we confirmed that we were able to design a microwave pyrolysis plant with feeding system for continuous processing of forest residues. WP3 concentrated on the MICROFUEL monitoring system - the design and building of an automated control system with different sensors and multipoint temperature measurements with time constant < 50 ms and feed rate control capable of closed loop control of the process to within +/- 200 degrees of Celsius to maximise liquid yields and to prevent carbonisation and gasification.
The monitoring system we developed is a PLC system, with the process picture and process values presented on a computer screen. The PLC and the computer form the process control system (PCS). The system also interacts with the motor control system (MCS), which controls all the power circuits (motors, heaters, magnetrons etc).
The main individual loops, indications and alarms developed for the MICROFUEL monitoring system related to the MICROFUEL process functioning and systems are:
- raw material infeed hopper level system;
- screw conveyor drive;
- oxygen control;
- reactor temperature indication and control;
- pressure control and monitoring;
- turntable speed control;
- carbon cooler temp. control;
- recirculation gas temperature;
- process vapour pressure control;
- column fluid level control;
- settling tank level control;
- scrubber level control;
- system pressure control;
- gas emergency shutdown (ESD) relieve control;
- flare knock-out drum condensate level;
- flare gas flow indication;
- flare burner temperature;
- inert gas pressure;
- plant air pressure;
- cooling medium instrumentation.
The objective of WP4 was to design and build a vapour condensation system limiting the residence time in the chamber and quenching the vapour to limit gas formation and maximise liquid yield with a capacity of 120 litres per hour. Furthermore, to design and build an inert gas system utilising recycled pyrolysis gas to limit inert gas consumption to an average of less than 30 litres per hour or less than 3 bottles of N2 per month in continuous operation.
D4.1 described the prototype, designs and tests of MICROFUEL's gas and vapour system. The results confirmed that the initial idea was feasible and possible with different approaches. Therefore, the simulation and design are fulfilled, but the installation was not been finalised, due to delay in manufacturing the rest of the prototype - in the event, a much simpler condenser was used to condense the gases evaporated from the pyrolysis of wood chips.
In WP5, we integrated the entire MICROFUEL system. There were many technical delays in the project, so a working prototype was produced only at the end. We were not able to produce bio-oil and biochar continuously from wood chips. However, we have been able to design and build an m/w pyrolysis plant which can produce both bio-oil and biochar from wood chips on a batch basis - so the overall goals were partially met:
- A flammable bio-oil was produced, along with very light and (most likely) activated biochar. However the overall pyrolysis process was still under development at the project close.
- The bio-oil produced shows a high enough calorific value to be able to burn when heated.
- At the end of the technology development phase of this project, the technology is still in need of further refinement, if it is to be used in continuous operation, rather than batch mode.
- As continuous operation was not possible, a true capacity figure is difficult to estimate. However, tests so far indicate that a throughput of 400-500 kg / h is possible with the current design and configuration. The results presented show that it is likely that a full scale continuous mode plant will have a capacity of 2 000 kg / h, using 400 kW m/w power.
- The foot print of the system is small enough to fit into two 20' ISO shipping containers. We have thus produced a working prototype, with the potential for good transportability, capable of remote operations deep within Europe's forests.
Technical delays meant that at the close of the project, not all of the objectives were met, due to several serious integration delays. However, all subunits have been manufactured and tested. There were notable issues with some subunits:
- Cracking of ceramic plates in the reactor.
- The systems for feeding in woodchip feedstock and extracting char did not meet the specifications set out in the request for quotation. This meant that we were unable to operate the prototype in continuous mode.
- The monitoring and control system was not fully integrated or tested.
- A liquid-to-solid yield ratio was estimated to about 50:50 (by weight), but no validation or process repeatability data can be given at this stage.
We have made extensive recommendations for how this basic prototype can be refined in further trials.
We were able to produce several samples of bio-oil from the flash pyrolysis of wood chips.
Three samples of this bio-oil have been analysed to determine their contents and properties.
The analysis determined that the samples:
- would ignite in simple combustion tests;
- had combustion temperatures of between 400-520 degrees of Celsius, confirming suitability as a fuel;
- contained a range of volatile compounds from wood, including alkyl groups, aromatics, anilines, aromatic esters, ketones, amide and aromatic aldehydes; and
- contained further semi-volatile compounds, such as cresols and vanillin, which could be useful platform or speciality chemicals in any large-scale process.
Potential impact:
Cost-benefit analysis:
In terms of cost benefit analysis, with modifications, the estimated price tag for a full-scale MICROFUEL system (using 4 microwave generators, rather than the single unit demonstrated in this project) would be EUR 1 300 000 per unit. Selling price would be around EUR 2 200 000 per unit.
In economic terms, the total system (MICROFUEL unit, plus pre-drying equipment, gas-powered generator and civil engineering costs) would use wood waste as a fuel source to produce both bio-oil and biochar. Operating at full capacity, estimated payback period would be a respectable 3.3 years. Such a plant would be capable of producing 8 700 tons of bio-oil per annum - at May 2012 prices; this would have a value of EUR 3.2 million. As a by-product, a further 6 000 tons of biochar could be sold to the ferrosilicon industry. (Ferrosilicon is produced by the reduction silica with carbon in the presence of scrap iron). To the Norwegian ferrosilicon sector, the biochar would have a value of EUR 1.8 million.
In terms of CO2 balance, the bio-oil produced by such a plant represents a potential reduction of 16,600 tons of CO2 emissions per year. If the bio-gas is used fully, this would represent a further 25,509 tons of equivalent emissions reduction. If the biochar was used for sequestration, rather than for industrial uses, then the CO2 sink potential represents further 18 412 tons in reduced emissions.
Dissemination:
Limited information on the project is available on the public page of the project's website. Most partners have publicised the project at annual general meetings, in press releases or at conference and these activities are summarised here. One peer-reviewed paper was published.
Internal dissemination activities:
Throughout the project, partners have used the projects website www.micro-fuel.eu for internal dissemination of meeting notes, technical discussions, design drawings and the formal deliverable reports (both in draft and in final versions). D7.1 (Project website) summarises these activities. The website has a public page, where basic information on the project is given. There is also a contact listed for people requesting more information.
The website has received considerable interest and one enquiry. (For example, on 20 July 2012, the project was approached by a consultant in Brazil who wished to represent the project and the consortium in that region. On 21 August 2012, a similar request was received from the Philippines. In both cases, the interest was in using the technology for pyrolysis of crop waste biomass - bagasse and rice husks / straw).
Partners have met regularly during the project to discuss progress. At their final meeting (M41, in Notodden in Norway), the researcher team presented the final working prototype to the consortium.
External dissemination activities
The MICROFUEL team have made several demonstrations of their technology in open days or to visitors at the Notodden pilot plan. As an example, on 6 March 2012, the team received a visit Norway's Environment Minister, Mr Erik Solheim.
Basic information on the technical success of the project was issues as a press research on 23 May 2012. This included some basic pictures of the pilot plan and a description of the relevance of the project to the forestry industry. A link to the press release was inserted into the project web sites home page. Each partner has made use of the press release in different ways.
Partner activities
- Nor-Tek: On 25 June 2012, details of the project we published in English in Pera News; Pera is Nor-Tek's parent company). Pera News has a weekly circulation of 9 631 (August 2012 figures). In July, Pera drafted a case study on the project, based on information outlined in the website. The case study highlights the benefits of a consortium of different European organisations developing technology through Framework.
- CGS: In June 2012, CGS mentioned the project on their web site. University of Nottingham: The team presented a paper at the AMPERE 2011 conference in Toulouse. This presentation covered some aspects of the MICROFUEL project. In 2010, the published a paper in the journal Industrial & Engineering Chemistry Research. This is a peer-reviewed journal has an impact factor of 2 237 and 34 547 annual citations in 2011.
- EPFU: Cited the project on their home page. Staff from EPFU have presented details of the project to 829 Estonian forestry owners at events such as the general meeting, forest owners' reunions and forest tent events. These tent events take place within Estonian forests and involve local communities.
- NFOF: Reported on the start of the project in a news item on their website. The project has also been highlighted in two articles in NFOFs in-house magazine (Skogeiern), which has a circulation of 40 000. This newsletter is read widely throughout the Norwegian forestry industry. In June 2012, NFOF covered the project at their annual conference of forestry owners in Norway ('Skog og Tre').
- COSE: Held some specialist dissemination activities within the Spanish forestry sector.
- Thermya: Reported no dissemination activities.
- Pymetal: Reported no external dissemination activities.
- CEPF: Arranged some specialist dissemination activities for European forestry managers.
- GSD: Reported no external dissemination activities.
- Sairem: Reported no external dissemination activities.
- SBC: Covered the project on their web site.
List of websites: http://www.micro-fuel.eu
This project will help to make the European forestry sector more profitable. We have developed technologies for making use of forestry waste - branches, twigs, bark leaves, sawdust, stumps etc. At present, this is left to rot in the forest, producing methane (a greenhouse gas) and producing no income for the forestry owners. We have developed technologies to make use of this untapped resource, so Europe's forestry owners can augment their income and increase their competitiveness globally.
The technological aim of the project was to develop a pre-commercial prototype microwave pyrolysis plant capable of very rapid (less than 1 second) pyrolysis of forest residue. The rapid pyrolysis produces a bio-oil that can be used directly as a substitute for fossil fuels in boilers, stationary diesel engines and gas turbines.
The project consortium was composed of 4 forestry trade associations (AGs), covering the interests on European, Spanish, Norwegian and Estonian forestry owners. A further AG represented the interests of Spanish heating engineers. 4 small and medium-sized enterprises (SMEs), from France (2), Norway and Italy represented a supply chain of companies to exploit the technology and build plants for the rapid pyrolysis of forestry waste. Finally, 3 research performers (United Kingdom, Norway and Italy) built, integrated and tested a prototype microwave (m/w) pyrolysis unit for wood waste.
The overall technical goal of the project is to build a scalable prototype plant that can turn up to 230 kg / h of low value forest floor residue that is currently unused, into char, as well as a valuable bio-oil that can be used as a carbon dioxide (CO2)-neutral fossil fuel replacement. There were many technical delays in the project, so a working prototype was produced only at the end. We were not able to produce bio-oil and biochar continuously from wood chips. However, we have been able to design and build an m/w pyrolysis plant which can produce both bio-oil and biochar from wood chips on a batch basis - so the overall goals were partially met:
- A flammable bio-oil was produced, along with very light and (most likely) activated biochar. However the overall pyrolysis process is still under development. The bio-oil produced shows a high enough calorific value to be able to burn when heated.
- At the end of the technology development phase of this project, the technology is still in need of further refinement, if it is to be used in continuous operation, rather than batch mode. As continuous operation was not possible, a true capacity figure is difficult to estimate. However, tests so far indicate that a throughput of 400-500 kg / h is possible with the current design and configuration. The results presented show that it is likely that a full scale continuous mode plant will have a capacity of 2 000 kg / h, using 400 kW m/w power.
- The foot print of the system is small enough to fit into two 20' International Organisation for Standardisation (ISO) shipping containers. We have thus produced a working prototype, with the potential for good transportability, capable of remote operations deep within Europe's forests.
Technical delays meant that at the close of the project, not all of the objectives were met, due to several serious integration delays. However, all subunits have been manufactured and tested. There were notable issues with some subunits:
- cracking of ceramic plates in the reactor;
- the systems for feeding in woodchip feedstock and extracting char did not meet the specifications set out in the request for quotation. This meant that we were unable to operate the prototype in continuous mode;
- the monitoring and control system was not fully integrated or tested;
- a liquid-to-solid yield ratio was estimated to about 50:50 (by weight), but no validation or process repeatability data can be given at this stage.
We have made extensive recommendations for how this basic prototype can be refined in further trials.
Project context and objectives:
Socioeconomic background
Around 15 million private forest owners own about 60 % of the forest land in the European Union (EU). Privately-owned forests have an average size of 13 ha, but the majority of them are less than 3 ha in size. The forest owners supply the raw material for the forest based industries with the help of 492 000 persons employed in forestry. In economic terms, the EU has become the second largest industrial round wood producer as well as the world's biggest sawn wood and paper manufacturer. Forestry and forest-based and related industries employ about 3.4 million people. Already before the latest expansion of the EU, the production value of the forest-based industries (EU-15) was almost EUR 300 billion, corresponding to 10 % of the total for all manufacturing. The forest sector is very heterogeneous and is characterised by global, regional and local companies, hundreds of thousands of small and medium-sized enterprises and some large multinationals. Wood and wood products manufacturers are dominated by micro-companies with a total of 160 000 companies employing 8 persons on average.
The economic viability of European forest management is threatened by the outlook of increasing labour cost and stable or even falling prices for forest products, partly due to the availability of extremely productive and cheap sources of wood fibre outside Europe. The capacity utilisation is low and only slightly over 60 % of the annual forest growth is being harvested.
The forestry sub-sector harvests forests and supplies the paper industry, saw mills etc. Forestry suffers from severe job losses due to continued increases in mechanisation without a corresponding increase in production. At the start of this project, we estimated that 70 000 jobs would be lost in central and eastern European countries and 40 000 jobs lost in western Europe between 2000 and 2010.
According to the objectives set by the European Commission (EC) in the 'Forest' action plan the forest sector should aim to fulfil the forest-related goals of the Biomass Action Plan. According to the redefined 'Biomass' action plan of 2005 it is estimated that in fully exploiting its potential, the EU-25 could consume approximately 185 Mtoe (Mega tonnes oil equivalent) by the end of the year 2010. The measures outlined in the plan will bring biomass consumption up to around 150 Mtoe in 2010. However estimates indicate that at the current growth there will be an EU short fall of 46 Mtoe. There are several additional sources of bio-mass that may be used as feed-stock, but forestry residues alone can cover one third of this shortfall. The environmentally-compatible bio energy potential from forestry residues is estimated to be around 15 Mtoe in 2010, increasing to 16.3 Mtoe in 2030.
The MICROFUEL concept
Our concept is to increase biomass energy use in forests by developing a mobile, very rapid (< 1 s) pyrolysis plant that can process forest floor residue and wood waste on location. The pyrolysis products are bio-oil and biochar with a much higher energy density than the biomass input. Wood residue of little or no commercial value at present will be turned into fossil fuel replacements and/or high value organic chemicals. The processing creates high value products and saves transportation costs as the bio-oil occupies only a third of the volume of wood.
Bio-oil from very rapid pyrolysis can be used directly as a substitute for fossil fuels used in boilers after modifying the transport system and fuel nozzles. It can also be used in stationary diesel engines and gas turbines for power generation. Processes to upgrade the bio-oil to an automotive diesel substitute are under development. Bio-oil produced by pyrolysis has been estimated to be the most inexpensive liquid fuel based on biomass.
Turning wood into pyrolysis oil in local plants is a method of producing a fossil fuel replacement of high value at a low cost as the plant is powered with wood fuel and the pyrolysis oil is compressed to one third of the volume of the original wood or almost half of wood pellets. Transportation cost is limiting the use of firewood. Pellets are a more compact fuel, but still the practical distance between consumer and supplier is limited to 200 km. Liquid bio-fuels have a higher commercial value as they are easier to adapt to applications were liquid fossil fuels are currently used.
Technological objective
Our technical objective was to develop a pre-commercial prototype microwave pyrolysis plant capable of very rapid, < 1 s, pyrolysis of up to 230 kg / h of forest residue. Furthermore, we intend to design a plant of 10 times this scale capable of processing up to 2 300 kg / h integrated with a 1.3 MW diesel generator running on bio-oil for a process output of over 70 % by weight bio-oil. This will enable the AG members, the forest owners to either process them-selves or sell to other processors of the forest floor residue that is currently unused, into valuable bio-oil and char as a CO2-neutral fossil fuel replacement. It is desirable to maximise the pyrolysis oil and minimise char and gas as the oil has the highest value. 230 kg / hr is selected because the plant needs to be of a certain minimum size to be scalable to the desired capacity of 2 300 kg / h (which again is a reasonable trade-off between mobile size and operator cost). We can eliminate very small (i.e. 20 kg / h) systems because the materials handling and feeding will not be scalable at these throughputs.
Our scientific objectives were to:
- investigate the dielectric (microwave heating) properties of the feedstock with different samples of wood and varying moisture content, and to investigate the dielectric properties of intermediates and pyrolysis products formed during the process and under process conditions (different densities; enhanced temperatures etc);
- investigate the pyrolysis product quality and microwave power density requirements for treatment times down to less than 1 s;
- build a three-dimensional simulation model in order to visualise the interactions between the electromagnetic field and the process materials in a range of conceptual microwave cavities suitable for continuous processing;
- understand how the microwave pyrolysis products vary as a function of the raw material parameters (moisture content, feedstock size and type) and process conditions (power and residence time).
Our technical objectives were to:
- design and build a reaction chamber with feeding (microwave cavity) which gives an electric field distribution which can heat the feedstock evenly in < 1 s to 500 degrees of Celsius to minimise char formation;
- design and build a solids handling system with controlled drying and preheating capable of more than 230 kg / h continuous operation, which can be integrated with the microwave cavity and vapour recovery systems;
- design and build an automated control system with multipoint temperature measurements with time constant < 50 ms and feed rate control capable of closed loop control of the process to within +/- 200 degrees of Celsius to maximise liquid yields and to prevent carbonisation and gasification;
- design and build a vapour condensation system limiting the residence time in the chamber and quenching the vapour to limit gas formation and maximise liquid yield with a capacity of 120 l / h;
- design and build an inert gas system utilising recycled pyrolysis gas to limit inert gas consumption to an average of less than < 30 l / h or less than 3 bottles (80 l / 300 bar) of N2 per month in continuous operation.
Our integration goals were to:
- design and construct a scalable 230 kg / h continuous prototype reactor for < 1 s pyrolysis and > 70 % efficiency to prove the concept;
- achieve repeatable product quality < 5 % variation in distribution between oil/char/gas from batch to batch;
- achieve a process able to repeatable produce pyrolysis liquid levels > 70 % of wood weight;
- achieve scalability to a reactor chamber design for 2 300 kg / h and max. 1 000 kW microwave power for a plant with a manufacturing cost in serial production lower than EUR 1 750 000 including parts and fit in two 40'' ISO containers.
Our other objectives were:
- Innovation: To protect intellectual property rights (IPRs) produced and patent and exploit the technologies, to establish a supply chain to exploit the technology and to develop a future funding and investment plan.
- Dissemination: To disseminate the know-how produced within the consortium and (if appropriate) outside it.
Project results:
At the start of the project, we characterised the dielectric properties of two forestry waste samples at two industrially-allocated frequencies and at temperatures from 20-800 degrees of Celsius. Two measurement techniques were used, based upon a cavity perturbation method to give accurate dielectric property readings at all temperatures. The dielectric constant and dielectric loss factor both vary significantly with temperature at both frequencies, and the behaviour is explained based on the water content and the degree of graphitisation due to combustion.
The findings of D1.1 indicate that all forest waste materials absorb microwave energy strongly at temperatures > 600 degrees of Celsius, once the material pyrolyses. When this occurs, a phenomenon known as 'thermal runaway' will take place, where temperatures well in excess of 1 000 degrees of Celsius can be achieved in seconds. These temperatures are sufficient to melt quartz reactor vessels, so a dedicated microwave heating system is required for the batch microwave pyrolysis experiments.
Thus microwave pyrolysis of forest wastes can be achieved without the use of microwave-absorbing additives. High-power densities and short residence times are required to promote bio-oil yields and maximise the efficiency of the process.
All materials handling technologies were evaluated and four continuous processing concepts were shortlisted. Electric field simulations showed that a belt conveyor is able to achieve a power density which is very high and evenly distributed and low residence times, but only for feedstocks that are very closely-controlled. Other systems have disadvantages in the power density distribution and residence time but are able to process a wider range of materials.
In work package (WP) 2, we confirmed that we were able to design a microwave pyrolysis plant with feeding system for continuous processing of forest residues. WP3 concentrated on the MICROFUEL monitoring system - the design and building of an automated control system with different sensors and multipoint temperature measurements with time constant < 50 ms and feed rate control capable of closed loop control of the process to within +/- 200 degrees of Celsius to maximise liquid yields and to prevent carbonisation and gasification.
The monitoring system we developed is a PLC system, with the process picture and process values presented on a computer screen. The PLC and the computer form the process control system (PCS). The system also interacts with the motor control system (MCS), which controls all the power circuits (motors, heaters, magnetrons etc).
The main individual loops, indications and alarms developed for the MICROFUEL monitoring system related to the MICROFUEL process functioning and systems are:
- raw material infeed hopper level system;
- screw conveyor drive;
- oxygen control;
- reactor temperature indication and control;
- pressure control and monitoring;
- turntable speed control;
- carbon cooler temp. control;
- recirculation gas temperature;
- process vapour pressure control;
- column fluid level control;
- settling tank level control;
- scrubber level control;
- system pressure control;
- gas emergency shutdown (ESD) relieve control;
- flare knock-out drum condensate level;
- flare gas flow indication;
- flare burner temperature;
- inert gas pressure;
- plant air pressure;
- cooling medium instrumentation.
The objective of WP4 was to design and build a vapour condensation system limiting the residence time in the chamber and quenching the vapour to limit gas formation and maximise liquid yield with a capacity of 120 litres per hour. Furthermore, to design and build an inert gas system utilising recycled pyrolysis gas to limit inert gas consumption to an average of less than 30 litres per hour or less than 3 bottles of N2 per month in continuous operation.
D4.1 described the prototype, designs and tests of MICROFUEL's gas and vapour system. The results confirmed that the initial idea was feasible and possible with different approaches. Therefore, the simulation and design are fulfilled, but the installation was not been finalised, due to delay in manufacturing the rest of the prototype - in the event, a much simpler condenser was used to condense the gases evaporated from the pyrolysis of wood chips.
In WP5, we integrated the entire MICROFUEL system. There were many technical delays in the project, so a working prototype was produced only at the end. We were not able to produce bio-oil and biochar continuously from wood chips. However, we have been able to design and build an m/w pyrolysis plant which can produce both bio-oil and biochar from wood chips on a batch basis - so the overall goals were partially met:
- A flammable bio-oil was produced, along with very light and (most likely) activated biochar. However the overall pyrolysis process was still under development at the project close.
- The bio-oil produced shows a high enough calorific value to be able to burn when heated.
- At the end of the technology development phase of this project, the technology is still in need of further refinement, if it is to be used in continuous operation, rather than batch mode.
- As continuous operation was not possible, a true capacity figure is difficult to estimate. However, tests so far indicate that a throughput of 400-500 kg / h is possible with the current design and configuration. The results presented show that it is likely that a full scale continuous mode plant will have a capacity of 2 000 kg / h, using 400 kW m/w power.
- The foot print of the system is small enough to fit into two 20' ISO shipping containers. We have thus produced a working prototype, with the potential for good transportability, capable of remote operations deep within Europe's forests.
Technical delays meant that at the close of the project, not all of the objectives were met, due to several serious integration delays. However, all subunits have been manufactured and tested. There were notable issues with some subunits:
- Cracking of ceramic plates in the reactor.
- The systems for feeding in woodchip feedstock and extracting char did not meet the specifications set out in the request for quotation. This meant that we were unable to operate the prototype in continuous mode.
- The monitoring and control system was not fully integrated or tested.
- A liquid-to-solid yield ratio was estimated to about 50:50 (by weight), but no validation or process repeatability data can be given at this stage.
We have made extensive recommendations for how this basic prototype can be refined in further trials.
We were able to produce several samples of bio-oil from the flash pyrolysis of wood chips.
Three samples of this bio-oil have been analysed to determine their contents and properties.
The analysis determined that the samples:
- would ignite in simple combustion tests;
- had combustion temperatures of between 400-520 degrees of Celsius, confirming suitability as a fuel;
- contained a range of volatile compounds from wood, including alkyl groups, aromatics, anilines, aromatic esters, ketones, amide and aromatic aldehydes; and
- contained further semi-volatile compounds, such as cresols and vanillin, which could be useful platform or speciality chemicals in any large-scale process.
Potential impact:
Cost-benefit analysis:
In terms of cost benefit analysis, with modifications, the estimated price tag for a full-scale MICROFUEL system (using 4 microwave generators, rather than the single unit demonstrated in this project) would be EUR 1 300 000 per unit. Selling price would be around EUR 2 200 000 per unit.
In economic terms, the total system (MICROFUEL unit, plus pre-drying equipment, gas-powered generator and civil engineering costs) would use wood waste as a fuel source to produce both bio-oil and biochar. Operating at full capacity, estimated payback period would be a respectable 3.3 years. Such a plant would be capable of producing 8 700 tons of bio-oil per annum - at May 2012 prices; this would have a value of EUR 3.2 million. As a by-product, a further 6 000 tons of biochar could be sold to the ferrosilicon industry. (Ferrosilicon is produced by the reduction silica with carbon in the presence of scrap iron). To the Norwegian ferrosilicon sector, the biochar would have a value of EUR 1.8 million.
In terms of CO2 balance, the bio-oil produced by such a plant represents a potential reduction of 16,600 tons of CO2 emissions per year. If the bio-gas is used fully, this would represent a further 25,509 tons of equivalent emissions reduction. If the biochar was used for sequestration, rather than for industrial uses, then the CO2 sink potential represents further 18 412 tons in reduced emissions.
Dissemination:
Limited information on the project is available on the public page of the project's website. Most partners have publicised the project at annual general meetings, in press releases or at conference and these activities are summarised here. One peer-reviewed paper was published.
Internal dissemination activities:
Throughout the project, partners have used the projects website www.micro-fuel.eu for internal dissemination of meeting notes, technical discussions, design drawings and the formal deliverable reports (both in draft and in final versions). D7.1 (Project website) summarises these activities. The website has a public page, where basic information on the project is given. There is also a contact listed for people requesting more information.
The website has received considerable interest and one enquiry. (For example, on 20 July 2012, the project was approached by a consultant in Brazil who wished to represent the project and the consortium in that region. On 21 August 2012, a similar request was received from the Philippines. In both cases, the interest was in using the technology for pyrolysis of crop waste biomass - bagasse and rice husks / straw).
Partners have met regularly during the project to discuss progress. At their final meeting (M41, in Notodden in Norway), the researcher team presented the final working prototype to the consortium.
External dissemination activities
The MICROFUEL team have made several demonstrations of their technology in open days or to visitors at the Notodden pilot plan. As an example, on 6 March 2012, the team received a visit Norway's Environment Minister, Mr Erik Solheim.
Basic information on the technical success of the project was issues as a press research on 23 May 2012. This included some basic pictures of the pilot plan and a description of the relevance of the project to the forestry industry. A link to the press release was inserted into the project web sites home page. Each partner has made use of the press release in different ways.
Partner activities
- Nor-Tek: On 25 June 2012, details of the project we published in English in Pera News; Pera is Nor-Tek's parent company). Pera News has a weekly circulation of 9 631 (August 2012 figures). In July, Pera drafted a case study on the project, based on information outlined in the website. The case study highlights the benefits of a consortium of different European organisations developing technology through Framework.
- CGS: In June 2012, CGS mentioned the project on their web site. University of Nottingham: The team presented a paper at the AMPERE 2011 conference in Toulouse. This presentation covered some aspects of the MICROFUEL project. In 2010, the published a paper in the journal Industrial & Engineering Chemistry Research. This is a peer-reviewed journal has an impact factor of 2 237 and 34 547 annual citations in 2011.
- EPFU: Cited the project on their home page. Staff from EPFU have presented details of the project to 829 Estonian forestry owners at events such as the general meeting, forest owners' reunions and forest tent events. These tent events take place within Estonian forests and involve local communities.
- NFOF: Reported on the start of the project in a news item on their website. The project has also been highlighted in two articles in NFOFs in-house magazine (Skogeiern), which has a circulation of 40 000. This newsletter is read widely throughout the Norwegian forestry industry. In June 2012, NFOF covered the project at their annual conference of forestry owners in Norway ('Skog og Tre').
- COSE: Held some specialist dissemination activities within the Spanish forestry sector.
- Thermya: Reported no dissemination activities.
- Pymetal: Reported no external dissemination activities.
- CEPF: Arranged some specialist dissemination activities for European forestry managers.
- GSD: Reported no external dissemination activities.
- Sairem: Reported no external dissemination activities.
- SBC: Covered the project on their web site.
List of websites: http://www.micro-fuel.eu