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Next Generation Bio-butanol

Periodic Reporting for period 1 - ButaNexT (Next Generation Bio-butanol)

Reporting period: 2015-05-01 to 2016-10-31

Conventional, first generation biofuels (ethanol and biodiesel) are produced from renewable sources and help reduce our dependence on transportation fuels derived from finite petroleum sources. However, these biofuels show limitations relating to sustainability, high production costs, performance properties and incompatibility with existing infrastructures. Thus, currently some advanced biofuels (for example biobutanol) based on more sustainable feedstocks and more efficient technologies are being developed in order to overcome these limitations and meet sustainability and fuel quality standards.

Biobutanol is an attractive advanced biofuel with superior fuel properties. It fits the existing fuel infrastructure; has a higher energy density (similar to petrol/gasoline) and has shown better performance properties than ethanol and biodiesel; however, it has not yet been established in the market due to some technical and economic barriers. In this project, the aim is to overcome some of those barriers by developing and demonstrating, at pilot scale, a novel integrated process for producing cost-competitive biobutanol from sustainable renewable feedstocks.

The ButaNexT project aims to validate an integrated process to achieve a more efficient production of biobutanol using three representative non-food/feed and low cost lignocellulosic feedstocks (wheat straw, miscanthus and treated organic fraction of municipal solid waste -MSW-) and taking into account technical, economic, social and environmental issues.

In general terms, the idea underpinning the project is based on a holistic approach and comprises the study, validation and optimisation, of each independent stage in the conversion process (i.e: pretreatment, enzymatic hydrolysis, fermentation and product recovery) at lab and bench scale using the three selected feedstocks. Moreover, the biocatalysts (enzymes and microorganisms) required for the biochemical conversion steps will be developed and optimised as well.

Once the individual stages have been optimised and the conversion processes assessed as a whole, the most interesting feedstock in terms of conversion rates will be selected and used to carry out the integration of the individual process stages at pilot scale. Information and data available from these assays will be used for the development of an economic evaluation of the integrated process as well as for environmental and social impact assessment. In parallel a technical study of the performance of butanol as a blend component for conventional fossil fuels (gasoline and diesel) and their respective blends with conventional biofuels (ethanol and biodiesel) will be carried out.

Additionally, a technical, environmental and social impact assessment will be performed in order to evaluate the economic feasibility of a future scale-up of the process and also other relevant issues as greenhouse gas (GHG) emissions, energy efficiency and social impacts.
The main results achieved so far are:

• Two-stage pretreatment: including a biomass milling step to significantly reduce particle size, and mild thermochemical stage with overall lower energy balance that improves the rheological behaviour of the slurry and its catalytic conversion.

In the period, a prototype for the physical pre-treatment stage for an efficient micronising step to precisely control particle size output in the range of 150-450 µm has been designed and constructed. At the end of the period, it is being commissioned and starting tests to validate the technology.

In addition, a new strategy for increasing soluble sugars combining ligninolytic enzymes combined with termo-chemical (TC) pretreatment has been deployed. Preliminary results show an increment of soluble sugars immediately after the TC pretreatment.

• Butanol tolerant strains were developed and tested using fed batch fermentation. Miscanthus and wheat straw enzyme hydrolysates were tested, where the project targets for butanol productivity (> 0.75 g/L.h) and butanol yield (> 0.25 g/g) were met.

• In Situ Product Recovery (specifically organophilic pervaporation) that will allow butanol recovery from the fermentation broth in a solvent-enriched permeate, and the use of more concentrated feedstocks improving the overall water balance and hence the energy consumption in the distillation section compared to conventional distillation processes.

In the period, a lab-scale pervaporation unit was designed and assembled, for fed-batch and continuous fermentation. Additionally, a pilot pervaporation unit for integration with the fermentation pilot equipment has been redesigned and constructed. Commissioning and testing of the unit at the pilot-plant will be performed in the following period.

• Concerning blending, engine performance and emissions, during the period, conclusions about the optimum butanol content in diesel and gasoline blends have been achieved, in addition to a detailed testing of vehicle performances and emissions under ambient and cold temperatures when using butanol blends.

• Regarding the environmental, and social impact assessment, and techno-economic analysis, during the period a detailed analysis of feedstock availability and alternative potential uses and costs has been performed, in addition to a preliminary energy balance and GHG assessment.

• Finally, in terms of the exploitation of the results, a mid-term exploitation plan has been issued during the period, which includes the characterisation of the key results, risk analysis and overall intellectual property rights (IPR) strategy.
ButaNexT aims at producing butanol which is considered a superior fuel to conventional biofuels (ethanol) with improved technical characteristics (energy density essentially equal to gasoline, lower vapor pressure). Lignocellulosic and wastes-based biobutanol is also expected to achieve lower greenhouse gas (GHG) emissions and improved sustainability characteristics compared to fossil fuels and conventional bioethanol. ButaNexT will also validate the blend stock value of butanol with fossil fuels and biofuel-fossil fuel blends (it can be blended with diesel or biodiesel up to 40%, and can be blended with gasoline up to 16% and also with ethanol, potentially even displacing gasoline in an “E-85” ethanol/butanol blend) therefore improving environmental and economic benefits of the final fuels.

A process adapted to use a wide range of lignocellulosic feedstocks and wastes (agricultural residues, organic fraction of municipal solid waste -MSW-, regionally adapted energy crops) will facilitate commercial plant supply planning with subsequent improvements in economic benefits as well as overcoming sustainability concerns.

In particular, ButaNexT will develop and validate the following processes and technologies beyond the state of the art:

• Feedstock pretreatment
• Enzymatic hydrolysis
• Fermentation
• Product recovery
• Butanol blending and performance

In terms of impact, the development of rural areas is considered as a direct consequence of the successful development and implementation and scale-up of the process using locally produced versions of the above-mentioned feedstocks. In this respect, the feedstock versatility of the micro-organisms in the core of the process offers the flexibility to accommodate regionally specific feedstocks.