The FLEXI-GREEN FUELS’ work performed during the project’s lifetime was successful.
The underlying biorefinery concept consists of raw material pre-treatment (organosolv process to process lignocellulosic bioresidues), conversion of sugars to lipids (enzymatic hydrolysis followed by fungal fermentation, algae dark fermentation or lipid rich black soldier fly larva production), valorisation of hemicellulosic sugars via chemical routes, conversion of lignin by fast pyrolysis, chemical upgrading of crude biofuel intermediates (e.g. hydrodeoxygenation, alkylation) and separation into suited drop-in biofuel fractions for aviation and shipping.
With regard to lignocellulosic biomass, residues of beechwood and wheat straw were treated by the organosolv process, a key process to decompose and fractionate the raw materials into its building blocks cellulose, hemicellulose and lignin. Besides crucial insights gained into this process, material fractions have been produced as intermediates for downstream processing/upgrading.
Similarly, significant progress was made with regard to the second targeted bioresidue, namely organic fraction of municipal solid waste, i.e. food waste. The project was able to analyse the composition of this starting material delivered by a municipality on a regular basis, within a whole annual cycle. Enzyme hydrolysis of food waste, cellulose and a mixture of both were performed and optimal processing parameters were identified.
Following the pathway towards aviation and shipping biofuels, FLEXI-GREEN FUELS was able to make significant progress in the transformation of biowaste based cellulosic sugars into lipids. The project could manage to produce lipids by all three paths under investigation: fungal fermentation, algae dark fermentation and by black soldier fly larvae.
The microbial electrolysis cell for biohydrogen production was tested. Key areas for improvement in hydrogen production by MEC were identified, including increased resource utilizations, improvements in time for acclimatization and further operating conditions.
Lignin upgrading by pyrolysis was investigated and the resulting lignin-oil fractions were upgraded downstream by hydrodeoxygenation.
Dehydration of hemicellulose sugars towards furans and their conversion into crude biofuels via aldol condensation reactions was achieved using homogeneous and heterogeneous acid catalysts in aqueous and biphasic systems.
Downstream the hydrotreatments, the resulting crude biofuel intermediates were separated into tailored commercialisable value products to be used as drop-in aviation and shipping fuel. Biofuel fractions with the potential of becoming drop-in fuels for aviation were identified by fuel characterisation.
Furthermore lipid wax from black soldier fly larvae was proven to be suited as marine biofuel for direct use in vessels by engine tests.
Finally, the whole integrated FLEXI-GREEN-FUELS biorefinery was modelled for simulation, optimization and assessments of its technical, economic and environmental performance.
The dissemination activities of the project included a number of peer reviewed open access publications in several scientific journals and additional ones are in preparation.
As exploitation of the convincing FLEXI-GREEN FUELS’ results, a follow-up project is planned to demonstrate this biorefinery concept at higher technical readiness levels.
