Completed joint project "Biochemically-catalytically produced biofuels"
A new technology has been developed for the gaining of biofuels for the aviation industry and its sustainability has been assessed.
Aviation will continue to rely on liquid fuels with high energy density in the future. In order to produce such fuels from lignocellulosic biomass, a technology comprising subsequent biochemical and catalytic conversion processes was developed and its future potential economic and environmental sustainability assessed.
To convert all carbohydrate fractions of lignocellulosic biomass, the project team under the stewardship of Dr. Michael Hans-Peter Studer at the School of Agricultural, Forest and Food Sciences (HAFL) developed the lactate platform for producing carboxylic acids. Here, an engineered artificial microbial community funnels the heterogeneous feedstock to lactate as central intermediate, which is then further converted into the target acid(s). The feasibility of this concept was exemplified by producing, e.g., 196.5 kg butyric acid per ton beech wood.
In the catalytic upgrading process olefin selectivities > 90% at close to 99% conversion of carboxylic acids were obtained using a Cu/SiO2-Al2O3 catalyst. A sudden selectivity switch from olefins to predominantly alkanes was observed at full conversion. Carboxylic acids were also successfully upgraded in a single step using Cu/ZrO2 to an organic oil composed of C8 – C16 aromatics and cycloalkenes. This oil is compatible as a 10 vol % blend with Jet A-1 fuel in terms of specific energy and distillation properties.
The sustainability analysis showed that the potentially available herbaceous biomass in Switzerland could reach a quantity of 500,000 tons of dry matter per year. With wood, this figure might be several-fold larger. Thus, the feedstock of a potential biorefinery in Switzerland would be a mix of residual wood, herbal biomass from extensive grassland, harvest residues from agriculture and forest wood that could be utilised without causing environmental damage, i.e. reducing soil organic matter. Based on existing laboratory data (basic technologies, yield, rate) the minimum selling price of lignocellulose based jet-fuel, produced in a pilot facility with an annual capacity of 10,000 tons of biomass intake was estimated at 3.6 CHF/litre, which is about twice the current kerosene price but in agreement with price forecasts for other biomass based production routes.