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Swiss researchers develop new biomass conversion pathway for biojet fuels

In Switzerland, researchers at Berne University of Applied Sciences (BFH) have developed a new technology pathway for the production of aviation biofuels from lignocellulosic biomass and assessed its sustainability in the Swiss context.

Refuelling of a turboprop aircraft.

The aviation industry has set an aspirational goal to reduce its carbon dioxide (CO2) emissions by 50% in 2050, compared to 2005, without limiting growth. Central to this vision is a near-complete shift from conventional jet fuel to alternative aviation fuels that thus far are proving costlier to produce. A recently completed Swiss research project has developed a technology platform comprising of subsequent biochemical and catalytic conversion processes for the production of biojet fuels from lignocellulosic biomass.

Aviation will continue to rely on liquid fuels with high energy density in the future. Lignocellulosic biomass has the potential to address both needs, but finding conversion routes to jet fuels or commodity chemicals is challenging.

Production of fuels and commodity chemicals through subsequent biochemical and catalytic conversion of lignocellulosic biomass” is a recently completed Swiss research project funded under the National Research Programme (NRP) Energy Turnaround scheme (NRP 70), that has developed a technology platform comprising of subsequent biochemical and catalytic conversion processes for the production of biojet fuels from lignocellulosic biomass.

Lactate platform

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) at Berne University of Applied Sciences (BFH) 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, for instance, 196.5 kg butyric acid per tonne of beech wood.

In the catalytic upgrading process olefin selectivities > 90 percent at close to 99 percent 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.

Ample biomass feedstock available

The sustainability analysis showed that the potentially available herbaceous biomass in Switzerland could reach a quantity of 500 000 tonnes of dry matter per annum. 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, such as 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 tonnes of biomass intake was estimated at CHF 3.6 per litre, which is about twice the current kerosene price but in agreement with price forecasts for other biomass-based production routes.

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