Gasification and hydrogen enhancement and Fischer-Tropsch (biodiesel)

The biomass-based Fischer Tropsch pathway (bio-FT) is typically referred to as a biomass-to-liquid (BTL) route, though this umbrella term can apply to any route which produces liquid fuel from biomass. In the bio-FT route with hydrogen enhancement, biomass is first gasified into syngas (mostly hydrogen, carbon monoxide and carbon dioxide). Instead of sending the syngas to a water-gas shift (WGS) reactor, as is done in the usual bio-FT route, low-carbon hydrogen is added to the syngas to drive a reverse water-gas shift (rWGS) reaction, converting hydrogen (H2) and carbon dioxide (CO2) into water and carbon monoxide (CO). Sufficient hydrogen is added to ensure a desired H2/CO ratio for Fischer-Tropsch (FT) synthesis. The liquids from the FT reactor are further cleaned and separated into their drop-in hydrocarbon products (diesel, jet, naphtha, etc). The benefit of adding hydrogen is a more efficient use of the carbon in biomass, as the carbon in CO2 is converted into hydrocarbon fuels rather than being either vented (bio-FT route) or captured and stored (bio-FT w/ CCS route). Rather than providing negative emissions, the additionally converted carbon can displace fossil carbon within the energy system. Technical challenges revolve around tar buildup and removal during gasification. Bio-FT kerosene (biojet) is a American Society for Testing and Materials (ASTM)-certified sustainable aviation fuel (SAF), allowed to be blended up to 50%.