The proposal described was using methane from biogas. But the microbial decomposition of carbohydrates that creates biogas also creates CO2, in equal molar qua

The proposal described was using methane from biogas. But the microbial decomposition of carbohydrates that creates biogas also creates CO2, in equal molar quantity: (CH2O)2 --> CH4 + CO2 So, if you want to get as much fuel as you can out of the carbon in biomass, you want to use extra hydrogen (and in this case, it would mean they wouldn't have to separate out the methane in the biogas; just add hydrogen and reform the whole mixture). That extra CO2 is available without the need for expensive direct air capture: the plants already captured it. You could even directly hydrogenate biomass (or, perhaps, molecules derived from aggressive depolymerization of biomass) instead of going through biogas. This is Virent's approach. It avoids the need to break all the C-C bonds before recreating them in the synfuel. There have been efforts to use solar energy to directly gasify biomass. A company called Sundrop, out of Colorado, was trying to commercialize this 15 years ago. But then fracking dropped the price of natural gas and it all collapsed; the remnants of the company were bought by Chesapeake Energy (a natural gas producer) not long after.