Tuesday, June 15, 2010

Boosting Biomass to Fuel Yields


Purdue University researchers discovered ways to increase the "sun to fuel" energy production efficiency up to three times higher than at present.
In the proposed H2Bioil-B process, depending on the efficiency of gasification section, 32-42% of the total biomass is gasified to produce a syngas which is sufficient to hydropyrolyze and hydrodeoxygenate the remaining fraction of the biomass that is directly fed to the hydropyrolysis zone.

The hot gas from the gasifier is directly injected in the pyrolyzer zone. If needed, the temperature of the exhaust gas prior to its injection in the pyrolyzer zone may be adjusted. Also, if required, a hot or a cold recycle stream may be injected between the gasifier and the pyrolyzer zone to provide better temperature control in the pyrolyzer section of the reactor.

The researchers found that while a process such as H2CAR [hybrid hydrogen-carbon process], based on gasification/FT chemistry, can recover nearly 100% biomass carbon, it would also need approximately 0.33 kg H2/L oil produced. On the other hand, fast hydropyrolysis/ HDO-based H2Bioil has a potential to recover ~70% biomass carbon with 0.11 kg H2/L oil.

They estimated the H2Bio-B process is estimated to be able to produce 125-146 ethanol gallon equivalents (ege)/ton of biomass of high energy density oil. The augmented version of fast-hydropyrolysis/hydrodeoxygenation, where H2 is generated from a nonbiomass energy source, is estimated to provide liquid fuel yields as high as 215 ege/ton of biomass. _GCC
This is a novel approach, combining gasification of a portion of the crop with hydropyrolysis of the remainder to apparently achieve higher energy efficiencies than with previous approaches.

Other biofuel makers such as Neste have used hydrogen to boost bioenergy content of bio-oils, and many more proposals for using hydrogen supplementation to make biofuels have been made. The final combination is apt to be different for different companies.

Certainly nuclear energy can generate hydrogen more cheaply and cleanly than virtually any other source of hydrogen. But most farmers and biofuels makers lack their own nuclear reactor for that purpose. Photovoltaics or wind could accomplish the same thing (electrolysis of water for hydrogen), far more expensively, and more intermittently.

All of these calculations from the Purdue team neglect to consider the use of seaweed for biomass -- which allows up to 6 harvests of crop per year. Eventually, marine crops have the potential to eclipse land crops for purposes of biofuels production -- given the appropriate floating infrastructure.

Bonus link: a look at leading bio-butanol producers



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