Forest-based biomass, products from ethanol

Only a small number of chemicals have been produced from renewable biomass via fermentation. Europe and the United States have planned to produce lactic acid, acetic acid, and ethanol on a commercial scale. Moreover, only these products are currently produced on an industrial scale competing with the petrochemical industry (Danner and Braim, 1999). While the fermentation routes can produce a range of platform chemicals, this process suffers due to the complex and often undesired metabolic pathways of microorganisms. A wide-ranging chemical tfxat can be produced by the fermentation of forest-based biomass is displayed in Fig. 16.2. 

Second-generation biofuel technologies make use of a much wider range of biomass feedstock (e.g., forest residues, biomass waste, wood, woodchips, grasses and short rotation crops, etc.) for the production of ethanol biofuels based on the fermentation of lignocellulosic material, while other routes include thermo-chemical processes such as biomass gasification followed by a transformation from gas to liquid (e.g., synthesis) to obtain synthetic fuels similar to diesel. The conversion processes for these routes have been available for decades, but none of them have yet reached a high scale commercial level. 

If methanol from biomass was used as a substitute for oil (33 quads) in the United States, about 1000 million hectare of forest land per year would be needed to supply the raw material. This land area is much greater than the 162 million ha of United States cropland now in production. Although methanol production from biomass may be impractical because of the enormous size of the conversion plants, it is significantly more efficient than ethanol production using corn based on energy output and economic use of cropland. 

Both in the USA and the EU, the introduction of renewable fuels standards is likely to increase considerably the consumption of bioethanol. Lignocelluloses from agricultural and forest industry residues and/or the carbohydrate fraction of municipal solid waste (MSW) will be the future source of biomass, but starch-rich sources such as corn grain (the major raw material for ethanol in USA) and sugar cane (in Brazil) are currently used. Although land devoted to fuel could reduce land available for food production, this is at present not a serious problem, but could become progressively more important with increasing use of bioethanol. For this reason, it is important to utilize other crops that could be cultivated in unused land (an important social factor to preserve rural populations) and, especially, start to use cellulose-based feedstocks and waste materials as raw material. 

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