Forest-based biomass, products from

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. 

Various Products From Forest-Based Biomass... 

Biomass potentials are mainly determined by agricultural productivity and the amount of land accessible for energy crop production. The total area under energy crops in the EU was around 1.6 million hectares in 2004 (estimate for 2005 2.5 million hectares), which represents nearly 3% of the total arable land. AEBIOM (2007) estimated a total biomass supply of 220 MtOE for the year 2020, while 23 MtOE are covered by wood-based bioenergy (direct from forests) and 88 MtOE by agriculture-based energy crops (by-products not considered). The Commission has estimated that about 15% of the EU s arable land (17.5 million hectares) would be used to reach the targets for 2020. 

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. 

The platform chemicals described earlier mainly rely on feedstock, for instance, 70% of the total cost of the fermentation product is based on feedstock. Hence substrate costs are the most influential parameters in platform chemical production from renewable resources. The cost of the substrate is not only based on pretreatment and fractionation but also on the severe environmental damage caused by deforestation for feedstock requirements (Octave and Thomas, 2009). As mentioned earlier, to get a few hxmdred kilograms of chemicals, a huge ton of forest biomass is consumed. Hence the biorefinery sector should divert its focus from wood to forest wastes, paper mill wastes, agricultural residues, and other municipal wastes. This will decrease the pressure on forest biomass and make the entire process sustainable. In order to reduce deforestation, a few strategies are to be followed in biorefineries ... 

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. 

All estimates for particle production due to forest fires and biomass burnings are based on experimental emission factors combined with statistical data for the global consumption rates for the materials involved. The most detailed study has been made by Seiler and Crutzen (1980). They deduced a particle production rate from forest fires alone of 100 Tg/yr. Including agricultural biomass burnings raises the rate to about 200 Tg/yr, a value approaching that for mineral dust emissions. This is much higher than all earlier estimates. 

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