Bioenergy sources

FIGURE 17.22 Distribution of bioenergy sources worldwide. The predominance of wood energy, primarily for cooking and heating in less developed countries, is obvious. 

The sources of biofuels and the methods for bioenergy production are too numerous for an exliaustive list to be described in detail here. Instead, electricity production using direct combustion, gasification, pyrolysis, and digester gas, and two transportation biofuels, ethanol and biodiesel, are discussed below. 

In the United States about 3 percent of all electricity produced comes from renewable sources of this a little more than half comes from biomass. Most biomass energy generation comes from the lumber and paper industries from their conversion of mill residues to in-house energy. Municipal solid waste also is an important fuel for electricity production approximately 16 percent ot all municipal solid waste is disposed of by combustion. Converting industrial and municipal waste into bioenergy also decreases the necessity for landfdl space. 

Another emerging area m biofuels is pyrolysis, which is the decomposition of biomass into other more usable fuels using a high-temperature anaerobic process. Pyrolysis converts biomass into charcoal and a liquid called biocrude. This liquid has a high energy density and is cheaper to transport and store than the unconverted biomass. Biocrude can be burned in boilers or used in a gas turbine. Biocrude also can be chemical by altered into other fuels or chemicals. Use of pyrolysis may make bioenergy more feasible in regions not near biomass sources. Biocrude is about two to four times more expensive than petroleum crude. 

Because of limits on the amount of land accordingly available for growing plants that can be used for energy, bioenergy cannot be viewed globally as the sole replacement or substitute for fossil fuels, but rather as one element in a broader portfolio of renewable energy sources [1]. In rural locations in developing countries without current access to electricity, however, biomass can provide a transformative local power source. 

Source Adapted from Kosaric, N. et al., Ethanol from Jerusalem Artichoke Tubers, paper presented at Bioenergy R D Seminar, Winnipeg, Canada, March 20-31, 1982 Kosaric, N. and Vardar-Sukan, F., in The Biotechnology of Ethanol Classical and Future Applications, Roehr, M., Ed., Wiley-VCH, New York, 2001, pp. 90-226. 

In the Netherlands a goal to produce 120 PJ of electricity from sustainable sources in the year 2020 is set by the government This corresponds to 10% of the total energy production in the Netherlands, of which 50 PJ is designated to come from (in)direct co-combustion and stand-alone bioenergy plants. Direct and indirect co-combustion of biomass and waste streams with coal are considered cost-effective alternatives to achieve this target. 

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