Energy From Biomass

Abstract

The most abundant biomass is wood, of which cellulose is a major component. Burning releases directly as heat, solar energy which has been stored in the wood as a result of the process of photosynthesis. It is also possible to convert cellulose to simple sugars which may be fermented to ethanol, a more convenient source of energy a a fuel for internal combustion engines; alternatively, wood may be gasified at high temperature in the presence of steam. The resulting synthesis gas can be catalytically converted into methanol. Neither route to a liquid fuel from cellulosic residues has yet been proved economically feasible. However, alcoholic fermentation of sugar, or glucose obtained by the hydrolysis of starch may provide a commercially viable process for the production of fuel alcohol. Both sugar and starch are agricultural food products which are obtained from cane sugar, maize and cassava. Other sources of fermentable sugars and starch include pineapple, sweet sorghum, sago palm, yams and other root crop. The energy input required to grow and process agricultural products may be greater than the energy yield in the form of anhydrous fermentation alcohol. As a consequence, only sugarcane and possibly sweet sorghum can be regarded as giving a net positive energy yield. Maize and on a more limited scale, cassava, may provide a viable process, given an additional source of low grade energy, as is evident from the successful exploitation of these crops for fuel alcohol production in the US and Brazil.