Fuels from Biomass
Authors: Klass Donald L. 
Published: August 2004

AbstractFUELS FROM BIOMASS.Projections indicate that biomass energy contribution will increase to over 4% of total U.S. primary energy consumption. Land‐ and waterbased vegetation, organic wastes, and photosynthetic organisms are categorized as biomass and are nonfossil, renewable carbon resources from which energy, eg, heat, steam, and electric power, and solid, liquid, and gaseous fuels, ie, biofuels, can be produced and utilized as fossil fuel substitutes. The capture of solar energy as fixed carbon in biomass via photosynthesis is the initial step in the growth of biomass.Human activity, particularly in the developing world, continues to make it more difficult to sustain the world's biomass growth areas. It has been estimated that tropical forests are disappearing at a rate of tens of thousands of hm2per year.The remaining carbon transport mechanisms on earth are primarily physical mechanisms. The great bulk of carbon is contained in the lithosphere as carbonates in rock and comprises 99.9% of the total carbon estimated to exist on the earth. Fossil fuel deposits are only about 0.05% of the total, and the nonfossil energy‐containing deposits make up the remainder, about 0.02%.Biomass carbon is a very small, but important, fraction of the total carbon inventory on earth. It has served as a primary energy source for the industrialized nations of the world; it continues to do so for developing countries. The utilization of biomass carbon as a primary energy source does not add any new carbon dioxide to the atmosphere; it is simply recycled between the surface of the earth and the air over a period of time that is extremely short compared to the recycling time of fossil‐derived carbon dioxide.The energy content of standing biomass carbon, ie, the above‐ground biomass reservoir that in theory could be harvested and used as an energy resource, is about 110 times the world's annual energy consumption. Biomass should be considered as a raw material for conversion to large supplies of renewable substitute fossil fuels. Under controlled conditions, dedicated biomass crops could be grown specifically for energy applications. Although relatively large areas are required, the use of land‐or freshwater‐based biomass for energy applications is still practical. Waste biomass is another large source of renewable carbon supply. Various processes can be used to produce energy or gaseous, liquid, and solid fuels from biomass and wastes. In addition, chemicals can be produced by a wide range of processing techniques. The manufacture of synfuels and energy products from virgin biomass requires that suitable quantities be grown, harvested, and transported to the conversion plant site. Many variables must be considered when selecting the $$$ for operation of a system. Several biomass species meet many idealized characteristics and appear to be quite suitable for energy applications. There are a number of important factors that relate to biomass production for energy applications.There is no biomass species grown and harvested in the United States specifically for conversion to biofuels, with the possible exceptions of feedstocks for fuel ethanol and a few tree plantations.