An investigation of the technical and economic aspects of tapping solar energy stored in plants and organic wastes to provide an alternative to the dwindling resources of fossil fuels. The amounts of energy that might be derived from conventional crops, trees, and algae are compared, as well as the costs of producing such energy and converting it to fuel. Three conversion methods are described: anaerobic bacterial fermentation which forms methane, yeast fermentation (ethyl alcohol), and pyrolysis (fuel oil). Some of the implications of a large-scale agro-energy industry are also examined. Conclusions are that the 300 million acres of uncultivated cropland and woodland in the United States could produce enough vegetation to provide more than half the current gas demand (based on 60 percent efficiency). Organic wastes, when converted to methane, would amount to about 10 percent of the annual gas demand. While fuel produced from crops is not presently economically competitive with oil and natural gas, it may become more attractive as petroleum resources are depleted. 24 pp. Ref.