Assessment of Biofuels in California and Potential for Future Utilization

This study analyzed the potential energy resources contained in the biomass residues from the leading crops and livestock in California. As compared with an earlier similar study by Knutson and Miller (1982), where a total of 24 million tons of biomass was reported having an energy value of 336,000 billion Btu’s, this current study showed a total of over 18 million tons (excluding 7.2 million tons of lumber mill and forest slash residues), which translates to almost 13 million tons of dry matter. The energy value of this biomass is 189,000 billion Btu’s, about 56 % of the 1982 value. The reasons for this difference include less acreage of field crops which yield more residues than tree and vegetable crops, as well as utilization of some of these residues for alternative purposes. Further, the more conservative total energy figure is based on realistic estimates of the moisture contents of the various crop animal residues. The crop residues were divided into “wet residues” including cattle and poultry manure, lettuce, tomato and vegetable residues totaling 4,961,787 tons of equivalent dry matter; and the other “dry residues” including wheat, rice, cotton, corn and all tree crop residues totaling 7,881,256 tons of dry matter. If a dry biomass steam boiler and electric generator system presently being used at a major walnut processor in California is used as the model for converting all the dry residues to electricity and steam, then the dry residues could be converted to over 6 billion whirs worth over $660 million. The steam byproduct would be worth an additional $70 million. Thus for all the dry residues, the total electricity and steam benefits would amount to $730 million annually. As for the wet residues, these materials could be anaerobically digested to produce methane, which could be used to produce electricity and steam as is presently being done at a large dairy farm and cheese plant in the Central Valley of California. If this dairy manure digester is used as the model for estimating the total energy benefits of all the wet residues in California, the electricity possible is almost 3 billion kwhrs worth almost $328 million annually, and the steam byproduct would be worth $118 million, whose total is also $446,000,000 per year. The total of the wet and dry residue benefit would be $1,176,000,000 at present energy prices; in other words over a $1-billion per year business. This represents a substantial economic opportunity for the agricultural community on California.