The biomass species selected as energy crops and the climate must be compati­ble to sustain operation of the energy or fuel farm under human-controlled conditions. Wild stands of biomass are also amenable to harvesting as energy crops and are still the primary sources of virgin biomass feedstocks because large-scale energy and fuel farms in which dedicated biomass energy crops are grown have not yet been established. The few attempts that have been made to design, build, and operate such farms have not been too successful. The compatibility of biomass and climate is, nevertheless, essential to ensure that these systems can ultimately be operated at a profit on a commercial scale. The three primary climatic factors that have the most influence on the produc­tivity and yields of an indigenous or transplanted biomass species are insolation, precipitation, and temperature. Natural fluctuations of these factors remove them from human control, but the information compiled over the years in

meteorological records and from agricultural and forestry practice supplies a valuable data base from which biomass energy systems can be conceptualized and developed. Of these three factors, precipitation has the greatest impact because droughts can wreak havoc on biomass growth. Fluctuations in inso­lation and temperature during normal growing seasons do not adversely affect biomass growth as much as insufficient water. Ambient carbon dioxide (C02) concentration and the availability of macronutrients and micronutrients are also important factors in biomass production.