Emission of CO2 from energy crop production

The production of cellulosic energy crops (e.g., short rotation woody crops and herbaceous crops) make a net contribution of CO2 to the atmosphere to the extent that fossil-fuel based inputs are used in their production. The CO2 released from the use of the biomass is merely CO2 that has recently been removed from the atmosphere by the plant growth process. Fossil inputs used in the production of energy corps include energy invested in fertilizers and pesticides, and petroleum fuels used for machinery operation such as site preparation, weed control, harvesting, and hauling. Fossil inputs used come from petroleum, natural gas, and electricity derived from fossil sources. No fossil inputs for the capital used to produce fertilizers, pesticides, or machinery is calculated in this analysis. In this paper calculations are made for the short rotation woody crop hybrid poplar (Populus spp.), the annual herbaceous crop sorghum (Sorghum biocolor [L.] Moench), and the perennial herbaceous crop switchgrass (Panicum virgatum L.). For comparison purposes, emissions of CO2 from corn (Zea mays L.) are calculated