COST VERSUS SCALE FOR ADVANCED PLANTATION-BASED BIOMASS ENERGY SYSfEMS IN . THE U . s .

A unique feature of biomass energy systems is that the feedstock must be gathered from a wide area around the energy production facility. For a small-scale facility, transport costs will be relatively low, but capital cost per unit of output will be high. For a large-scale facility, b"ansport costs will be high, but capital costs will be relatively low. At some intermediate scale, the total cost of energy should reach a minimum. This paper examines the effects of scale on the prospective costs of producing electricity and alcohol fuels from plantation-grown switChgrass in the North Central and Southeast regions of the US. Site-specific biomass cost-supply cmves for the year 2000 and 2020 are developed using projections of the Oak Ridge National Laboratory for switchgrass yields and costs as a function of land capability class. A geographic information system (GIS) is used to analyze soil quality distributions and road transport distances. Conversion technologies considered include one commercial electricity generating technology--the steam rankine cycle--and one nearing commercial readiness.-the gasifier/gas turbine combined cycle. Two alcohol fuels are considered: methanol via thermochemical gasification and ethanol via enzymatic hydrolysis. Both of these processes have the potential to be commercially ready early in the next century or sooner. Estimates of installed capital costs for all of these conversion systems drawn from published and other sources. In all cases. the minimum cost of elecbicity (COB.;.) or alcohol (Coy is reached at plant capacities that are larger than conventional wisdom might suggest. Up to these capacities. the rate of decrease in unit capital costs is more rapid d1an the rate of increase in biomass transportation costs. However. around the capacity corresponding to CO~ or CO~. there is a wide range over which costs change very little. In general. higher biomass yields lead to larger capacities at COE... or CO~ Costs are higher in the NC than SE region. and (in both regions) costs are lower using year-2020 biomass costs compared to year-2000 costs.