The production of fuels from biological substrates

Abstract

Ethanol can be obtained from a range of crops currently grown in Ireland. The optimal choice depends on the assumptions made relating to feedstock production costs, ethanol yield and by-product credits. Significant economies in processing costs can be made by maximizing the annual throughput of the plant. This could be achieved by using a multi-feedstock plant but switching feedstocks does not significantly alter their overall cost. The most favourable feedstocks are beet and cereals. The possibility of simultaneously processing these feedstocks for food and energy might be feasible. Producing methanol from crops is more uncertain. Wood from forest thinnings, and straw from cereals and oilseed rape is available, but scarce and irregular supplies inhibit the development of a viable industry. Short rotation forestry (SRF) could provide a feedstock but production costs are uncertain. Feedstock transport costs are high, hence the economies of scale in processing are largely counterbalanced by increased transport costs in procuring the extra feedstock. Producing rape oil as a diesel substitute is very dependent on plant size. The quantities currently grown could only justify a small plant but if production were expanded significantly, or supplemented with imports, a larger plant could be justified.