A factorial design analysis of a biomass to ethanol production system

Abstract

A least cost, dynamic programming solution was derived by an algorithm for ethanol production from woody biomass. Conversion of the feedstock was based on an enzymatic hydrolysis/fermentation process. The final cost of ethanol from this system, prior to any sensitivity analysis, was $0.45 L −1. A sensitivity analysis, using a factorial design, compared the relative impact of various model parameters on production costs. The factorial design analysis can be used as a guide for lowering final product costs. Three factors were incorporated into the first factorial design: the size of the manufacturing facility, storage retention, and the price of alternative feedstocks. Each of the main factors had an impact on the solution cost. Facility size had the largest effect, representing 45.3% of total cost variability. Storage deterioration and the price of alternative feedstocks had lower effects of 17.4% and 17.6%, respectively. The largest interaction effect, at 17.4%, illustrated that storage deterioration and facility size have a joint effect on production costs. The second factorial design employed five factors. Ethanol yield from the woody feedstock accounted for 44.0% of the total variability in final product cost. Harvesting equipment capability placed a 36.8% effect on the final product cost. The third largest effect, at 8.7%, was plantation yield. Although plantation yields are of key importance to feedstock prices, they had a lesser impact than the other factors on the final product cost over an entire production process. Storage retention and facility size had a reduced impact on total costs when considered in combination with other design factors. Based on this study the focus for research and technological improvements should be on conversion yields from wood, harvester equipment capabilities, and plantation yields.