Economic feasibility and environmental life cycle assessment of ethanol production from lignocellulosic feedstock in Pacific Northwest U.S.

Abstract

Bioethanol produced from the lignocellulosic feedstock is a potential alternative to fossil fuels in transportation sector and can help in reducing environmental burdens. Straw produced from perennial ryegrass (PR) and wheat is a non-food, cellulosic biomass resource available in abundance in the Pacific Northwest U.S. The aim of this study was to evaluate the economic viability and to estimate the energy use and greenhouse gas (GHG) emissions during life cycle of ethanol production from PR and wheat straw. Economic analysis of ethanol production on commercial scale was performed using engineering process model of ethanol production plant with processing capacity of 250 000 metric tons of feedstock/year, simulated in SuperPro designer. Ethanol yields for PR and wheat straw were estimated 250.7 and 316.2 l/dry metric ton biomass, respectively, with annual ethanol production capacity of 58.3 and 73.5 × 106 l, respectively. Corresponding production costs of ethanol from PR and wheat straw were projected to be $0.86 and $0.71/l ethanol. Energy and emissions were calculated per functional unit which was defined as 10 000 MJ of available energy in fuel at the pump. Fossil energies were calculated as 4282.9 and 2656.7 MJ to produce one functional unit of ethanol from PR and wheat straw, respectively. The GHG emissions during life cycle of ethanol production from PR and wheat straw were found to be 227.6% and 284.3% less than those produced for 10 000 MJ of gasoline. Results from sensitivity analysis indicated that there is a potential to reduce ethanol production cost by making technological improvements in pentose fermentation and enzyme production. The integrated economic and ecological assessment analyses are helpful in determining long-term sustainability of a product and can be used to drive energy policies in an environmentally sustainable direction.