Applying Adaptive Agricultural Management & Industrial Ecology Principles to Produce Lower- Carbon Ethanol from California Energy Beets.

摘要

The life cycle assessment of a proposed beet-to-ethanol pathway demonstrates how agricultural management and industrial ecology principles can be applied to reduce greenhouse gas emissions, minimize agrochemical inputs and waste, provide ecosystem services and yield a lower-carbon fuel from a highly land-use efficient, first-generation feedstock cultivated in California.;Beets grown in California have unique potential as a biofuel feedstock. A mature agricultural product with well-developed supply chains, beet-sugar production in California has contracted over recent decades, leaving idle production capacity and forcing growers to seek other crops for use in rotation or find a new market for beets. California's Low Carbon Fuel Standard (LCFS) faces risk of steeply-rising compliance costs, as greenhouse gas reduction targets in the transportation sector were established assuming commercial volumes of lower-carbon fuels from second-generation feedstocks -- such as residues, waste, algae and cellulosic crops -- would be available by 2020. The expected shortfall of cellulosic ethanol has created an immediate need to develop lower-carbon fuels from readily available feedstocks using conventional conversion technologies.;The life cycle carbon intensity of this ethanol pathway is less than 28 gCO2e/MJEthanol: a 72% reduction compared to gasoline and 19% lower than the most efficient corn ethanol pathway (34 gCO2e/MJ not including indirect land use change) approved under LCFS. The system relies primarily on waste-to-energy resources; nearly 18 gCO2e/MJ are avoided by using renewable heat and power generated from anaerobic digestion of fermentation stillage and gasification of orchard residues to meet 88% of the facility's steam demand. Co-products displace 2 gCO2e/MJ. Beet cultivation is the largest source of emissions, contributing 15 gCO 2e/MJ.;The goal of the study is to explore opportunities to minimize carbon intensity of beet-ethanol and investigate the potential contribution of this pathway toward meeting the near-term objectives of California's climate change policy.