Well-to-wheels energy use and greenhouse gas emissions of ethanol from corn, sugarcane and cellulosic biomass for US use

Abstract

Globally, bioethanol is the largest volume biofuel used in the transportation sector, with corn-based ethanol production occurring mostly in the US and sugarcane-based ethanol production occurring mostly in Brazil. Advances in technology and the resulting improved productivity in corn and sugarcane farming and ethanol conversion, together with biofuel policies, have contributed to the significant expansion of ethanol production in the past 20 years. These improvements have increased the energy and greenhouse gas (GHG) benefits of using bioethanol as opposed to using petroleum gasoline. This article presents results from our most recently updated simulations of energy use and GHG emissions that result from using bioethanol made from several feedstocks. The results were generated with the GREET (Greenhouse gases, Regulated Emissions, and Energy use in Transportation) model. In particular, based on a consistent and systematic model platform, we estimate life-cycle energy consumption and GHG emissions from using ethanol produced from five feedstocks: corn, sugarcane, corn stover, switchgrass and miscanthus.We quantitatively address the impacts of a few critical factors that affect life-cycle GHG emissions from bioethanol. Even when the highly debated land use change GHG emissions are included, changing from corn to sugarcane and then to cellulosic biomass helps to significantly increase the reductions in energy use and GHG emissions from using bioethanol. Relative to petroleum gasoline, ethanol from corn, sugarcane, corn stover, switchgrass and miscanthus can reduce life-cycle GHG emissions by 19-48%, 40-62%, 90-103%, 77-97% and 101-115%, respectively. Similar trends have been found with regard to fossil energy benefits for the five bioethanol pathways.

Bioenergy production and environmental impacts

“…Among the GHGs, CO 2 and N 2 O are two primary components because of their large quantity and multiapproaches of production (Dunn et al 2013;Qin et al 2016). Theoretically, net CO 2 emissions resulting from the direct use of biofuels are far less than the utilization of fossil fuel, which has been proven by many studies (Dunn et al 2013;Wang et al 2012). By replacing fossil fuel, Liu et al (2017) quantified that the maximum potential switchgrass production on marginal land would reduce emissions by 29 million tons CO 2-eq /year.…”

Exploring impacts of process technology development and regional factors on life cycle greenhouse gas emissions of corn stover ethanol

“…Life cycle studies have evaluated lignocellulosic ethanol production from a variety of feedstocks including: corn stover, switchgrass, hybrid poplar, alfalfa and reed canary grass (e.g., Sheehan et al 2004;Spatari et al 2005;Kim and Dale, 2005;Adler et al, 2007, GonzalezGarcia et al, 2010Wang et al 2012). The studies examined the production and use in road transportation vehicles of ethanol/gasoline blends in the forms of E10 (10 vol% ethanol), E85 (85 vol% ethanol), and E100 (100% ethanol).…”

From Tiny Microalgae to Huge Biorefi neries

“…Recent analysis has shown that sufficient land exists in the U.S. Corn Belt to support a cellulosic ethanol industry without impacting productive cropland [18,39,40]. The effect of dedicated energy crops and corn grain on indirect land use change varies significantly based on the assumptions and models used [13,41,42] but bioenergy crops grown on marginally-productive cropland will have less impact on indirect land use change than bioenergy crops grown on more productive cropland. Likewise, model assumptions underlying direct SOC sequestration will impact system evaluations of GHG emissions and mitigation.…”

“…Biofuels from cellulosic feedstocks (e.g. corn stover, dedicated perennial energy grasses) are expected to have lower GHG emissions than conventional gasoline or corn grain ethanol [9][10][11][12][13]. Furthermore, dedicated perennial bioenergy crop systems such as switchgrass (Panicum virgatum L.) have the ability to significantly increase SOC [14][15][16] while providing substantial biomass quantities for conversion into biofuels under proper management [17,18].…”