Updated energy and greenhouse gas emission results of fuel ethanol

Sep 2005

Energy and environmental effects of using fuel ethanol in the U.S. have been debated since the inception of the fuel ethanol program in 1980. Over the past 25 years, more than 20 studies have been published on the so-called energy balance of corn ethanol. In those studies, energy balance is usually defined as the energy in a gallon of ethanol minus the total fossil energy input (including energy in petroleum, natural gas, and petroleum) consumed to make that gallon of ethanol.
Through the late 1970s to 1980s, several studies concluded that corn ethanol resulted in negative energy balance. But most recent studies now conclude that corn ethanol indeed has positive energy balance, except for a few studies conducted by Pimentel and his co-authors which maintain that corn ethanol still has negative energy balance.
Since the 1980s, the Center for Transportation Research of Argonne National Laboratory has conducted life cycle analyses of energy and emission effects of transportation fuels for U.S. DOE.
With DOE’s  support, Argonne began to develop the GREET (Greenhouse gases, Regulated Emissions, and Energy use in Transportation) model in 1995. The GREET model is a life cycle model for transportation fuels and vehicle technologies. It contains more than 85 transportation fuel pathways. Among them, four are fuel ethanol pathways (corn dry mill ethanol, corn wet mill ethanol, woody cellulosic ethanol, and herbaceous cellulosic ethanol). At present, there are more than 2,000 registered GREET users worldwide.
Since 1997, Argonne has applied, updated, and upgraded the GREET model to evaluate fuel ethanol’s energy and emission efforts relative to petroleum gasoline. In 1997, Argonne published its findings of an ethanol analysis that was conducted for State of Illinois (Wang et al. 1997). Subsequently, with DOE’s support, Argonne continued its effort of analyzing fuel ethanol. In 2003, with support of State of Illinois, Argonne analyzed potential effects of blending ethanol into diesel. This paper presents updated energy and GHG emission results of fuel ethanol that are generated with the most current version of the GREET model.

By: M. Wang (Argonne National Laboratory)

download this document:   476 kb