Life-cycle energy and greenhouse gas emission impacts of different corn ethanol plant types

By Michael Q. Wang, May Wu, H. Huo. 2007

504 citations recorded by the source corpus.

Since the United States began a programme to develop ethanol as a transportation fuel, its use has increased from 175 million gallons in 1980 to 4.9 billion gallons in 2006. Virtually all of the ethanol used for transportation has been produced from corn. During the period of fuel ethanol growth, corn farming productivity has increased dramatically, and energy use in ethanol plants has been reduced by almost by half. The majority of corn ethanol plants are powered by natural gas. However, as natural gas prices have skyrocketed over the last several years, efforts have been made to further reduce the energy used in ethanol plants or to switch from natural gas to other fuels, such as coal and wood chips. In this paper, we examine nine corn ethanol plant types—categorized according to the type of process fuels employed, use of combined heat and power, and production of wet distiller grains and solubles. We found that these ethanol plant types can have distinctly different energy and greenhouse gas emission effects on a full fuel-cycle basis. In particular, greenhouse gas emission impacts can vary significantly—from a 3% increase if coal is the process fuel to a 52% reduction if wood chips are used. Our results show that, in order to achieve energy and greenhouse gas emission benefits, researchers need to closely examine and differentiate among the types of plants used to produce corn ethanol so that corn ethanol production would move towards a more sustainable path.

Subfields: Biomedical Engineering, Pollution

View Paper: https://www.semanticscholar.org/paper/44ac5571a8b52a0da3006d150fca5d3dd3fc59bb

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Citations in the corpus

Agronomic and physiological performances of different species of Miscanthus, a major energy crop. A review (2010, background): “One of the benefits of lignocellulosic biofuel is that it reduces greenhouse gas emissions by 85% compared with reformulated gasoline (Wang et al., 2007).”
Improvements in Life Cycle Energy Efficiency and Greenhouse Gas Emissions of Corn‐Ethanol (2009, methodology): “…however, several recent reports estimate a relatively small net energy ratio (NER) and GHG emissions reduction compared to gasoline (Farrell et al. 2006; Wang et al. 2007) or a net increase in GHG emissions when both direct and indirect emissions are considered (Searchinger et al. 2008).”
Commercial cellulosic ethanol: The role of plant-expressed enzymes (2009, background): “Importantly, cellulosic ethanol can significantly reduce greenhouse gas emissions compared to fossil fuels (Wang et al. 2007).”
Second-best biofuel policies and the welfare effects of quantity mandates and subsidies (2012, background): “On an energy equivalent basis, ethanol typically produces lower GHG emissions relative to gasoline, although this attribute is sensitive to the energy used to fire ethanol refineries [28].”
Economic Optimization of a Lignocellulosic Biomass-to-Ethanol Supply Chain (2012, background): “, 2005) and reduce greenhouse gas emissions by an estimated 86% over gasoline (Wang et al., 2007).”
Two sides of the same coin: consequential life cycle assessment based on the attributional framework (2016, background): “But subsequent studies, with updated data and ethanol coproducts accounted for, converged on that corn ethanol had moderately lower life cycle GHG emissions than gasoline (about 70 versus 90 g CO2e MJ 1) (Farrell et al., 2006; Hill et al., 2006; Kim and Dale, 2008;Wang et al., 2007).”
Effects of US Maize Ethanol on Global Land Use and Greenhouse Gas Emissions: Estimating Market-Mediated Responses (2010, background): “…US maize ethanol production would nearly eliminate carbon benefit of this biofuel relative to typical gasoline (94 to 96 g per MJ; Farrell et al. 2006, Wang 2007), which should perhaps encourage some ethanol producers to transition to more climate-friendly technologies (Plevin and Mueller 2008).”