Abstract

In 2010, the U.S. Environmental Protection Agency (EPA) released a life-cycle analysis of the greenhouse gas (GHG) emissions associated with the production and combustion of corn ethanol. EPA projected that by 2022, the emissions profile of corn ethanol from a new refinery would be 21% lower than that of an energy equivalent quantity of gasoline. Since 2010, the 21% value has dominated policy discussions and federal regulations related to corn ethanol as a renewable fuel and a GHG mitigation option. It is now 2018 and new data, scientific studies, technical reports, and other information allow us to examine the emissions pathway corn-ethanol has actually followed since 2010. Using this information, we assess corn ethanol's current GHG profile at 39–43% lower than gasoline. We also develop two projected emissions scenarios for corn ethanol in 2022. These scenarios highlight opportunities to produce ethanol with emissions that are 47.0–70.0% lower than gasoline. Many countries are now developing or revising renewable energy policies. Typically, biofuel substitutes for gasoline are required to reduce GHG emissions by more than 21%. Our results could help position U.S. corn ethanol to compete in these new and growing markets.

摘要

2010年，美国环境保护署（EPA）发布了与玉米乙醇生产和燃烧相关的温室气体（GHG）排放的生命周期分析。EPA预计，到2022年，新炼油厂的玉米乙醇排放量将比同等量的汽油低21％。自2010年以来，21％的价值主导了有关玉米乙醇作为可再生燃料和温室气体减排方案的政策讨论和联邦法规。现在是2018年，新的数据，科学研究，技术报告和其他信息使我们可以检查自2010年以来玉米乙醇实际遵循的排放途径。利用这些信息，我们估计玉米乙醇当前的温室气体排放量降低39–43％比汽油。我们还制定了两个预计的2022年玉米乙醇排放情景。这些情景突出显示了生产乙醇的机会，其排放量比汽油低47.0–70.0％。现在许多国家正在制定或修订可再生能源政策。通常，需要用生物燃料替代汽油以将温室气体排放量减少21％以上。我们的结果可能有助于美国玉米乙醇在这些新兴市场中竞争。