Department of Civil and Environmental Engineering, University of California, One Shields Avenue, Davis, California 95616, United States.
Environ Sci Technol. 2012 Mar 6;46(5):2557-63. doi: 10.1021/es203098j. Epub 2012 Feb 22.
Beginning with model year 2012, light-duty vehicles sold in the U.S. are subject to new rules that regulate tailpipe greenhouse gas (GHG) emissions based on grams of CO(2)-equivalent per mile (gCO(2)e/mi). However, improvements in vehicle technology, lower-carbon fuels, and improvements in GHG accounting practices which account for distortions related to emissions timing all contribute to shifting a greater portion of life cycle emissions away from the vehicle use phase and toward the vehicle production phase. This article proposes methods for calculating time-corrected life cycle emissions intensity on a gCO(2)e/mi basis and explores whether regulating only tailpipe CO(2) could lead to an undesirable regulatory outcome, where technologies and vehicle architectures with higher life cycle GHGs are favored over technologies with lower life cycle emissions but with higher tailpipe GHG emissions. Two life cycle GHG assessments for future vehicles are presented in addition to time correction factors for production and end-of-life GHG emissions. Results demonstrate that, based on the vehicle designs considered here, there is a potential for favoring vehicles with higher life cycle emissions if only tailpipe emissions are regulated; moreover, the application of time correction factors amplifies the importance of production emissions and the potential for a perverse outcome.
自 2012 年车型年开始，美国销售的轻型车辆将受到新规定的约束，这些规定根据每英里二氧化碳当量克数（gCO(2)e/mi）来规范尾气温室气体（GHG）排放。然而，车辆技术的改进、低碳燃料的使用以及对计入与排放时机相关扭曲因素的温室气体核算方法的改进，都促使生命周期排放的更大一部分从车辆使用阶段转移到车辆生产阶段。本文提出了一种基于 gCO(2)e/mi 计算时间校正生命周期排放强度的方法，并探讨了仅监管尾气 CO(2)是否会导致不理想的监管结果，即生命周期 GHG 较高的技术和车辆架构相对于生命周期排放较低但尾气 GHG 排放较高的技术更受青睐。本文除了提出生产和报废阶段温室气体排放的时间校正因子外，还对未来车辆的两种生命周期温室气体评估进行了介绍。结果表明，基于此处考虑的车辆设计，如果仅监管尾气排放，则有可能青睐生命周期排放较高的车辆；此外，时间校正因子的应用放大了生产排放的重要性以及出现反常结果的可能性。
