Blending Carbon Intensity for Ethanol in Gasoline

IF 1 Q4 TRANSPORTATION SCIENCE & TECHNOLOGY
Terrence Higgins, Nigel Clark, Tammy Klein, David McKain
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Abstract

Greenhouse gas emissions reduction from the light-duty transportation fleet is urgent and should address both electric and conventional powertrain technologies. Internal combustion engines will continue to be employed for vehicle propulsion and fleet turnover is slow, encouraging reduction of carbon content in gasoline. Currently ethanol, a renewable fuel, is blended at the 10% level into petroleum to produce finished market gasoline. Ethanol enables a less carbon-intensive petroleum blendstock composition, providing for additional reduction, but this is often overlooked in studies. Carbon intensity, as a ratio of CO2 mass to heat released upon combustion, is a measure of well-to-wheels greenhouse gas production. The well-to-wheels carbon intensity of ethanol does not include its chemical carbon content because it arises from a renewable source, but does consider all upstream farming, production, and transportation carbon impacts. The well-to-wheels carbon intensity of the petroleum fraction includes the chemically bound carbon, as well as production and transportation impact. Carbon intensity modeling results for ethanol vary widely, primarily due to differences in land-use change assessment. The GREET model has gained wide acceptance and provides a present-day carbon intensity for pure ethanol that is 43% lower than for petroleum gasoline. Ethanol exhibits a high blending octane number so that the petroleum component has a lower octane rating than required for purely petroleum gasoline. Fuel trends and modeling suggest that a 10% (by volume) ethanol addition enables a 9% reduction of aromatics, which have a high carbon intensity. If the carbon reduction benefits of the aromatic reduction are assigned to the agency of the ethanol, the blending carbon intensity of ethanol is 56% lower than for petroleum gasoline. Increase in ethanol blending therefore offers substantial immediate climate change reduction.
混合汽油中乙醇的碳强度
减少轻型运输车队的温室气体排放迫在眉睫,需要同时解决电动和传统动力总成技术的问题。内燃机将继续用于车辆推进,车队周转缓慢,鼓励减少汽油中的碳含量。目前,乙醇是一种可再生燃料,以10%的比例与石油混合,以生产成品市场汽油。乙醇使低碳的石油混合物成分,提供额外的减少,但这在研究中经常被忽视。碳强度,以CO<sub>2</sub>燃烧时释放的热量与质量之比,是衡量从油井到车轮的温室气体产量的指标。乙醇从油井到车轮的碳强度不包括其化学碳含量,因为它来自可再生能源,但它考虑了所有上游农业、生产和运输的碳影响。石油馏分的井到轮的碳强度包括化学结合的碳,以及生产和运输的影响。乙醇的碳强度模拟结果差异很大,主要是由于土地利用变化评估的差异。GREET模型已被广泛接受,并为纯乙醇提供了目前的碳强度,比石油汽油低43%。乙醇表现出较高的混合辛烷值,因此石油成分的辛烷值比纯石油汽油所需的辛烷值低。燃料趋势和模型表明,添加10%(按体积计算)的乙醇可使具有高碳强度的芳烃减少9%。如果将芳香还原的碳减排效益分配给乙醇的代理,则乙醇的调和碳强度比石油汽油低56%。因此,增加乙醇混合可以立即大幅减少气候变化。
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来源期刊
SAE International Journal of Fuels and Lubricants
SAE International Journal of Fuels and Lubricants TRANSPORTATION SCIENCE & TECHNOLOGY-
CiteScore
2.20
自引率
10.00%
发文量
16
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