Life Cycle Greenhouse Gas Emissions From US Liquefied Natural Gas Exports: Implications for End Uses
Life Cycle Greenhouse Gas Emissions From US Liquefied Natural Gas Exports: Implications for End Uses
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DOI：
10.1021/es505617p
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发表时间：
2015-03-03
影响因子：
11.4
通讯作者：
Matthews, H. Scott
中科院分区：
文献类型：
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作者：
Abrahams, Leslie S.;Samaras, Constantine;Matthews, H. Scott
本研究分析了美国液化天然气 (LNG) 出口增量如何影响全球温室气体 (GHG) 排放。我们发现，美国出口的液化天然气在欧洲和亚洲再气化时，平均燃烧前排放量为 37 克二氧化碳当量/MJ。从美国港口出口到亚洲和欧洲市场的液化天然气的运输排放量仅占燃烧前生命周期排放量的3.5-5.5%，因此运输距离不是温室气体的主要驱动因素。针对潜在最终用途（电力和工业供暖）和现有燃料（煤炭和俄罗斯天然气）替代如何影响温室气体排放的基于情景的分析表明，使用美国出口液化天然气发电的平均排放量为 655 克二氧化碳当量/千瓦时（90% 置信区间为 562770），比美国天然气发电增加了 11%。工业供暖的平均排放量为 104 克二氧化碳当量/MJ (90% CI: 87123)。通过替代煤炭，液化天然气每千瓦时电力可节省 550 克二氧化碳当量，每兆焦热量可节省 20 克二氧化碳当量。在上游电力和供暖无组织排放率下，液化天然气可分别节省高达 9% 和 5% 的温室气体。只要美国的无组织排放率保持在俄罗斯天然气的 57% 估计以下，无论全球升温潜能值如何，如果俄罗斯管道天然气被取代用于电力和供暖，温室气体就会减少。然而，从具体国家碳核算的角度来看，应计社会成本和效益存在不平衡。假设碳的平均社会成本为 49 美元/吨，美国液化天然气替代煤炭发电的全球平均节省额为每千立方英尺 (Mcf) 以液化天然气形式出口的气态天然气 (0.028 美元/千瓦时) 1.50 美元。相反，美国出口液化天然气的碳成本为 1.80 美元/Mcf（0.013 美元/kWh），或在潜在贴现率范围内为 0.50-5.50 美元/Mcf。在液化天然气出口的国家利益估算中，考虑到隐含碳排放的空间变化非常重要。
This study analyzes how incremental U.S. liquefied natural gas (LNG) exports affect global greenhouse gas (GHG) emissions. We find that exported U.S. LNG has mean precombustion emissions of 37 g CO2-equiv/MJ when regasified in Europe and Asia. Shipping emissions of LNG exported from U.S. ports to Asian and European markets account for only 3.5-5.5% of precombustion life cycle emissions, hence shipping distance is not a major driver of GHGs. A scenario-based analysis addressing how potential end uses (electricity and industrial heating) and displacement of existing fuels (coal and Russian natural gas) affect GHG emissions shows the mean emissions for electricity generation using U.S. exported LNG were 655 g CO2-equiv/kWh (with a 90% confidence interval of 562770), an 11% increase over U.S. natural gas electricity generation. Mean emissions from industrial heating were 104 g CO2-equiv/MJ (90% CI: 87123). By displacing coal, LNG saves 550 g CO2-equiv per kWh of electricity and 20 g per MJ of heat. LNG saves GHGs under upstream fugitive emissions rates up to 9% and 5% for electricity and heating, respectively. GHG reductions were found if Russian pipeline natural gas was displaced for electricity and heating use regardless of GWP, as long as U.S. fugitive emission rates remain below the estimated 57% rate of Russian gas. However, from a country specific carbon accounting perspective, there is an imbalance in accrued social costs and benefits. Assuming a mean social cost of carbon of $49/metric ton, mean global savings from U.S. LNG displacement of coal for electricity generation are $1.50 per thousand cubic feet (Mcf) of gaseous natural gas exported as LNG ($.028/kWh). Conversely, the U.S. carbon cost of exporting the LNG is $1.80/Mcf ($.013/kWh), or $0.50-$5.50/Mcf across the range of potential discount rates. This spatial shift in embodied carbon emissions is important to consider in national interest estimates for LNG exports.