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Caldeira Lab

Key Factors for Assessing Climate Benefits of Natural Gas Versus Coal Electricity Generation, Xiaochun Zhang

[Environmental Research Letters]

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Transcript

Some people consider natural gas as a “bridge” fuel to a lower carbon energy system, because burning natural gas emits less CO2 than coal. However, potential climate benefits of natural gas use could be offset by methane leakage. So there are two questions: what are key factors affecting the relative merits of natural gas versus coal power plants, and when is natural gas better than coal.

We developed a simple model, and applied it to harmonized life-cycle datasets, to estimate carbon dioxide and methane emissions from power plants, and resulting global warming.

We identified power plant efficiency and methane leakage as the key factors affecting the relative merits of natural gas versus coal. We found that, during the plant operation, if there is substantial methane leakage, natural gas plants can produce greater near-term warming than coal plants with the same power output. However, if the methane leakage is low and the plant efficiency is high, natural gas plants can produce some reduction in near-term warming. In any case, without carbon capture and storage, natural gas plants cannot achieve deep reductions that would be needed to avoid additional global warming.

Let’s say you are faced with retiring a typical coal power plant and replacing with a natural gas power plant. If the natural gas power plant has a typical efficiency, the methane leakage would need to be below 2% to keep it from causing more near term warming than the coal plant. However, if the coal plant is replaced by the best natural gas plant, methane leakage could be up to 4% or 5% without causing more near term warming than the coal plant. Thanks for listening.


Zhang, X., N. P. Myhrvold, and K. Caldeira, 2014: Key factors for assessing climate benefits of natural gas versus coal electricity generation. Environ. Res. Lett., 9, 114022, doi:10.1088/1748-9326/9/11/114022.


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