When natural gas is a climate friend and when it’s a foe

Natural gas is often called the cleanest fossil fuel. It produces about 30 percent and 44 percent less carbon dioxide than oil and coal, respectively, for the same energy. Another thing that sets it apart from oil and coal is its common use for both power generation and transportation as compressed natural gas (CNG).

To take the most advantage of this relatively clean-burning fossil fuel to reduce carbon emissions, it should be used for power and heat rather than burnt in vehicles, Rice University researchers say.

Civil and environmental engineers Daniel Cohan and Shayak Sengupta calculated the greenhouse gas emissions that would be saved when swapping other fuels with natural gas in vehicles, furnaces, and power plants. They found that the highest savings—more than 50 percent—would come from replacing old coal-fired plants with gas-fired ones. Switching old heating oil furnaces for new natural gas ones also significantly cuts emissions. But contrary to the industry’s push for clean CNG vehicles, they give the least benefit, essentially matching the emissions of modern gasoline or diesel engines. The results are published in the International Journal of Global Warming.

The researchers used the best available data and models to calculate emissions at every step of a fuel’s lifecycle, from production and transport through its use when burnt. They also included methane leaks. They compared emissions for substituting natural gas in five places: coal for electricity generation, oil for home heating furnaces, gasoline in light-duty cars, diesel in transit buses, and exports to Japan for electricity generation.

Cohan and Sengupta worked on this analysis in 2012 and 2013, and energy markets have transformed in the two years it took for the paper to get published. Increased natural gas production has driven prices to a historic low. Solar and wind prices are also falling rapidly. And hybrid and electric vehicles are gaining popularity.

Given this, Cohan writes in a recent blog post that the question they posed might be less relevant now. Instead of looking at swapping natural gas for other fossil fuels, he might investigate its interplay with alternative energy sources.

A battleground has emerged between natural gas and renewables, he says. “Is natural gas serving as a rapid off-ramp from coal and oil, bridging toward the renewables-led future that climate scientists deem necessary to avert catastrophic climate change? Or has natural gas become a barrier, competing with renewables as replacements for coal and oil?” – Prachi Patel | 10 March 2016

Source: Daniel S. Cohan and Shayak Sengupta (2016). Net greenhouse gas emissions savings from natural gas substitutions in vehicles, furnaces, and power plants. Int. J. of Global Warming doi: 10.1504/IJGW.2016.074960

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