The critical role of natural gas in the transition to clean energy, A new MIT study examines the opposing roles of natural gas in the battle against climate change as a bridge toward a lower-emissions future, but also a contributor to greenhouse gas emissions.

Natural gas in the transition to clean energy , which is mostly methane, is viewed as a significant bridge fuel to help the world move away from the greenhouse gas emissions of fossil fuels, since burning natural gas for electricity produces about half as much carbon dioxide as burning coal.

But methane is itself a potent greenhouse gas, and it currently leaks from production wells, storage tanks, pipelines, and urban distribution pipes for natural gas.

This uncertainty adds to the difficulty of assessing natural gas’ role as a bridge to a net-zero-carbon energy system, and in knowing when to transition away from it. But strategic choices must be made now about whether to invest in natural gas infrastructure.

This inspired MIT researchers to quantify timelines for cleaning up natural gas infrastructure in the United States or accelerating a shift away from it, while recognizing the uncertainty about fugitive methane emissions.

The study shows that in order for natural gas to be a major component of the nation’s effort to meet greenhouse gas reduction targets over the coming decade, present methods of controlling methane leakage would have to improve by anywhere from 30 to 90 percent.

Given current difficulties in monitoring methane, achieving those levels of reduction may be a challenge. Methane is a valuable commodity, and therefore companies producing, storing, and distributing it already have some incentive to minimize its losses. However, despite this, even intentional natural gas venting and flaring (emitting carbon dioxide) continues.

The study also finds policies that favor moving directly to carbon-free power sources, such as wind, solar, and nuclear, could meet the emissions targets without requiring such improvements in leakage mitigation, even though natural gas use would still be a significant part of the energy mix.

The researchers compared several different scenarios for curbing methane from the electric generation system in order to meet a target for 2030 of a 32 percent cut in carbon dioxide-equivalent emissions relative to 2005 levels, which is consistent with past U.S. commitments to mitigate climate change.

The actual leakage rates associated with the use of methane are widely distributed, highly variable, and very hard to pin down. Using figures from a variety of sources, the researchers found the overall range to be somewhere between 1.5 percent and 4.9 percent of the amount of gas produced and distributed.

The researchers looked at the whole range of uncertainties, from how much methane is escaping to how to characterize its climate impacts, under a variety of different scenarios. One approach places strong emphasis on replacing coal-fired plants with natural gas, for example; others increase investment in zero-carbon sources while still maintaining a role for natural gas.

In the first approach, methane emissions from the U.S. power sector would need to be reduced by 30 to 90 percent from today’s levels by 2030, along with a 20 percent reduction in carbon dioxide. Alternatively, that target could be met through even greater carbon dioxide reductions, such as through faster expansion of low-carbon electricity, without requiring any reductions in natural gas leakage rates.

One question raised by the study is how much to invest in developing technologies and infrastructure for safely expanding natural gas use, given the difficulties in measuring and mitigating methane emissions.

The detailed analysis in this study should provide guidance for local and regional regulators as well as policymakers all the way to federal agencies, they say. The insights also apply to other economies relying on natural gas.

The best choices and exact timelines are likely to vary depending on local circumstances, but the study frames the issue by examining a variety of possibilities that include the extremes in both directions that is, toward investing mostly in improving the natural gas infrastructure while expanding its use, or accelerating a move away from it.

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