The global pursuit of climate goals has laid out a clear mandate for the future of coal – a complete phase-out by 2040, a necessary step to mitigate the most severe consequences of global warming. As coal’s decline takes center stage, natural gas has often been hailed as a transitional energy source, bridging the gap between coal and renewable alternatives. However, a recent study has cast doubt on this narrative, suggesting that natural gas might carry a climate impact comparable to the fossil fuel it seeks to replace.
Despite the connotations of being a cleaner and healthier energy choice than coal or oil, the term “natural gas” can be misleading. This fuel, too, falls within the fossil fuel category and is predominantly composed of methane, a greenhouse gas with a potency far surpassing that of carbon dioxide – a gas emitted from coal combustion. Furthermore, as methane is extracted from beneath the Earth’s surface and transported to power plants or residences for electricity generation or heating, it is prone to leakage.
The intricacies of the net climate impact of gas and coal life-cycle emissions are intricately linked to the phenomenon of methane leakage. Each molecule of methane that escapes into the atmosphere alters the perceived climate benefits of natural gas, given its significant warming effect over its lifespan compared to CO2. This leads to the pivotal finding of the Gordon et al. study: global gas systems experiencing methane leaks exceeding 4.7% over a 20-year timeframe or 7.6% over a century are comparable in their climate impact to the life-cycle emissions of coal resulting from methane leaks in coal mines.
However, the equation is not solely determined by methane. The net climate impact of coal is also influenced by sulfur dioxide (SO2) emissions, which give rise to sulfate aerosols that mask warming effects. To comprehensively analyze the interplay between natural gas and coal emissions, the study constructs scenarios that combine varying methane leakage rates from both sources with a spectrum of SO2 emissions based on coal sulfur content, flue gas scrubber efficiency, and sulfate aerosol global warming potentials. The interjection of methane and SO2 alongside CO2 alters the emissions balance between natural gas and coal.
Interestingly, the study posits that even a gas system leakage rate as low as 0.2% can result in parity with coal, assuming the coal in question contains 1.5% sulfur and is subjected to a 90% efficient scrubbing process, and no methane is leaked from coal mines. This underscores the sensitivity of the comparison to specific parameters and conditions.
The urgency to address methane emissions gains substantial support from recent aerial measurements across US oil and gas production basins. These surveys have unveiled natural gas leak rates from 0.65% to 66.2%. Such variations highlight the global scale of the problem, underscoring the imperative to accelerate practices related to methane emissions detection, accounting, and management.
Policymakers, energy leaders, and environmental advocates must weigh the potential benefits of natural gas against the inherent risks associated with methane leakage. Our choices on the energy front have far-reaching consequences, and the pathway to a sustainable future requires a comprehensive and nuanced assessment of all available options.
Writing by Moe Khaled; Editing by Sarah White