Global methane emissions from natural gas transmission and distribution networks

Given the significant global warming power and short atmospheric lifetime of methane, one of the most effective mitigation strategies for limiting global warming over the short term is to target the anthropogenic sources of methane and rapidly reduce their emissions. Tracking gas network input and output data shows that more natural gas enters the transmission and distribution networks than leaves: this difference is called unaccounted-for gas. The aim of this article is to investigate the possibility of losses, mostly leaks, along natural gas transmission and distribution networks and to quantify them. These leaks amount to methane emissions since natural gas is mainly composed of methane, and methane has a greater warming power than CO2. This paper examines the sources and quantities of unaccounted-for gas and evaluates the resulting methane emissions. First, various data monitored along networks are collected and used to assess the unaccounted-for gas per country. We showed that the average unaccounted-for gas per country was 1.7% in 2021 but with significant disparities between regions, ranging from 0.01% to 15%. Second, the obtained unaccounted-for gas values can be used as a proxy to approximate the quantities of methane released into the atmosphere by natural gas networks. We calculated that a total of 18 million tons (Mt) of methane were emitted in 2021. The main producing countries present high unaccounted-for gas volumes and methane emissions, which can be explained by the aging of their gas networks. Conversely, networks in more recent markets or advanced countries have fewer leaks, leading to more moderate methane emissions. This shows that methane emissions can be reduced in well-maintained networks. The accounting method developed in this article would make it possible to verify the emissions reductions announced for gas networks in the future if repeated over time.