The argument goes something like this: natural gas is the cleanest fossil fuel. When burned, it produces 50% less CO2 than coal, and 25% less CO2 than petrol. By choosing to fuel our homes, our power plants, and even our means of transport with natural gas, we are making a responsible choice that will help to slow the warming of our climate.
But there is a problem with this story. During the production, distribution and consumption of natural gas, small quantities of methane leak out into the atmosphere. These are known as fugitive emissions. The reason they are such a problem is that methane is itself a greenhouse gas – and a far more potent one than CO2. The IEA estimates that over a hundred year period, each tonne of methane released into the atmosphere warms the climate to an extent equivalent to between 28 and 36 tonnes of CO2.
That means that simply looking at the CO2 emissions from the combustion of different fuel types is not good enough. To get a clearer picture of how climate friendly an option natural gas really is, we first need to understand how much methane escapes into the atmosphere as a result of its use. According to a study published in the journal of the National Academy of Sciences, the logic of natural gas as a climate friendly fuel begins to break down if the total level of fugitive emissions rises above 3.2%. Beyond this point, the authors of the study argue, we’d be no worse off burning coal.
A Paucity of Data
So how does natural gas measure up, when you take fugitive emissions into account? The difficulty is that it’s pretty hard to tell how much methane is actually being released by natural gas systems. This isn’t because the data on atmospheric methane concentrations is in any way unclear – levels have risen from 1570 parts per billion in the early 1980’s, to approximately 1850 parts per billion in the present day. But only a fraction of atmospheric methane will have come from the natural gas industry.
There are in fact a variety of different sources of methane emissions, many of them unrelated to human activity. Emissions from wetlands alone account for 31% of the total, according to Global Carbon Project figures. Once natural sources of methane emissions have been eliminated, the remaining anthropogenic methane emissions need to be disaggregated into different sectors and sources. Depending on which region you look at, and whose figures you go by, these proportions can vary widely.
The EPA’s estimate for the U.S. is that natural gas systems account for 24% of the country’s total anthropogenic methane emissions. By contrast, agriculture accounts for 37% and waste accounts for 20%. Significantly, coal mining is also a major offender, accounting for 10%. But such figures are far from exact, and often contradictory. Speaking at the Flame conference in May, Tim Gould of the IEA’s World Energy Outlook division was brutally honest in his assessment of the available information: “the baseline data is pretty poor.”
A different approach is to try to measure emissions as they happen. The EPA’s ‘Inventory of U.S. Greenhouse Gas Emissions and Sinks’ estimates that of the total methane emissions released by natural gas systems, 40% come from venting – i.e. the intentional release of excess or low quality gas into the atmosphere – while 60% are from fugitive emissions. But accurately pinpointing where leakages occur, and how much gas is released, is complicated by the sheer extent of natural gas infrastructure. It is difficult to generalise measurements from a single wellhead or stretch of pipeline to a larger system in which different production techniques, inconsistent monitoring standards and variations in infrastructural integrity can all affect the quantities of methane released.
The result is that there is little consensus about the true scale of the problem. A useful report by Carbon Brief shows the discrepancies between some of the estimates given by studies on the subject. The good news is that although there are some estimates which come in at above the crucial 3.2% threshold, they are definite outliers. But that doesn’t mean the industry should tolerate any complacency on fugitive emissions. “Even if natural gas is always better than coal,” Tim Gould told the Flame conference, “simply comparing gas to the most emissions intensive fuel is setting the bar far too low.”
Setting the Bar Higher
So what can be done to set the bar higher? Investment in better monitoring technologies is one part of the solution. Earlier this year, the Environmental Defence Fund announced that it would be developing a satellite with the sole task of measuring methane emissions around the world. The satellite will be launched in 2021, and will be able to provide high quality data on the emissions intensity of oil and gas producing regions. Discovering where methane leakage is most prevalent should help the industry to focus its efforts on countering the problem.
On a more granular level, better monitoring also needs to be applied to individual production sites, particularly those nearing the end of their lifecycles. A 2013 University of Texas at Austin study focused on emissions from Liquid Unloadings and Pneumatic Controllers used in the production of shale gas found that a small proportion of wells account for the majority of methane emissions from fracking. A key conclusion of the study was that older wells, in which liquid unloadings are needed more often to maintain the flow of natural gas, are far more prone to emissions.
Another step participants in the industry can take is to make the case that reducing methane emissions doesn’t have to be expensive. In fact, it doesn’t have to cost anything at all, up to a point. According to the IEA, the costs of preventing 40% - 50% of current emissions wold be offset by the value of the gas that would thereby be retained in the system. The climate impact of eliminating these emissions would be equivalent to emitting “160 billion fewer tonnes of CO2 over the rest of the century”.
Finally, the industry can’t afford to wait around for regulators to agree on solutions before taking action on the issue. There are some encouraging signs that this is understood by industry leaders. Last year ExxonMobil committed to a plan for reducing methane emissions from its shale gas subsidiary, XTO Energy, despite attempts by the Trump administration to roll back Obama-era regulations on methane emissions.
Likewise, in a recent interview with KNect365 Energy (extracts of which can be found in our industry review paper, here) Timm Kehler, CEO of German natural gas initiative Zukunft ERDGAS, told us that a will exists within the industry to combat the problem. “Overall, our findings show that increased awareness about the topic, as well as state-of-the-art infrastructure technology, can further help to reduce methane leakage in the gas industry,” he said.
