by Jordan Wilkerson
figures by Brad Wierbowski
The Environmental Protection Agency (EPA) recently issued a new wave of regulations, and they focus on one thing: methane. Due to the EPA’s recent proposal, we have been inundated with stories about methane, its connection to the fossil fuel industry, and its comparison to carbon dioxide as a greenhouse gas [1,2]. However, the authors often leave out a scientific explanation, instead, placing the focus on potential economic consequences. Even so, it is still important to understand both the scientific and social justifications behind why regulations to reduce methane emissions are being imposed on natural gas and oil companies.
How is Methane Escaping?
Natural gas production has increased the release of methane into the atmosphere. The majority of natural gas is methane (chemical structure in Figure 1), so natural gas leaks and methane leaks are essentially synonymous. In extracting and transporting natural gas, potential leaks abound throughout the entire process, starting with the wellhead itself. At a well site, natural gas is siphoned from deep underground and sent through a pipe system to be stored or distributed for use at a power plant. Pressure gauges within the wellhead monitor whether the pressure is too high to safely operate the machinery. When these gauges read too high, the wellhead is vented to reduce pressure, releasing a puff of methane in the process. It is possible to reduce methane release by burning the methane so carbon dioxide is released instead. To those involved in the natural gas industry, this is known as flaring. However, this is not always done and is only feasible if workers can anticipate the plume of methane in advance .
In many cases, natural gas is not released intentionally, but rather because the plumbing doesn’t quite work the way we want it to. Pressure gauges and other wellhead components inevitably become leaky, leading to small amounts of natural gas seeping out in various locations. This is more cumbersome to address, as each component must be constantly monitored to assess for a potential, new leak. No individual leak is necessarily significant, so identifying a single leak is does not meaningfully reduce the amount of methane released. However, these leaks collectively add up to a sizable loss of natural gas into the atmosphere, especially when you consider that the pipelines transporting the natural gas to the power plants and storage facilities will inevitably developing leaks all throughout their length (Figure 2) .
Fracking Causes Additional Leakage
When gas wells are hydraulically fractured, an additional methane plume is released. This relates to the “hydraulic” component of hydraulic fracturing. After a well is drilled, the workers create controlled explosions to form cracks that branch away from the main hole. Water is then forced into the well: the granules of sand found in the water lodge into the cracks formed from the explosions and prevents them from resealing (see SITN’s video covering hydraulic fracturing for more detail ). These additional cracks cause more natural gas to escape from hydraulically fractured wells. However, at this depth, the water is at a much higher pressure than it normally would be at the surface. When water is at a higher pressure, it is better able to dissolve gases; this includes methane. Therefore, a side effect of this technique is that some methane is dissolved into the water and released when the water returns to the surface (Figure 2).
To appreciate why this process results in methane release, consider a bottle of soda. The bottle of soda has carbon dioxide dissolved in it – making it carbonated. However, when we open the bottle, we hear an audible fizz. What happened? We lowered the pressure by opening the bottle. When the pressure decreases, the beverage cannot hold as much carbon dioxide, so the gas fizzes out. Similarly, when we force water into these drill sites, more methane dissolves than would happen under normal pressure. Therefore, when we bring the water back up to the surface, methane plumes out, as the water can no longer retain it.
As of June 2013, 40% of the total natural gas extracted in the U.S. came from hydraulically fractured wells . While it remains unclear how much methane is being released from natural gas development sites, many scientific reports estimate that the percentage of natural gas lost in the production/distribution process approaches 8% for hydraulically fractured wells . This certainly justifies trying to reduce methane emissions if the gas is detrimental to us, and we have known for a while that it is. But why?
Methane: the Other Greenhouse Gas
Methane is 25 times better than carbon dioxide at trapping heat in our atmosphere. Although this number has appeared in countless headlines [1,2], the most recent number is even higher: 34 . What does it mean, though? This number is known as a Global Warming Potential (GWP), a statistic given to every greenhouse gas that refers to the amount of heat trapped by a gas compared to carbon dioxide over a certain period of time. This means that the GWP over 20 years will not necessarily be the same as the GWP over 100 years. The value 34 refers to a 100-year timescale. However, over 20 years, methane has a GWP of 86: this means that methane is a much more potent greenhouse gas than carbon dioxide, but it also does not remain in the atmosphere for as long (Figure 3).
Therefore, while methane drastically increases the rate of warming, reducing methane emissions could cause a comparatively quick reversal. Unfortunately, it is unlikely to be this simple: drastic temperature increases can cause irreversible damage, with the increased rate of melting polar ice as one example. Anyone from Alaska can tell you of the infrastructural damage caused due to the melting of the frozen soil many houses and buildings rest on . Methane concentrations in our atmosphere might quickly respond to reducing emissions, but the greenhouse gas can cause damage that will not be easily reversed.
The Other Side of Methane
Methane is more than just a greenhouse gas; it is also a precursor to urban pollutants. As mentioned earlier, methane remains in the atmosphere for a much shorter time than carbon dioxide. It doesn’t just disappear, though: it reacts with other gases in the atmosphere to form new chemicals. This results in the production of volatile organic compounds and ozone ; these chemicals are toxic resulting in maladies such as chest pains, breathing problems, and cancer (Figure 3) . Eventually, methane is oxidized to carbon dioxide, so after methane goes through all of these chemical reactions that produce insidious compounds, its final product is still a greenhouse gas, albeit a less potent one.
While carbon dioxide is certainly the primary greenhouse gas, methane is still a chemical that can exacerbate urban pollution and cause serious health risks. Compared to carbon dioxide, methane is more manageable to reduce: carbon dioxide is an inevitable product of fossil fuel combustion, while industrial methane is largely released to the atmosphere on accident. Therefore, it is theoretically possible to rely on fossil fuels without emitting methane. While there may be legal hurdles, and industries might consider the regulations on methane emissions unnecessary, one thing remains true: working to reduce how much methane we send into our atmosphere just makes sense.
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