Environmentalists have made no bones about what they blame for the trend of rising global methane emissions. The Environmental Defense Fund (EDF) has hyperbolically characterized the environmental impact of methane emissions from the oil and natural gas industry as “staggering,” while the U.S. Environmental Protection Agency’s (EPA) has pushed its costly new regulations as a solution that is absolutely necessary to “combat climate change.”
But as environmentalists and the EPA continue to focus all their attention on methane emissions from oil and natural gas systems, study after study has found this tired narrative is indeed a methane myth.
Instead, recent studies find that microbial sources such as wetlands, agriculture, rice paddies and even man-made reservoirs are the reason a rise in global methane emissions in recent years. Let’s have a look at a few of them.
Washington State University-Vancouver Study on Methane from Man-Made Reservoirs
This study found that man-made reservoirs used primarily for hydroelectric power — long touted as a “clean” alternative to fossil fuel electrical generation — emit as much methane as world’s rice paddies, which have been estimated to be more than 700 million metric tons, or 10-12 percent of the world’s total anthropogenic emissions! As study co-authors John Harrison and Bridget Deemer told Climate Central in an email:
“To put these reservoir methane emissions in context, they are similar in size to other major human sources such as biomass burning and rice paddies, hence reservoirs are not necessarily the ‘clean’ energy source they are often thought to be.”
The researchers found man-made reservoirs are responsible for 1.3 percent of total global greenhouse gas emissions, with a vast majority of that total being methane. From the study:
“Specifically, this work highlights the dominant contribution of CH4 emissions to total reservoir carbon emissions…
“Our synthesis confirms that CH4 emissions are responsible for the majority of the radiative forcing from reservoir water surfaces (approximately 80% over the 100-year timescale and 90% over the arguably more policy-relevant 20-year timescale) and that modeling approaches that ignore ebullitive CH4 flux may fail to accurately quantify the magnitude of fluxes.”
The study also explains why man-made reservoirs are a major (albeit overlooked) GHG emission source:
“Artificial reservoirs created by dams are distinct from natural systems in a number of key ways that may enhance GHG emissions from these systems. First, the flooding of large stocks of terrestrial organic matter may fuel microbial decomposition, converting the organic matter stored in above and below ground biomass to carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Second, reservoirs often experience greater fluctuations in water level than natural lakes. Drops in hydrostatic pressure during water level drawdowns can enhance CH4 bubbling (e.g., ebullition) rates at least over the short term (Maeck et al. 2014). This enhanced ebullition may then decrease the fraction of CH4 that is oxidized to CO2, a less potent GHG, by methane oxidizing microbes (Kiene 1991). Finally, the high catchment area–to–surface area ratios and close proximity to human activities (Thornton et al. 1990) characteristic of many reservoirs are likely to increase the delivery of organic matter and nutrients from land to water (relative to natural lakes), potentially fueling additional decomposition.”
In fact, the study found that 79 percent of carbon dioxide equivalent emissions from reservoirs are methane, which is 25 percent higher than previously thought
For perspective, based on this study and EPA methane emissions estimates, EID research indicates man-made reservoirs emit nearly three times more methane annually than U.S. oil and natural gas systems (244.2 mmt, according to the latest EPA GHG Inventory).
Interestingly, as EPA continues to push on with its methane regulations of the oil and gas industry, methane emissions from man-made reservoirs aren’t even taken into account by the agency, as the following EPA pie chart shows.
Despite the fact that EPA does not categorize methane emissions from man-made reservoirs separately in its current inventories, scientists have known for some time that reservoirs are a major sources of emissions.
A 2012 study actually indicated that methane emissions from reservoirs are right on par with those from global oil and natural gas systems. That study found all large reservoirs globally could emit up to 104 teragrams of methane annually. By comparison, NASA estimates that global methane emissions associated with burning fossil fuels totals between 80 and 120 teragrams annually.
In this latest study, researchers analyzed more than 100 studies on 267 reservoirs worldwide. They found that reservoirs emit just shy of 1 billion metric tons CO2 eq. greenhouse gas emissions annually, which exceeds Canada’s annual GHG emissions. And those totals are expected to increase, considering there are 847 large hydroelectric dam projects in the works.
National Oceanic and Atmospheric Administration (NOAA) Study
This study found that microbial sources such as rice paddies and wetlands are the cause of the global increase in methane emissions. Lead author Stefan Schwietzke of NOAA at the University of Colorado Boulder also emphasized that fossil fuel development is “not responsible for the increase in total methane emissions observed since 2007.”
And despite what some headlines may have suggested, the researchers’ data show methane emissions from fossil fuel production are “not increasing over time” even though energy production has dramatically increased. From the study:
“[T]his study does not confirm an upward trend of FF emissions in global CH4 inventories despite the large increase in natural gas, oil and coal production and use over the past three decades.”
The researchers made their determinations by using isotopic analysis to show that natural or microbial sources, such as “wetlands, ruminants, rice, landfill/waste, termites” are the source of most of the methane released to the atmosphere each year.
The study’s headline and some of the news outlet headlines highlighted the fact that the researchers found methane emissions from fossil fuel development were 20 to 60 percent higher than what previous estimates found. But the key phrase here is “fossil fuels” because the researchers evaluated the contribution of all fossil fuels and even natural seeps together, without determining how much is coming from each source, to make these claims. From the report:
“We find that total fossil fuel methane emissions (fossil fuel industry plus natural geological seepage) are not increasing over time, but are 60 to 110 per cent greater than current estimates owing to large revisions in isotope source signatures. We show that this is consistent with the observed global latitudinal methane gradient. After accounting for natural geological methane seepage, we find that methane emissions from natural gas, oil and coal production and their usage are 20 to 60 per cent greater than inventories.” (emphasis added)
When they do actually single out natural gas emissions, the researchers are very clear that leakage rates are down significantly, crediting “industry improvements”:
“[W]e also find that methane emissions from natural gas as a fraction of production have declined from approximately 8 per cent to approximately 2 per cent over the past three decades.”
Department of Earth Sciences at Royal Holloway, University of London Study
“Our results go against conventional thinking that the recent increase in atmospheric methane must be caused by increased emissions from natural gas, oil, and coal production. Our analysis of methane’s isotopic composition clearly points to increased emissions from microbial sources, such as wetlands or agriculture.”
The study states plainly that its data found “both the majority of this methane increase and the isotopic shift are biogenic,” and the authors noted that both studies’ findings “contradict emission inventories.”
Using measurements made by NOAA’s Cooperative Global Air Sampling Network in three locations (the Canadian Artic, the south Atlantic and South Africa), a combination of latitudinal analysis and isotopic data led researchers to determine a majority of the methane increase since 2007 has a biogenic signature, meaning it cannot be attributed to thermogenic methane from oil and gas development.
The study further notes that the tropical wetlands are responsible for as much as a quarter of global methane emissions, and that significant weather events — such as La Nina in 2007 and 2008 — could explain a nearly 50 percent hike in methane emissions when compared to the last half decade.
NOAA and the National Institute of Water and Atmospheric Research in New Zealand (NIWAR) Study
This study also found increased global methane emissions are coming from wetlands and agriculture.
On the increase in agriculture, the study itself notes that India, China and South East Asia are likely emitting the highest amounts of methane: “India and China’s dominance in livestock-emissions and S.E. Asian rice cultivation are consistent with the location of the source increase.”
Climatewire further reported,
“Greenhouse gas inventories from U.S. EPA show that emissions from fossil fuel extraction have increased in recent years. But this has apparently not registered on the global scale. This is possibly because the U.S. energy industry contributes little to the overall burden of global fossil fuel emissions, Schaefer said.” (emphasis added)
Like the University of London study, the researchers used a fingerprinting technique that evaluates thermogenic methane associated with oil and natural gas development, as well as biogenic methane associated with natural or agricultural causes. The researchers found that thermogenic methane did not increase, even during the oil and natural gas boom.
All This Considered, Why Are the EPA’s Methane Rules Necessary?
The fact that these studies have found increases global methane emissions are not being driven by oil and natural gas production should really come as no surprise, considering methane emissions from oil and natural gas systems continue to decrease at the same time production skyrockets thanks to hydraulic fracturing.
In fact, since 1990, U.S. natural gas production has increased 70 percent, while the economy has grown 75 percent and methane emissions from natural gas systems have declined 15 percent.
As the following Global Methane Initiative chart shows (based on 2010 data, the latest available), methane emissions from oil and natural gas development are an ever-declining piece of a very big anthropogenic methane emissions pie that has numerous slices.
Considering the aforementioned research estimates man-made reservoirs and wetlands could account for a combined 36 percent of total global methane emissions to go along with all these man-made sources, it is really no wonder EID research has found the EPA’s methane rule would account for a reduction of a mere 0.0047 degrees Celsius – or four one-thousandths of one degree – by the year 2100.
In other words, the regulations would have virtually no impact on the climate.
Which begs the question: if environmentalists’ goal truly is fighting climate change, why are they focusing all their attention on fracking?