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Circuit Breakers

Debunking electrification myths

February 28, 2023

Decarbonizing buildings with “renewable natural gas” doesn’t stand up to scrutiny, and is a distraction from our clean electric future.

Sam Calisch

Rewiring America

Focus points:

“Renewable natural gas” is often proposed as a way to meet climate targets while still investing in fossil fuel infrastructure.
Research shows that when methane leaks are accounted for, renewable natural gas actually emits just as much as fossil natural gas.
The available supply of renewable natural gas is tiny, with current production at just 0.2 percent of U.S. gas consumption and maximum technical potential at only 1.3 percent.
Heating with fossil natural gas is already more expensive than electric heat pumps in many places, and renewable natural gas is two to fifteen times more expensive than this.
In contrast, electrification is ready to deploy today at scale, actually reduces emissions, saves money, and avoids the harmful health impacts of burning gas in our homes.

“Renewable natural gas” (RNG) [1] is frequently proposed as a get-out-of-jail-free card for building decarbonization [2]. As the story goes, we can use the same furnaces and boilers, the same meters, the same piped distribution network—we’ll just replace the fossil natural gas inside with a climate-friendly alternative to make the whole system clean [3]. Unfortunately, this tempting proposition just doesn’t stand up to scrutiny, nor does it deliver the benefits that electrification does.

Renewable natural gas is chemically similar to the fossil natural gas used in furnaces today [4], but is derived from present-day organic sources (like agriculture, landfills, wastewater, and manure) instead of the prehistoric ones that created fossil fuels. Because these sources pulled carbon out of the atmosphere recently, proponents say that re-releasing that same carbon by burning the gas won’t increase overall emissions. What’s more, they say since the contained methane is a more potent greenhouse gas than carbon dioxide, burning it directly actually reduces emissions. If that sounds like a load of manure to you, you’re right.

The first claim, that renewable natural gas eliminates the emissions of the fossil natural gas we currently use, is false because, no matter how hard we try, we’ve never been able to collect, refine, transport, distribute and use gaseous fuels without leaking some portion of them. The more we look at our gas supply chain, the more leaks we find [5]. Because these fuels contain the potent greenhouse gas methane, small leaks have big climate consequences. Estimating conservatively, we find that the emissions from these leaks are just as large as those from actually burning the gas [6]. This means that, in the best case, renewable natural gas still has at least half the emissions of conventional fossil gas. But studies show that renewable natural gas facilities actually leak more than fossil natural gas facilities [7]. When this is factored in, the emissions from renewable natural gas are just as high as those from conventional natural gas.

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The second claim, that every ounce of renewable natural gas burned is an ounce of methane not emitted, is false because it assumes all the gas supplied by a hypothetical renewable natural gas system would otherwise be leaked (not burned). This simply isn’t true. First, as the constant flame at landfills across the country shows, many potential sources of renewable natural gas already burn it (this is called flaring). If this gas can be collected to make renewable natural gas, it can be flared without incurring the leaks and cost of the downstream infrastructure [8]. Second, the amount of theoretically capturable gas currently being released to the atmosphere is less than 1 percent of the fossil natural gas demand [9]. Proposing a renewable natural gas system of any meaningful size would mean intentionally generating this gas, rather than diverting gas already being released. Claiming credit for these supposed emissions reductions by first creating the emissions they are based on is disingenuous, to say the least.

Besides the fact that renewable natural gas isn’t actually clean, it also is and will remain an extremely limited resource. All the renewable natural gas produced in 2020 amounts to just 0.2 percent of U.S. natural gas consumption [10]. And if all technically feasible sources were developed (including building out massive new gas infrastructure to do so), renewable natural gas would only have the potential to meet 1.3 percent of current U.S. fossil gas consumption [11]. Despite its limitations as an available resource, proponents of renewable natural gas count it as a key component of any net-zero target, often assuming significantly more use than what is understood to be technically possible [12].

This short supply also makes renewable natural gas expensive. The price of renewable natural gas varies between two and fifteen times more expensive than fossil gas [13]. If the average U.S. home used this renewable natural gas, they would spend between $1,800 and $14,000 just to keep their homes warm during the winter [14]. By comparison, households heating with electric heat pumps would spend just $600 (which is already a savings compared to spending $930 to heat with fossil natural gas) [51]. In addition to this household spending, any commitment to renewable natural gas will involve continued investment in the gas distribution network, either stranding these assets or locking in emissions for the lifetime of this infrastructure.

Given the extremely limited supplies of renewable natural gas, and existing hard-to-decarbonize uses of fossil natural gas [16], we cannot afford to use renewable natural gas for building decarbonization. Further, because of its chemical similarity to fossil natural gas, renewable natural gas generates the same harmful pollutants [17] associated with damaging health impacts, most notably a significantly increased risk of asthma [18]. Even if your stove runs on renewable natural gas, it still releases toxins into your home.

In contrast, electrification is ready to be deployed today to decarbonize buildings and eliminate these sources of air pollution. It also delivers energy bill savings to households in the face of rising fossil fuel prices; expensive renewable natural gas only makes this case stronger. Any investment in new gas infrastructure (whether renewable or not) is a delay and distraction from building a truly clean electric future.

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Sam Calisch is the Head of Special Projects at Rewiring America, where he conducts research, writes, and occasionally dresses like a heat pump. He also is a founder of Channing Street Copper, a start-up broadening access to electrification by commercializing a retrofit-ready induction range. Previously, Sam was a Research Fellow at Lawrence Berkeley National Lab and has run projects with the National Science Foundation and Department of Energy. Sam completed his PhD at MIT and BA at Grinnell College.

Acknowledgement

The author would like to thank Steve Pantano, Leah Stokes, Ari Matusiak, Sarah Lazarovic, and Joel Rosenberg of Rewiring America for helping bring this piece together.

Notes:

[1] Renewable natural gas is also sometimes called sustainable natural gas, biogas, biomethane, marsh gas, sewer gas, compost gas, swamp gas and a host of other names. Sometimes these other names are used to refer to the raw feedstock gasses, while renewable natural gas is reserved for the gas after it has been “upgraded”, or refined to pipeline quality.

[2] For example, see this 2022 McKinsey report, this 2022 American Gas Foundation report, or this 2022 report from University of Utah. Utilities frequently release plans incorporating renewable natural gas, like this 2021 report from SoCalGas and this 2020 report from Washington Gas.

On a larger scale, a December 2022 House Oversight Committee report documents how methane management has been used as “social license” by Big Oil companies to continue investing in fossil fuel production. For example, an internal email from the American Petroleum Institute, states that the group’s climate policy specifically promoted the continued use of natural gas.

[3] Hydrogen and other “clean fuels” are often proposed alongside renewable natural gas in this proposition. In the context of building decarbonization, these other energy carriers also have a host of issues. For instance, a 2022 report assessing viability of hydrogen proposals found serious concerns about safety, cost and scale for distributing hydrogen for building decarbonization. A 2021 report found that just 7 percent of the gas energy delivered could be replaced with hydrogen, and that hydrogen leaked at three times the rate of fossil gas. Reporting in 2022 showed evidence that studies touting hydrogen have been funded and influenced by the gas industry. For simplicity, we only discuss RNG in this piece, and will address these other energy carriers in future work.

[4] All natural gas varies in chemical composition, but is chiefly composed of methane. The percentage of methane present in fossil gas at the wellhead can vary a great deal, and must be purified before entering a pipeline. According to Fundamentals of Natural Gas Processing, “pipeline quality gas” consists of a minimum of 75 percent methane, and a maximum of 10 percent ethane, 5 percent propane, 2 percent butanes, 0.5 percent pentanes and heavier hydrocarbons, 3 percent nitrogen and other inert gasses, 3 percent carbon dioxide. There are also limits on the maximum amount of hydrogen sulfide, total sulfur, oxygen and water vapor present. Renewable natural gas must be upgraded to these same pipeline quality standards from the raw biogas feedstock. After this refining, the methane content of the renewable natural gas is the same as fossil natural gas, but the trace gasses present may still vary, according to a 2021 EPA report.

[5] A 2021 study found that the majority of U.S. urban natural gas emissions were not accounted for in greenhouse gas inventories, finding an average leak rate between 3.3 and 4.7 percent from well to urban customer. A 2018 study found that methane emissions were 60 percent higher than previously estimated by the EPA, meaning approximately 2.3 percent of the U.S. gross fossil gas production is lost to leaks. A 2021 study showed that rates of production stage leaks alone contribute between 0.9 and 3.6 percent, adding approximately 40-160 percent to the equivalent emissions of combustion. Other studies have found even higher values, for example a 2011 study estimated the leak rate at 3.6 percent to 7.9 percent. A 2021 study looked at post-meter leaks in natural gas stoves, finding they leaked 0.8-1.3 percent of the gas they consumed. A 2020 study found water heaters leaked 0.39-0.93 percent of the gas they consumed.

It is worth noting that “certified” natural gas (also called “differentiated” natural gas, or “responsibly sourced” gas) refers to natural gas from a facility with a low rate of methane leakage, but these certifications (like the MiQ standard) only focus on leakage from production and do not address leaks in distribution or on-site use. This 2022 report from the Environmental Defense Fund presents detailed concerns about the mitigation potential of these certifications, including a lack of standards for measurement, the limited uptake, and the incentives for companies to “cherry-pick” within their energy portfolios.

[6] Taking a conservative estimate of 3% leakage rate, the 20 year global warming potential of methane of 81.2, the emissions factor of natural gas of 53 kg CO2e / MMBTU, a heat content of 1,037 BTU per cubic foot, a proportion of methane in natural gas of 97 percent, and a density of natural gas of 0.8 kilograms per cubic meter, we find that for every kilogram of carbon emissions released from combustion, approximately 0.98 kilograms of equivalent carbon emissions are released from methane leaks. This means that roughly half of total emissions from using natural gas come from methane leaks.

[7] In a 2019 survey of renewable natural gas plants, the average leakage rate was 4.6 percent, roughly double the gas industry average even before including transmission, distribution, and combustion. At this leakage rate, renewable natural gas retains over two-thirds the emissions of fossil gas. Wastewater treatment plants, a major source of renewable natural gas, were even higher at 7.5 percent on average, with some plants as high as 15 percent. A 2020 report found that for leakage rates above 6 percent, the equivalent emissions of intentionally produced RNG is actually higher than that of conventional fossil gas. That is, for leakage rates observed in existing facilities, emissions from RNG are just as high as fossil gas.

[8] Critically, the destruction removal efficiency of flaring must be greater than that of the downstream gas infrastructure plus eventual combustion. A 2014 study suggests flaring efficiency is above 98 percent, but a 2022 study shows that flaring in oil and gas fields can regularly be as low as 91 percent, emphasizing the need for careful control and monitoring.

[9] According to a 2020 article, the total amount of capturable methane sources currently being vented is less than 1 percent of the current fossil gas resource. Applying the climate benefits of these sources to a hypothetical RNG system capable of meeting any significant portion of current fossil gas demand is not realistic. To have an RNG system that can meet our demands, the feedstocks would very likely be intentionally produced. Because RNG from such intentionally produced methane streams does not mitigate an existing source of emissions, it has approximately equivalent emissions to fossil gas.

[10] Argonne National Lab tracks RNG facilities and maintains up-to-date counts of existing and planned facilities. As of 2020, there were approximately 60 trillion BTU per year of RNG produced. Of these, approximately 46 trillion BTUs came from landfills, 7 trillion from livestock, 4 trillion from food waste, and 3 trillion from wastewater treatment. This amounts to approximately 0.2 percent of U.S. natural gas consumption, according to the EIA’s Natural Gas Consumption by End Use.

[11] The USDA’s Biogas Opportunities Roadmap estimates there exist about 13,000 sites in the U.S. that could host a biogas system (about 2,000 of them are currently built out). Taken together, these potential sites could generate 650 billion cubic feet of gas per year (or about 350 trillion BTU per year). Critically, this biogas is made up chiefly of methane (40-60 percent) and carbon dioxide (30-50 percent). This means the usable (methane) portion of this biogas is roughly 360 billion cubic feet. In NREL’s Biogas Potential of the United States, the authors estimate the methane potential from landfill material, animal manure, wastewater, and industrial, institutional, and commercial organic waste at 420 billion cubic feet (430 trillion BTU per year).

While this may sound like a lot of gas, the U.S. consumption of fossil gas in 2020 was over 30 trillion cubic feet per year according to the EIA’s Natural Gas Consumption by End Use. This means if the infrastructure required to convert, harvest, collect, transport, and distribute the biogas from all potential sources in the U.S., the total technical potential of methane production by organic sources is just 1.3 percent of national consumption. Note that some studies have quoted higher percentage estimates, but this generally refers to the percentage of natural gas used for electricity generation (about 11 trillion cubic feet), rather than the full set of uses including residential, commercial, industrial, and transportation sectors.

Additionally, a California study found the state had the theoretical potential to produce approximately 90 billion cubic feet. In 2020, California consumed 2.1 trillion cubic feet of fossil gas, an upper bound of 4 percent of the supply that could potentially be met with RNG. A 2021 study for Philadelphia Gas Works found that “decarbonized gasses…are limited in terms of commercialization or total availability” and that “a full transition to decarbonized gasses in Philadelphia would likely require significant amounts of synthetic natural gas, a source of methane that is not yet commercialized.”

[12] For instance, a 2021 American Gas Association report assumes over 5 quadrillion BTUs of RNG will be used (excluding any used for electricity generation), over ten times higher than the NREL bound on maximum methane potential quoted above.

[13] A 2019 report by the American Gas Foundation itself found that RNG is likely to be available at costs of $7/MMBtu to $45/MMBtu. A 2016 report for the California Air Resources Board found that costs per MMBTU for RNG ranged from $30 to over $100 for dairies, $15 to $22 for municipal solid waste, $7 and over $50 for landfills, and between $9 and over $50 for wastewater treatment plants. According to the EIA, the city gate price of fossil gas is about $3.30/MMBTU. In short, the price of RNG varies between 2 and 15 times as expensive as fossil gas.

Under the most optimistic circumstances at very low production volumes, these data imply that RNG is over twice as expensive as fossil gas. As more RNG is produced, less optimal sources must be used, driving up the price and exacerbating the differential with fossil gas. For example, just 20 percent of the potential RNG resource is accessible at two times the price of fossil gas. In producing just half of the potential RNG resource, the price jumps to four times the price of fossil gas. By the time we are producing nearly the total technical potential, the price is over 15 times as expensive.

[14] This is based on estimates from the EIA’s Winter Fuels Outlook, which estimates natural gas bills during this winter will cost households $931 on average.

[15] For instance, see this 2022 article comparing the costs of winter heat between fossil fuels and electric heat pumps.

[16] These include the use of natural gas in industry as a feedstock to produce chemicals, rather than purely as an energy source.

[17] This 2020 EPA publication outlines the formations of the relevant pollutants (NOx, PM2.5, and benzene). The predominant mechanism of NOx formation is thermal, and happens simply because nitrogen and oxygen molecules are present in a high temperature zone. Benzene (C6H6) and PM2.5 (usually larger molecular weight hydrocarbons) are principally created through incomplete combustion, which is governed by the features of fire chamber and gas flow.

[18] A growing body of research establishes the link between residential gas appliances and harmful health effects, including childhood asthma, adult cancers, and dementia. A 2013 review article established a 42 percent increase in likelihood of asthma for children living in homes with gas stoves. A 2022 article estimated that 12.7% of current childhood asthma is attributable to gas stoves. A 2022 article documented gas stoves causing unsafe levels of benzenes, which have been linked to cancers. A 2019 review article and a 2021 article both established a link between the pollutants produced by gas stoves (PM2.5 and NOx) and an increased risk of dementia and cognitive decline.