Recycling and repurposing waste has a long and storied history. Allison Emmerson, an academic working on the Pompeii I.14 excavation project, told The Guardian in April 2020, “We found that part of [the city of Pompeii, destroyed in 79 A.D.] was built out of trash. The piles outside the walls weren’t material that’s been dumped to get rid of it. They’re outside the walls being collected and sorted to be resold inside the walls.”
Today, recycling is critical to limiting global warming to no more than 1.5 degrees Celsius higher than pre-industrial levels. According to the Intergovernmental Panel on Climate Change, staying under that threshold should be enough to stave off most climate crises.
In 2023, using waste to produce fuel with characteristics similar to fossil fuels but with near-zero emissions is in the spotlight. Renewable natural gas (RNG) is one of the most promising. An August podcast by S&P Global said, “Renewable natural gas is headed for the moon. [It] has gained attention in recent years as a lower-carbon replacement for conventional fossil fuels.”
RNG could prove a lifeline for the oil and gas, and farming sectors. However, as with most new fuel technologies, there is debate over its eco-credentials. “While some tout ‘renewable natural gas’ as a way to mitigate climate change, others see a false solution,” wrote John Carey, a senior solar consultant at Energy Saving Pros, in his July blog on PNAS, a peer-reviewed journal of the National Academy of Sciences,
Recycling natural gas
RNG is made by collecting methane gas released from decaying organic waste found in municipal solid waste landfills, water recovery facilities, livestock and food production facilities and waste management operations. The gas can be pumped directly from the landfills or generated by putting the waste in “digesters.”
After several treatment stages to remove moisture, contaminants and other elements, the captured gas is converted to RNG and ready for transport via the existing natural gas pipe network to its final destination or liquefaction plants.
According to Clean Energy Fuels, a U.S. company that produces RNG, “It reduces carbon on two fronts.” The first is at the source by capturing methane. According to the U.N. Environmental Program, “Over a 20-year period, [methane] is 80 times more potent at warming than carbon dioxide.”
On the other front, RNG is usually 96% to 98% methane, meaning burning it in internal combustion engines produces little to no carbon dioxide. The U.S. Environmental Protection Agency (EPA) says RNG is a “biogas [which has a methane content between 45% and 65%] that has been upgraded for use in place of fossil natural gas,” In Europe, RNG also is known as biomethane.
The EPA says RNG can use the same infrastructure as fossil natural gas and has the same uses: “thermal applications, to generate electricity, for vehicle fuel or as a bio-product feedstock.”
Clean Energy Fuels noted that it can power heavy-duty trucks and buses, “replacing dirty diesel or gasoline” with little to no modification.
New lifelines
Oil and gas companies see RNG as a potential long-term source of revenue. “Phasing out fossil gas would leave oil and gas companies with massive stranded assets,” Tristan Brown, director of the Bioeconomy Development Institute, told PNAS in July. “So [RNG] is very appealing [as] they can reuse existing infrastructure.”
In October 2020, Chevron partnered with Brightmark Fund Holdings to create Brightmark RNG Holdings. As of May, they have 20 RNG-production projects in the U.S. In December, British Petroleum (BP) spent $3.3 billion to buy U.S.-based Archea Energy, an RNG producer. Shell Petroleum NV followed suit, buying 100% of Natural Energy Biogas A/S in February for $2 billion.
Farmers should receive significant revenue from RNG’s increasing popularity. For one, they produce a substantial portion of methane emissions. According to the EPA, “37% of methane emissions from human activity are the direct result … of livestock and agriculture practices.”
Secondly, the price of RNG is “eight to 20 times higher than the price of fossil natural gas,” given its ultra-low emissions. Dairy biomethane is classified as “negative emissions.” Robert Howarth, professor of ecology and evolutionary biology at Cornell University in the United States, told PNAS. “Dairy farms say they can make more money peddling RNG credits … than they do making milk.”
Expensive fuel
Dentons, a business consultancy, noted that RNG faces multiple challenges. First, it “is expensive … compared to other gas sources, [making it] not yet commercially viable … without incentives and grant programs.”
That higher price is partly down to feedstock availability. “Each RNG facility will need to procure enough long-term feedstock supply to ensure continuous operations,” Dentons’ paper said. “That can be difficult due to the cyclical nature of certain types of agricultural waste, as well as supply and demand issues created by more RNG facilities vying for the same resources.”
Another challenge is finding locations for RNG facilities close to landfills with the necessary infrastructure to transport the produced biomethane. “If a suitable location is not found, project proponents will need to build out infrastructure access in addition to the technical infrastructure required for their facilities,” Dentons explained.
The other issue is the “incredibly high” cost of producing RNG, as the technology used to capture methane from waste is still expensive. Converting RNG from gas to liquid is also “significantly” more costly than liquefying fossil natural gas, Dentons said. The Institute of Transportation Studies at the University of California, Davis, estimates converting RNG to liquid is at least 50% more expensive than fossil natural gas.
However, the Dentons paper stressed, “As RNG conversion and upgrading technology advances, and energy networks expand, we may see the … cost of RNG decrease with time.” That would be a similar dynamic to other non-fossil-fuels, the consultancy added.
Bright future?
Despite RNG being significantly more expensive than fossil natural gas, Europe and North America see its potential.
In September, the European Biogas Association (EBA) and Coalition of Renewable Natural Gas met with Pankaj Bhatia, global director of the Greenhouse Gas Protocol, a global framework to help companies measure their greenhouse emissions and get certified if they are below the protocol’s thresholds. Their meeting discussed certification options for RNG producers.
Currently, the protocol “doesn’t have accounting rules for biomethane certificates,” noted the EBA in the meeting’s press release. Having a recognized proof of eco-credentials and sustainability will be the “foundation for growing [the] biomethane market.” Bhatia told the media, “We agreed on plans for a workshop in 2024” as a first step toward certifying RNG in European and North American markets.
Ultimately, ensuring the success of RNG and similar low-emission fuels touting nearly identical characteristics to fossil fuels goes beyond economics. Stephen Edel, senior coordinator of NY Renews, an environment-focused advocacy group, told PNAS: “The debate is: Do we want to invest in maintaining the polluting gas system we have now, or do we want to fundamentally move off of combustion sources?”
