Together these facilities have produced over 59 million MMBtu or the equivalent of approx 460 million gallons of diesel fuel—enough for fuel 50,000 waste trucks, Argonne data show. These numbers are probably already higher given that approx 200 more projects were under construction or in planning mode when Argonne last updated its database in January 2022.
But that’s still less than 0.2 percent of total U.S. fossil gas production last year.
Most of them RNG projects traditionally involve landfills, which typically yield the largest amount of fuel for the lowest cost. At these sites, a maze of equipment collects gases from decomposing organic materials and pipes them to a central processing point.
In recent years, however, companies have begun to invest heavily in agricultural projects. Dairy farms, in particular, are a major source of methane, due to their open manure lagoons (not to mention all the gas the cows release when they burp). More farms are now capturing and recovering methane by adding flexible covers and pipes to their lagoons or by storing the manure in closed tanks for anaerobic digestion.
in California, RNG of lactic methane can be considered “carbon-negative” under the state’s low-carbon fuel standard, which provides incentives for producers of alternative fuels. Because the state doesn’t regulate methane emissions from the dairy industry the way landfills do, any facility that keeps dairy methane out of the atmosphere is considered an emissions remover. While environmentalists criticized this approach as wishful accounting, the scheme unleashed a “brown gold rush’ by energy giants including Shell, BP and Chevron.
A separate policy is required in California RNG production from food scraps. The law, which took effect last year, requires municipalities to separate organic waste from garbage so that the state’s banana peels and chicken bones can be turned into compost or RNG, not garbage. Nationwide, only approx 1.5 percentage of excess food is sent to anaerobic digesters, in part because of the cost and complexity involved in collecting waste from homes and businesses.
It does RNG fit into a cleaner future?
Despite its limitations, some experts believe RNG may yet play a close role in the country’s clean energy future.
About three quarters of the current one RNG delivery is currently used in transportation, including heavy trucks. In the coming decades, however, transportation’s share will decline as utilities inject more of the fuel into pipelines to heat buildings and power gas appliances. Earthjustice’s Saadat said more ideal uses for the fuel could include high-heat industrial applications that are more difficult to electrify than homes or trucks and for which few clean energy solutions are available today.
“It would certainly be better, though not ideal, if you focus that little RNG a resource to displace fossil methane that we use in cement or glass production, not in road transport,” he said.
The commercial and industrial sectors account for less than 1 the percentage of those existing in the country RNG customer base, although it is expected to catch up almost 10 percentage of demand growth in 2040, according to a report by the Renewable Thermal Collaborative. But even everyone RNG supply went only to the production of steel, chemicals or other applications, it still would not be enough to power all of today’s most energy-intensive processes.
“If we decide we want to RNG our way to fully decarbonize, we really can’t because there just isn’t enough feedstock,” Collison said. “And that’s good. RNG will be part of the basket of solutions.”
Other organizations are watching RNG as a temporary solution while they work to electrify the most complex parts of their construction operations.
For the University of California (UC) system that supports some 6,000 buildings across 10 campuses, which primarily means dealing with combined heat and power plants. In the last decade, UC is working to reduce its emissions through energy efficiency improvements and adoption of renewable energy. As a result, almost 80 percent of its remaining emissions come from burning fossil gas in on-site power generators.
Gas plants provide power, hot water and steam to hospitals, research centers and other buildings and are “an important resilience tool to protect patient lives and billions of dollars of research in the face of increasingly frequent power outages caused by wildfires and grid stress,” said Sam Shabaker, UCrenewable energy manager.
Replacement of combined heat and power plants and associated pipes, loops and ducts is a “a billion dollar challenge that UC the system will handle the next phase of its decarbonization journey,” he added in an email.
Meanwhile, UC aims to displace 40 percentage of your annual gas consumption with RNG from 2030. The university system has invested $21 million to build a facility in Shreveport, Louisiana, that produces fuel from a municipal landfill. UC also secured long-term purchase agreements RNG from an anaerobic bioreactor that converts agricultural waste in Wisconsin. While neither project will directly supply California campuses, the university can count RNG production as their own, in the same way that enterprises can claim “renewable energy credits’ for wind and solar energy produced elsewhere.
In particular, Shabaker said, UC is supply only RNG which has previously been ventilated or ignited, i.e “diffuse methane’ for beneficial use.
His statement reflects another tension that underlies the wider debate over so-called renewable gases. One of the main concerns is that, generally speaking, companies may choose not to reduce methane pollution by using other means—such as further limiting food waste, reducing household garbage, or improving dairy operations—because doing so would reduce their revenue stream.
“There is a lot of risk in creating markets to incentivize this kind of methane capture,” Saadat said. “Because when you commoditize pollution, you may actually be perversely incentivizing it.”