RNG stands for renewable natural gas, a fuel produced by capturing methane from organic waste sources like landfills, dairy farms, and wastewater treatment plants. Once processed, it’s chemically almost identical to the fossil natural gas that flows through pipelines and powers homes, but its carbon footprint is dramatically lower because the methane would have escaped into the atmosphere anyway. In the U.S., RNG already accounts for roughly 84% of all natural gas used as transportation fuel.
Where RNG Comes From
RNG starts as biogas, a mix of methane and carbon dioxide that forms when bacteria break down organic material in oxygen-free environments. This process, called anaerobic decomposition, happens naturally in landfills, manure ponds, and sewage systems. The difference with RNG production is that the gas is captured instead of drifting into the air.
The most common sources are municipal solid waste landfills, which generate biogas continuously as buried trash decomposes. Dairy farms and livestock operations collect it from manure lagoons or specially built digesters. Wastewater treatment plants produce it as a byproduct of sewage processing. Food manufacturers, paper mills, and breweries also generate usable biogas from their waste streams. Raw biogas from these sources contains 45% to 65% methane, with the rest being mostly carbon dioxide and smaller amounts of hydrogen sulfide, moisture, and other impurities.
How Biogas Becomes Pipeline-Quality Fuel
Raw biogas can generate electricity and heat on-site, but it’s not clean enough to inject into a natural gas pipeline. Turning it into true RNG requires an upgrading process that strips away everything except methane. The first step removes moisture, hydrogen sulfide, and trace contaminants. Then the main upgrading step separates out carbon dioxide using one of four industrial-scale technologies: absorption (using a liquid solvent to dissolve CO2), adsorption (using solid materials that trap CO2 under pressure), membrane filtration (pushing gas through selective barriers), or cryogenic separation (cooling the gas until CO2 liquefies).
The goal is a methane purity of at least 95%, though gas injected into utility pipelines typically hits 96% to 98%. At that concentration, RNG is functionally interchangeable with conventional natural gas. It flows through the same pipelines, burns in the same furnaces, and fuels the same vehicles without any equipment modifications.
How RNG Reduces Emissions
The climate case for RNG is straightforward: methane is a potent greenhouse gas, roughly 80 times more effective at trapping heat than carbon dioxide over a 20-year window. When landfills, manure lagoons, and sewage plants release methane freely, it contributes significantly to warming. Capturing that methane and burning it as fuel converts it into the far less potent CO2, and it displaces fossil natural gas that would have been drilled, processed, and burned separately.
On a full lifecycle basis, RNG can reduce greenhouse gas emissions by about 95% compared to diesel. In some cases, particularly dairy farms with open manure lagoons that currently vent large volumes of methane, RNG production actually achieves a negative carbon intensity score. That means the emissions avoided by capturing the methane outweigh the emissions created by processing and burning the fuel. Not all RNG sources perform equally, though. Landfill gas projects, while beneficial, typically have higher carbon intensity scores than dairy manure projects because landfills already capture some methane through flaring.
What RNG Powers
Transportation is RNG’s biggest market today. In 2022, RNG qualified as a cellulosic biofuel under the federal Renewable Fuel Standard, with production reaching 55 billion cubic feet. That covered 84% of all natural gas consumed as vehicle fuel in the United States, primarily in heavy-duty trucks, transit buses, and refuse collection vehicles that run on compressed or liquefied natural gas.
Beyond vehicles, RNG serves the same roles as conventional natural gas. Utilities can blend it into their distribution networks to lower the carbon intensity of residential heating and cooking. Power plants use it to generate electricity. Industrial facilities burn it for process heat. One study from the National Association of Clean Water Agencies estimated that energy generated at U.S. wastewater treatment plants alone could potentially meet 12% of national electricity demand, though most of that potential remains untapped. Most landfill biogas projects today still use the gas for on-site electricity generation rather than upgrading it to pipeline-quality RNG.
How Fast the Industry Is Growing
The RNG sector has expanded rapidly. North America now has over 500 operational RNG facilities, up from just 31 when the RNG Coalition was founded in 2011. Another 153 facilities are under construction, and 293 more are in planning and permitting stages, putting the industry on track toward a target of 1,000 operational facilities by the end of 2030.
Several policy drivers fuel this growth. The federal Renewable Fuel Standard creates demand by requiring transportation fuel suppliers to blend in biofuels, and RNG qualifies as a cellulosic biofuel with high credit values. California’s Low Carbon Fuel Standard assigns carbon intensity scores to different fuel pathways, and RNG from dairy manure scores so favorably that it commands premium pricing. These incentive structures have made RNG production increasingly attractive to landfill operators, wastewater utilities, and agricultural operations looking to turn a waste management cost into a revenue stream.
RNG vs. Conventional Natural Gas
Once RNG enters a pipeline, there’s no physical way to distinguish it from fossil natural gas. Both are predominantly methane. The difference is entirely in origin and lifecycle emissions. Fossil natural gas is extracted from underground geological formations, processed, and transported, with methane leaks possible at every stage. RNG captures methane that already exists at the surface as a byproduct of biological processes.
RNG is not a limitless resource. Its supply is constrained by the amount of organic waste available, and it could never fully replace the volume of fossil natural gas consumed in the U.S., which totals roughly 30 trillion cubic feet per year. Current RNG production of around 55 billion cubic feet is a small fraction of that. Its value lies not in replacing all fossil gas but in capturing waste methane that would otherwise warm the atmosphere, while producing usable energy in the process.