“Renewable natural gas” (also known as RNG, methane gas, or biogas) is used as a strategy by gas utilities to avoid closure due to the state and local carbon neutrality goals. While landfill RNG collection projects are becoming more common across the United States, RNG is, at best, a temporary solution to achieving emission reductions, and at worst results in environmental harms that could offset the benefits of reduced fossil fuel use. The focus for emission reduction plans should be placed squarely on electrification paired with renewable electric generation.
RNG is a gaseous byproduct of decomposing organic matter and can be used to fuel vehicles or generate electricity and heat. For years RNG, primarily from landfills, livestock operations and wastewater treatment, has been used to produce small amounts of electricity. More recently, large-scale landfill RNG projects used to supplement conventional gas have become more prevalent.
Although RNG extracted from landfills has the potential to lower greenhouse gas emissions, landfill RNG potential isn’t sufficient to produce enough biofuels to substitute for fossil fuels. The technical potential for U.S. landfill gas is 1 Bcf per day (two-thirds of the total RNG potential in the United States), which is insignificant compared to the current U.S. gas consumption of 82.9 Bcf per day. Landfill RNG would need to be supplemented with RNG extracted from dedicated farmland. A paper published by Yale Economics concluded that the large-scale and destructive agricultural expansion needed to produce farmland RNG could negate its environmental benefits by endangering the forests it replaces. Farmland RNG production also requires a large amount of freshwater use, and a study published in Ecological Economics found that farmland RNG expansion would require freshwater needed for food production. These negative environmental impacts have the potential to offset the benefits of landfill and livestock RNG (preventing manure runoff into water supplies, reducing methane emissions). Despite these drawbacks, RNG is promoted by gas utilities as a viable alternative to electrification because of its purported ability to reduce emissions while keeping gas utilities’ business model alive.
The electric grid must transition to zero-emission sources like wind, solar, and hydro to reach 2050 emission targets without the negative land-use impacts that come with farmland RNG production expansion. A study from UC Davis found the total RNG potential in California could only provide 4.1 percent of the state’s conventional gas demand, meaning RNG cannot replace gas without importing substantial materials from out of state. A report from the Union of Concerned Scientists came to a similar conclusion for both California and the United States with regard to RNG transportation fuel..
Renewables like wind and solar are among the cheapest energy sources, making them the focal point of renewable energy infrastructure planning. There is little potential for RNG to reduce emissions at the same cost and scale as electrification resources.
