• Fair Oaks Farm’s digester generates enough R-CNG to displace some 1.5 million gallons of diesel, and to cut annual GHG emissions by 19,500 tons CO₂e. That’s a 43% reduction in carbon emissions per gallon of milk, a selling point that helped the company negotiate an exclusive supply agreement with the national grocery chain Kroger.

• The Sacramento BioDigester was built by a public-private partnership in 2013. Atlas Disposal and other haulers collect the organic wastes from area businesses and deliver it to the digester, which produces enough R-CNG to displace 500,000 gallons of diesel a year and divert up to 40,000 tons of organic waste from landfills. Atlas’s subsidiary ReFuel Energy Partners uses that R-CNG to power its 30 natural gas powered refuse trucks. Atlas is committed to converting its entire refuse fleet to natural gas as older diesel vehicles retire.

Nationwide, renewable natural gas has grown more than 70% annually in recent years, facilitated by inclusion in the EPA’s Renewable Fuel Standard (RFS2), which sets a minimum volume for the amount of renewable fuel that must be used in the transportation sector. Renewable natural gas production for transportation totaled 151 million gasoline gallon equivalents in 2017, up from 125M GGEs in 2016 and 90M GGEs in 2015.

R-CNG derived from organic waste is chemically similar to geologic compressed natural gas (CNG), and can be used in the same applications—heating or cooling buildings, generating electricity, or fueling vehicles. But unlike fossil CNG, it’s a fully renewable fuel.

According to Argonne National Lab’s GREET model, R-CNG produced from anaerobic digestion of food waste is net-carbon negative over its lifecycle, including production, use and avoided emissions—i.e., making and using it results in lower atmospheric GHG than if the fuel were never made or used. R-CNG derived from a food waste digester meets or exceeds international goals of reducing GHG emissions 80% from 2005 levels by 2050.

Lifecycle carbon intensity of various fuels (grams/CO2e/MJ) based on GREET 2016 model. (MSW, municipal solid waste; WWTP, wastewater treatment plant.) Source: “Cow Power” case study. Click to enlarge.

R-CNG can achieve the greatest GHG reductions of any transportation fuel today—70% or more as compared to gasoline or diesel.

—Marianne Mintz of Argonne National Laboratory’s Energy System Division, co-author

R-CNG also saves on fuel costs and allows truck and bus fleets to operate more quietly and efficiently, generating fewer pollutants that threaten public health. Compared to diesel, it reduces carbon monoxide up to 70%, nitrous oxide up to 87%, and particulate matter up to 90%, as well as reducing noise up to 90%.