Renewable Natural Gas
The Science of "Renewable" Natural Gas
"RNG is made by processing biogas, making a fuel that is composed mostly of methane and that can be mixed with fossil natural gas in gas pipeline systems. Biogas is a mixture of methane and carbon dioxide as well as other impurities that is produced from anaerobic digesters (including some wastewater treatment plans as well as farm-based systems using manure) and can be captured from landfills. The biogas can itself be used as a fuel, for instance to 2 generate electricity or heating, but biogas is not suitable for use in pipeline distribution systems. In the final Scoping Plan for the New York Climate Action Council, we specified that whenever possible, biogas should be used directly at the site of production, and preferably used in fuel cells rather burned to generate electricity. Our plan further stated that the use of biogas as biogas was to be preferred to processing it into RNG. There are two reasons for this: 1) it takes energy to process biogas into RNG, and so this is inherently inefficient and increases greenhouse gas emissions; and 2) the latest peerreviewed science shows that methane emissions from processing biogas into RNG can be substantial, as shown in a review paper published last year (see: Bakkaloglu, Cooper, and Hawkes. 2022. Methane emissions along biomethane and biogas supply chains are underestimated. One Earth 5: 724-736, doi:10.1016/j.oneear.2022.05.012). Converting biogas into renewable natural gas is wasteful and further contributes to greenhouse gas emissions, with no benefit other than to allow the gas to be pumped into the traditional fossil gas distribution systems."
Professor Howarth's full testimony can be found here: Sen. Natural Resources & Energy 02-08-2023 10:15AM - YouTube. This link will take you to his full written testimony: November 11, 2004 (vermont.gov) .