Methane (CH4) gas concentrations and dynamics emanating from natural (e.g., wetlands and groundwater) versus anthropogenic (e.g., oil and natural gas, agriculture and landfills) are of concern because of the regional and global need for estimations of atmospheric CH4 emissions and source tracking.1 Radiocarbon analysis can be used in an effort to understand methane point and non-point source emissions, incentivize the use of renewable natural gas (RNG) to produce net zero carbon pathways, and quantify and mitigate methane emissions from various “fossil” and “modern” carbon sources.2-4 The co-processing of fossil fuel methane from biogas has also created synergistic opportunities in blue hydrogen technologies that incorporate strategies to decarbonize natural gas and use hydrogen gas as a clean fuel using current refinery infrastructure. Other strategies identify carbon intensity (CI) in co-processed gases of propane and butane chemical intermediates generated in refinery production.
The U.S. Environmental Protection Agency (EPA) Renewable Fuels Standards Rule for 2023, 2024 and 2025 includes testing requirements for biogas and renewable natural gas (RNG) seeking to generate renewable identification numbers (RINs) under the program. The program requires that any fuels produced from biogas and RNG must submit ASTM D6866 test results to generate RINs.
All three-year engineering reviews of facilities upgrading biogas to RNG will be required to provide certificates of analysis (COAs) from an independent laboratory for their biogas at the digester or landfill, their RNG prior to the addition of any non-renewable components, and their RNG after it is blended with non-renewable components. Out of consideration for a timely registration process, RNG producers will be required to submit these COAs at their engineering reviews, rather than upon registration.
The rule also specifically requires ASTM D6866 as one of the standards that “must be used when measuring biogas properties,” and includes stringent recordkeeping requirements for biogas and RNG biogenic content measurements, which must be reviewed by third-party auditors under the RFS Quality Assurance Plan. The section of the Set rule focused on new biogas and RNG testing concludes, “that this requirement is necessary to ensure that RINs are only generated from renewable biomass.”
The Canadian Ministry of Environment and Climate Change published a Quantification Method (QM) for co-processing in refineries under the Clean Fuel Regulations. The QM requires ASTM D6866 testing to measure the biogenic content of the co-processed feedstocks used and the low-CI fuels produced in registered projects.
In order to obtain credits for the production of low CI fuels under a co-processing CO₂ Emissions Reduction project, they are required to measure the biogenic content of samples from each fuel, product, and hydrocarbon co-product via ASTM D6866 testing.
In June 2023, the European Commission adopted a revised methodology for calculating the biogenic content of biofuels and biogas under the Renewable Energy Directive (RED). Biogas producers whose products are co-processed have the choice to demonstrate compliance by either directly testing biogenic content via the carbon-14 method or through mass balance calculations based on the feedstocks used.
1. Lan, X.; Tans, P.; Sweeney, C.; Andrews, A.; Dlugokencky, E.; Schwietzke, S.; Kofler, J.; McKain, K.; Thoning, K.; Crotwell, M.; Montzka, S.; Miller, B.; and Biraud, S.; “Long-Term Measurements Show Little Evidence for Large Increases in Total U.S. Methane Emissions Over the Past Decade,” Geophysical Research Letter, 2019, 46, 4991-4999.
2. Kerfoot, H. B.; Hagedorn, B.; and Verwiel, M., “Evaluation of the age of landfill gas methane in landfill gas-natural gas mixtures using co-occurring constituents,” Environ. Sci. Processes Impacts, 2013, 15, 1153-1161.
3. Epsic, C.; Liechti, M.; Battaglia, M.; Paul, D.; Rockmann, T.; and Szidat, S., “Compound-Specific Radiocarbon Analysis of Atmospheric Methane: A New Preconcentration and Purification Setup,” Radiocarbon, 2019, 61(5), 1461-1476. doi:10.1017/RDC.2019.76.
4. Joung, D.; Leonte, M.; and Kessler, J.D., “Methane Sources in the Waters of Lake Michigan and Lake Superior as Revealed by Natural Radiocarbon Measurements,” Geophysical Research Letters, 2019, 46, 5436-5444.
Page last updated: September 2023