Grantee Research Project Results
Final Report: Development of a Standardization Method for Isotopic Tracing of Fugitive Sources of Methane in Atmospheric Gas Mixtures using 14C, 13C, and 2H
EPA Contract Number: 68HERC23C0018Title: Development of a Standardization Method for Isotopic Tracing of Fugitive Sources of Methane in Atmospheric Gas Mixtures using 14C, 13C, and 2H
Investigators: Ahearn, Sean
Small Business: Beta Analytic
EPA Contact: Richards, April
Phase: I
Project Period: December 1, 2022 through May 31, 2023
Project Amount: $100,000
RFA: Small Business Innovation Research (SBIR) Phase I (2023) RFA Text | Recipients Lists
Research Category: SBIR - Water , SBIR - Homeland Security , SBIR - Sustainability , SBIR - Air and Climate
Description:
Methane (CH4) gas from natural (wetlands and groundwater) versus anthropogenic (oil and gas, agricultural, and landfills) sources are difficult to source track and attribute to any single root cause responsible for increased global methane emissions. Currently, methane emissions are assessed from a top-down or bottom-up approach using concentration-based measurements. While detecting the presence of methane emissions is an important first step, differentiating between methane molecules to understand their source is a complex, pivotal next step towards reducing greenhouse gas emissions. Isotopic testing of CH4 has the potential to differentiate modern versus "fossil" carbon using radiocarbon (14C) and stable isotopes of carbon-13 (13C) and hydrogen-2 (2H) for source tracking. Currently, these isotopic testing standards are widely used for 14CO2 emissions testing in a variety of contexts such as ISO standardizations, and they are often reported under the ASTM D6866 protocol. The objective of the project focused on developing 3rd party testing protocols for gas conversion of methane, and other associated gases (CO2 and CO) and hydrocarbons composed of C1-C5 gases, for isotopic analysis using Method B of ASTM D6866. This work addresses global demand for a reliable analytical testing method to authenticate renewable feedstocks, landfill emissions, and other hydrocarbon gases co-processed, produced, or emitted by the energy sector; these methods are critical for testing natural gas in the emerging hydrogen fuel economy. This work focused on standardization, analytical methodology development, gas separation, and catalytic conversion chemistry with quality assurance met through repeated measurements for accuracy, precision, and error determination to meet client needs. The radiocarbon results are reported as ratios of isotopic values of 14C/12C and/or 13C/12C and determined to a traceable standard NIST SRM 4990C (oxalic acid) modern carbon reference standard. ASTM D6866 Method B provides the most reliable and reproducible result through the detection of carbon isotopes using high-resolution accelerator mass spectrometry (AMS) and Isotope Ratio Mass Spectrometry (IRMS). Finally, methane gas and carbon dioxide gas isolation, catalytic conversion, and isotopic analysis were performed as a case study on South Florida landfills emissions testing.
Summary/Accomplishments (Outputs/Outcomes):
During the EPA SBIR Phase I funding period, the Beta Analytic Research and Development department (R&D) developed a robust pretreatment method for the conversion of hydrocarbon gases that was integrated into existing laboratory production services of precise isotopic testing methods with detection using widely accepted AMS and IRMS instruments. The scientific data showed success in high-yielding gas conversion efficiencies and gas chromatographic separations that were optimized to eliminate carbon memory. The quality assurance was determined through statistical analysis of replicate data sets and analysis of variance (ANOVA) determination of methane and carbon dioxide gas standards and mixed hydrocarbon gas standards. After verifying the reliability of the pretreatment methods on these gas standards, we differentiated emission sources, specifically landfill (modern or bomb carbon) emissions vs fossil fuel (fossil carbon) emissions of 14CH4 isolated and 14CO2 isolated gases that show different microbial pathways; these measurements are projected to improve methane point and non-point source tracking and the ability to confirm bottom-up and top-down accounting of methane, specifically as emissions regulations evolve.
Conclusions:
To meet global demand for testing under ASTM D6866, efforts were also undertaken to report isotopic results within a reasonable turn-around-time (TAT); these were critical new findings revealed through customer discovery and value proposition identification that are guiding our commercialization plan. Furthermore, the development of gas conversion and separation methods that can be scaled-up to meet global demand is a critical next step in this project. Our customer discoveries of renewable natural gas (RNG) producers suggest that testing of RNG feedstocks for their biobased content via ASTM D6866 is expected to confirm renewable content in co-processed mixtures. Finally, our customer discoveries have confirmed that radiocarbon will also play a role in the hydrogen fuel economy as a renewable source verification method.
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.