Greenhouse Gas Measurment Methods
Greenhouse gases are carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), sulfur hexafluoride (SF6), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and other fluorinated gases (e.g., nitrogen trifluoride (NF3) and hydrofluorinated ethers (HFEs) all of which contribute to global warming. The U.S. Environmental Protection Agency (EPA) now requires the reporting of annual greenhouse gas emissions by major sources, specifically including upstream (fossil fuel suppliers) and downstream (fossil fuel users) sources.
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Greenhouse Gas Monitoring
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New greenhouse gas reporting requirements necessitate the installation of Continuous Emissions Monitoring Systems (CEMS) which are gas/air flow meters and other monitoring equipment, training of staff and development of internal electronic data management and record keeping systems.
The overall purpose is to collect greenhouse gas emission data by facility process, aggregate the data and then calculate overall greenhouse gas emission by major source which will then be reported to the EPA as metric tons of CO2 emissions (CO2e) per year. CO2e values can be converted and compared to types of greenhouse gas emissions that may vary by source type.
Calculating CO2 Emissions
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When calculating CO2 emissions from fuel combustion, a four-tier methodology is implemented based on annual fuel consumption data from records or flow meters, high-heat values, CO2 emission factors, periodic measurements of carbon content, hours of operation, and/or CEMS data. For solid, liquid, and gaseous energy sources (i.e., inputs) for processes, use continuous flow meter measurements or monthly aggregates of solid inputs and the carbon content of inputs.
QA/QC and Record Keeping
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Quality assurance and quality control (QA/QC) of all data, accurate record keeping and regular maintenance of CEMS equipment is required. EPA will require submission of all of these records along with the methodology and associated calculations used when reporting CO2e.
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