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Improving Characterization of Anthropogenic Methane Emissions in the United States (2018)

Chapter: Appendix F: Common Units for Reporting Methane Concentrations and Emissions

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Suggested Citation:"Appendix F: Common Units for Reporting Methane Concentrations and Emissions." National Academies of Sciences, Engineering, and Medicine. 2018. Improving Characterization of Anthropogenic Methane Emissions in the United States. Washington, DC: The National Academies Press. doi: 10.17226/24987.
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APPENDIX F

Common Units for Reporting Methane Concentrations and Emissions

Methane concentrations, emissions, and flow rates (metered sources) are commonly reported using a wide range of units. This appendix focuses primarily on units used in this report.

METHANE CONCENTRATIONS

Volumetric mixing ratio (v/v or l3/l3): Parts per million (ppm), parts per billion (ppb), and parts per trillion (ppt); 1 ppm = 1,000 ppb; 1 ppm = 1,000,000 ppt.

Mass per unit volume (m/v or m/l3) at standardized temperature and pressure: milligrams or grams per cubic meter (mg m–3, g m–3) at standardized temperature and pressure conditions (commonly 0°C and 101.325 kilopascals)

Note: Conversions from volumetric to mass-based units require use of the ideal gas law equation: PV = NRT, where

P = pressure in atm,

T = temperature in Kelvin [=deg C + 273],

R = molar gas constant, where R = 0.082058 L atm mol–1 K–1

1 mole methane = 16.04 g.

METHANE EMISSIONS

Mass per time (m/t): megagrams, or terragrams per year (Mg yr–1, Tg yr–1)

Mass per unit area per time (m/(l2 t): grams per square meter per day (g m–2 d–1). Used for area sources (i.e., manured soils; landfills).

Suggested Citation:"Appendix F: Common Units for Reporting Methane Concentrations and Emissions." National Academies of Sciences, Engineering, and Medicine. 2018. Improving Characterization of Anthropogenic Methane Emissions in the United States. Washington, DC: The National Academies Press. doi: 10.17226/24987.
×

Mass CO2 equivalents per time: Requires multiplication of mass methane by global warming potential (GWP) for methane. GWP varies through time (=28 per IPCC 5th Assessment Report).

METHANE FLOW RATES (METERED SYSTEMS)

Standard cubic feet per minute: Cubic feet per minute at 60°F and 14.7 pounds per square inch (psi) pressure.

Standard cubic meters per minute: Cubic meters per minute at 15°C and 100 kilo-pascal pressure.

Normal cubic meters per minute: Cubic meters per minute at 0°C and 101.325 kilo-pascal pressure.

Multiplication factors for common metric units

1,000,000,000,000 1012 tera
1,000,000,000 109 giga
1,000,000 106 mega
1,000 103 kilo
Suggested Citation:"Appendix F: Common Units for Reporting Methane Concentrations and Emissions." National Academies of Sciences, Engineering, and Medicine. 2018. Improving Characterization of Anthropogenic Methane Emissions in the United States. Washington, DC: The National Academies Press. doi: 10.17226/24987.
×
Page 225
Suggested Citation:"Appendix F: Common Units for Reporting Methane Concentrations and Emissions." National Academies of Sciences, Engineering, and Medicine. 2018. Improving Characterization of Anthropogenic Methane Emissions in the United States. Washington, DC: The National Academies Press. doi: 10.17226/24987.
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Page 226
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Understanding, quantifying, and tracking atmospheric methane and emissions is essential for addressing concerns and informing decisions that affect the climate, economy, and human health and safety. Atmospheric methane is a potent greenhouse gas (GHG) that contributes to global warming. While carbon dioxide is by far the dominant cause of the rise in global average temperatures, methane also plays a significant role because it absorbs more energy per unit mass than carbon dioxide does, giving it a disproportionately large effect on global radiative forcing. In addition to contributing to climate change, methane also affects human health as a precursor to ozone pollution in the lower atmosphere.

Improving Characterization of Anthropogenic Methane Emissions in the United States summarizes the current state of understanding of methane emissions sources and the measurement approaches and evaluates opportunities for methodological and inventory development improvements. This report will inform future research agendas of various U.S. agencies, including NOAA, the EPA, the DOE, NASA, the U.S. Department of Agriculture (USDA), and the National Science Foundation (NSF).

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