A.  Greenhouse gases (GHGs)

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Biogas, chiefly methane (CH4) and carbon dioxide (CO2), results from the natural decomposition of organic matter under anaerobic (no oxygen present) conditions. As a result, biogas is a promising renewable energy resource derived from waste biodegradation, but also a significant source of potent greenhouse gases (GHG) (methane is about 25 times more potent than the reference GHG, CO2, in terms of heating the Earth’s atmosphere). Typical biogas components are: volatile organic compounds (hydrocarbons), ammonia and hydrogen sulfide, and the majority gases methane  (35-70%) and carbon dioxide (15-40%). The relative gas proportions depend on the type of organic matter source material and biodegradation conditions [SGC, 2012].

 

B. Renewable Energy Resource

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Methane is a promising renewable energy resource derived from biomass (waste) decomposition by microbes. Microbes in soil, landfills, wastewater, wetlands, and the gut of ruminant livestock (like cows), naturally produce biogas methane, an extremely flammable gas that burns relatively cleanly as a fuel source. Capturing this valuable renewable resource depends on understanding methane production processes, quantifying biogas source magnitudes, and controlling fugitive emissions (from soil, wetlands, etc. as well as natural gas pipelines). Field measurements of CH4 emissions from these diverse sources are necessary in order to develop control systems and strategies to lower emissions and provide a net positive benefit to global climate.

 

Currently, most agricultural and municipal waste (landfills) emit uncontrolled quantities of biogas into the atmosphere, representing an untapped source of both renewable energy and GHG mitigation. Countries are working to reduce landfill disposal of organic material and to develop biogas from these waste streams for heat, electricity and vehicle fuel [SGC, 2012; Quebec, 2017]. Raw biogas can be “upgraded” (cleaned) to produce biomethane of pipeline quality, or converted into compressed natural gas (CNG; 90% CH4) or liquefied natural gas, displacing traditional refined fossil fuel products. Biomethane also offers a possible route to bio-based synthetic jet aircraft fuel and various petrochemical products [Scurlock, 2017]. The U.S. DOE estimated only about 2000 facilities in place in 2015, with at least 11,000 possible biogas production facilities at U.S. farms, wastewater treatment plants, and landfills [AFDC, 2017; US DOE Biogas Opportunities Roadmap].

 

Other GHGs include nitrous oxide (N2O), water vapor (H2O), ozone (O3) and synthetic chemicals known collectively as fluorinated gases (CFCs and HFCs). See the “Biogas Web Resources” link for more information about GHGs.

 

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