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Carbon Offset and Value Opportunities for Airports 15 In the United States, generally recognized project types can be broken into three main cate- gories: (1) methane capture and destruction; (2) land use changes to sequester carbon dioxide; and (3) the destruction of industrial pollutants which are high global warming potential GHGs. Each project type presents unique challenges to airports, making feasibility of many of the most common offset project types unlikely as viable options for airports. The following is a descrip- tion of the types of projects that generally fall into these categories and an exploration of an air- port's potential to participate. 2.1.1 Airport Offset Project Applicability Despite the growing categories of recognized offset projects, an airport's ability to participate in activities recognized by the leading offset standard bodies is currently limited. The types of GHG emission reduction projects that airports typically engage in do not align with many of the traditional offset program types recognized by U.S. offset protocols. Table 4 describes some potential project types that may be applicable to airports, based on typical airport operations. The following sections summarize common offset project types. 2.1.2 Methane Destruction Methane (CH4) gas capture and destruction is a recognized project type by most offset stan- dard bodies. The requirements vary to some degree, but are generally two-fold: (1) capture of landfill gas (made up largely of methane gas) and (2) destroy through combustion the methane in landfill gas (De la Cruz 2010). Table 4. Offset projects and airport applicability. Project Type Project Description Airport Feasibility Notes Landfill Gas Install equipment to capture Potentially viable if airport landfill is currently in methane gas from a landfill; operation. Closed landfills can produce gas for destruction could yield a approximately 10 to 30 years. usable energy source. New landfills pose a safety risk at airports and are prohibited, as specified in FAA Advisory Circular 150-5200-34. Enhanced Install equipment at airport Subject to an airport having a wastewater Wastewater wastewater treatment plant treatment facility on-site. Treatment to capture methane gas from wastewater. Organic Waste Collect food waste in airport Examples of airports diverting organic waste Composting terminal and send to a from landfills to composting facilities have composting site for included Los Angeles, Oakland, Portland, and methane capture. Seattle International Airports. Forestry Restore vegetation, avoid Forest that attracts wildlife is a risk to airport conversion of vegetation to operations and safety. On-airport wildlife commercial development, issues could be potentially avoided through or add vegetation to airport careful selection of the appropriate type property. (grass, bush, or tree) and location (landside, remote airport property) of vegetation. To be creditable, a reforestation project would likely need to be additional to environmental mitigation requirements stemming from a regulatory decision. Refrigerants Switch to less GHG-intense GHGs from refrigerants likely make up only a refrigerants. small fraction of airport emissions.

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16 The Carbon Market: A Primer for Airports Key Takeaways for Airports The primary opportunity for a methane destruction offset project would be from an existing landfill on airport grounds. New landfills are prohibited at airports, limiting the applicability of this offset project type moving forward. In its Inventory of U.S. Greenhouse Gas Emissions and Sinks: 19902008 study, the EPA es- timates that methane emissions make up about 9% of all GHG emissions in the United States (EPA 2010). There are a variety of methane emitting sources in the United States; however, the leading sources are enteric fermentation (digestion from livestock), landfills, natural gas systems, coal mining, manure management (from livestock), petroleum systems, and wastewater treat- ment. Figure 2 presents more information on the relative contribution of these methane sources. Operators of these various sources of methane gas have developed methods for capturing the gas by installing a system of wells, pipes, blowers, caps, and other technologies. After capture, methane is combusted and destroyed, usually by a flare or a boiler which combusts the gas in order to create heat for other processes such as electricity generation. When methane is com- busted, the gas is destroyed and the byproduct of combustion emitted is carbon dioxide (CO2) which has a much lower GWP. The result is a lower impact to GHG concentrations in the atmo- sphere compared to methane seeping into the atmosphere directly from the landfill or other methane source. The following are sources of methane emissions that are recognized by U.S. off- set standards bodies to generate offset credits. Landfills--Landfills remain the most common method for disposing of waste in the United States and a potential, albeit unlikely, methane capture and destruction project source for air- ports. The bacterial decomposition of solid waste in a landfill creates a landfill gas, which is pri- marily comprised of two GHGs: methane and carbon dioxide. With time--and if not collected, captured, and/or destroyed--landfill gas can be released into the atmosphere, adding to the over- all concentration of GHGs. If captured, landfill gas can potentially serve as an energy source. Wastewater Other 7% Enteric Treatment Fermentation 4% (Livestock Petroleum Systems Digestion) 5% 25% Manure Management 8% Coal Mining Landfills 12% 22% Natural Gas Systems 17% Source: US EPA. Inventory of U.S. Greenhouse Gas Emissions and Sinks: 19902008. Washington, D.C., 2010. Figure 2. U.S. methane emissions by source (average 19902008).