Carbon offsets from organic waste conversion projects


The Climate Act ion Reserve (the Reserve) has long had a protocol to give credit for the capture and destruction of methane emissions from organic waste in landfills, but they have now opened up the possibility of credits for projects that prevent that waste from entering landfills in the first place. In October 2009, the Reserve adopted the Organic Waste Digestion Project Protocol, covering both municipal food waste and agro-industrial wastewater. In December, they kicked off development of the Composting Project Protocol, due to be completed and adopted in June of 2010. Many municipalities have become interested in diverting organic waste from landfills to other technologies for waste conversion, but these can be expensive enterprises. Carbon offsets can provide an important revenue stream to help finance these projects.

Organic Waste Digestion (OWD)
Anaerobic digestion is not a new technology, but it has been enjoying a renaissance as more people are realizing the benefits, and advances have been made in digester design and operation. The OWD protocol outlines eligible waste streams, including MSW (municipal solid waste) food waste and agroindustrial wastewater, and also provides requirements for monitoring, metering and verification.

Post-consumer food waste makes up about 12.5 percent of all MSW nationwide, and only about 2.6 percent of this is currently diverted from landfill. In the landfill, organic waste decays over time and releases methane as landfill gas (LFG). Methane is a potent greenhouse gas—21 times more potent than carbon dioxide in our atmosphere. It can also pose a threat to local groundwater by migrating out of the landfill. When MSW food waste is diverted to an anaerobic digester, the project generates credits based on the avoided emissions from landfills.

The OWD protocol takes a standardized approach, assuming that the food waste would have been sent to a landfill, and that all landfills have gas collection systems that reach the waste after it has been in the landfill for three years. A first order decay (FOD) model is used to calculate how much methane would have been generated by the specific amount of food waste over time. Since the crediting period for landfill projects is 10 years, each calculation is for 10 years’ worth of decay in the landfill, minus what would have been destroyed in the LFG collection system. The protocol credits digestion of non-industrial food waste such as uneaten food, food scraps, spoiled food and food preparation wastes from homes, restaurants, kitchens, grocery stores, campuses, cafeterias and similar institutions. Industrial food waste such as solids from food processing facilities generally still has a use value and is not typically disposed of in a MSW system.

Agro-industrial wastewater streams are generally eligible if they originate from a privately-owned treatment facility, and have a baseline management system that uses uncontrolled anaerobic treatment (usually a lagoon or open tank at least one meter in depth). The waste streams are then diverted to a closed, anaerobic digester to allow for collection and destruction of the methane gas. Credits are based on the characteristics of the particular waste stream, using periodic sampling of chemical oxygen demand (COD) to model the avoided baseline emissions. Excluded sources include municipal wastewater, pulp and paper mills, breweries, ethanol plants and pharmaceutical production facilities.

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