Landfill gas recovery

A main factor in reducing methane emissions from the landfill body is to collect the landfill gas before it is released into the atmosphere. For this reason landfill gas recovery systems are applied: LFG is extracted from the landfill body using a series of wells. A vacuum system directs the collected gas to a point where it is processed.

Several types of processing are possible. In the case of a flare only the gas is burned so that its energy content is lost. Alternatively the gas can be used beneficially; this includes the use of the gas as fuel in energy recovery facilities, such as internal combustion engines, gas turbines, micro-turbines, steam boilers, or other facilities that use gas for power production. By this means up to an average of 70 percent of the gas generated can be captured and transformed into electricity and heat.

Besides direct avoidance of greenhouse gas emissions, LFG recovery prevents greenhouse gas emissions caused by the fossil fuel which would be needed for production of the equivalent of electricity and heat.

Some examples may illustrate the application of landfill gas recovery systems and its effects in the case of the USA, and of Mexico as a developing country:

• In the USA the national landfill gas budget accounts for 24 percent of all anthropogenic methane emissions; annual total was 126 Mio t CO2-eq. by 2006 (EPA, 2008a). The emissions stem from 1,800 operational landfills. From 1990 to 2005 landfill gas emissions decreased by 18 percent. This downward trend is the result of increased gas collection and combustion intensity. In 2007, 435 landfill gas projects were active which had a capacity of 1,325 MW. These projects provided over 10.5 billion kWh of electricity, and delivered to corporate and government users landfill gas with an energy equivalent to powering roughly 800,000 homes and heating more than half a million homes each year (EPA, 2008). About 1,530 landfills with a capacity of 1,290 MW are candidates for landfill gas programmes coming into power in the next few years (EPA, 2007d). A recent example supported by EPA was a set of 22 landfill gas projects operated by a landfill company in New England. These projects will generate in excess of 110 MW of renewable energy (or equivalent). They remove from the atmosphere over 0.6 Mio t CO2-eq. each year which is equivalent to planting in excess of 1.1 million acres of trees and offset the need for almost 21,000 rail cars of coal (EPA, 2008).

• In developing countries national as well as international programmes support the establishment of landfill gas recovery systems to reduce methane emission and use the energy for power production or household lightening. The following example is from Mexico, where landfills contribute to 10 percent of the total human-influenced greenhouse gas emissions. It demonstrates the possible effects (Simeprodeso, 2007): Beginning in 2001 in the city of Monterrey with nearly 4 million inhabitants, where over 4,500 t of municipal solid waste are disposed per day in the Simeprodeso landfill, methane from the landfill was harnessed for energy recovery while reducing methane emissions. A joint venture between government and business interests, which in part was funded by an US$ 5 Mio grant from the Global Environmental Facility, launched a project for transforming LFG into electricity. The energy is fed into the local net to help drive the public transit system by day, and light city streets by night, and to provide power for over 15,000 homes. It is planned to enhance the capacity of the existing power station, so that 80 percent of the municipal government's electricity needs will be met. Moreover, as the Simeprodeso landfill continues to expand, LFG generation is estimated to increase to fuel a 25 MW facility for completion by 2016.

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