Figure 4 Feedstock for and output from anaerobic digestion
Source: (EPA, 2021 )
are less common in the UK, whereas in Germany, in 2014, nearly 8,000 aerobic digesters were operating, generating 4,000 MWe electricity. Project Drawdown estimates that large anaerobic digesters could grow from current values of 0.7% or 100 TWh of global electricity generation to as much as 1.7% or 761 TWh by 2050 and reduce total GHGs by 9.8 GT of CO 2 eq (Drawdown, 2019c). At present, there are only five Bioenergy with Carbon Capture (BECCs) facilities operating globally (Global CCS Institute, 2019). Equipping biogas to power plants with carbon capture would result in reductions in both methane and CO 2 emissions. Methane capture from landfill The world generates 2.01 billion tonnes of MSW annually, an average of 0.7kg per person per day, ranging from 0.11 to as much as 4.54kg. By 2050, global waste is expected to grow to nearly 3.4 billion tonnes (see Figure 5 ) (World Bank, 2022).
In 2019, landfill accounted for 12% of the world’s total methane emissions. Globally, most waste is disposed of in some form of landfill, but only 8% is disposed of in sanitary landfills with landfill gas collection systems (World Bank, 2022). The technology to capture biogas from landfill is relatively simple. Dispersed, perforated tubes are inserted at a suitable depth to collect the gas, which is piped to a central collection area. The gas can then be compressed and purified for use as fuel or mixed into the natural gas supply. Project Drawdown estimates that capturing and using landfill methane for electricity generation can result in emissions reductions equivalent to 2.2 Gt GHG emissions by 2050 (Drawdown, 2019d). Clearly, reducing the amount of hydrocarbon waste that ends up in MSW will reduce methane emissions from landfill. The use of anaerobic digesters has already been discussed. Composting household and garden waste should be encouraged as another option that averts
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