About 37% of waste produced globally goes to landfill; another 31% is simply dumped, whilst 19% is recovered through recycling or composting, and 11% is burnt . Let’s focus on landfill – huge holes in the ground filled with rubbish . When organic matter (food, plants, paper etc.) sits in landfill, it is broken down by tiny bacteria and fungi which release a lot of methane in the process .
Methane is a much more potent greenhouse gas than carbon dioxide, although it stays in the atmosphere for a shorter time . Globally, landfills are the third biggest source of methane emissions from humans, after energy generation and livestock [3,5,6].
What can we do about these emissions? One option is to capture the methane, together with other ‘landfill gas’ . This can be done by sucking air out of wells in the landfill site, a bit like using a vacuum cleaner ! The landfill gas can then be used instead of conventional natural gas to generate electricity . Although it produces only about half as much heat per litre of gas, it is a reliable source of energy that can be produced 24 hour per day (unlike wind and solar) [3,7].
Another environmental problem caused by landfills is that liquid contaminated with waste can leak out from the bottom of the pit . This can enter underground water (groundwater), in turn contaminating water supplies for people [8,9,10]. Landfills that are properly lined, however, should be able to avoid this problem [8,11].
In the next few posts we’ll look at how we can reduce the negative impacts of landfill by producing less waste in the first place , and how we can avoid landfill by using waste to generate energy for human use .
 https://datatopics.worldbank.org/what-a-waste/trends_in_solid_waste_management.html See: Globally, most waste is currently dumped or disposed of in some form of a landfill
 https://www.globalmethane.org/documents/landfill_fs_eng.pdf See: What is landfill gas; Figure 1; converting LFG to Energy
 https://pubs.acs.org/doi/pdf/10.1021/es400399h See: Figure 2
 https://www.globalmethane.org/documents/gmi-mitigation-factsheet.pdf See: Figure 1 (coal mining and oil & gas combine to represent energy generation)
 https://www.sciencedirect.com/science/article/pii/S1364032114002366 See: Introduction
 https://www.sciencedirect.com/science/article/pii/S0043135412002771 See: Introduction
 https://www.sciencedirect.com/science/article/pii/S0301479718305644 See: Abstract
 https://www.theccc.org.uk/wp-content/uploads/2013/04/Waste-factsheet.pdf See: What can be done to reduce emissions in this sector?
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