The Climate and Clean Air Coalition (CCAC) has released a report titled 'Reducing Methane Emissions from Landfills: The potential of biocover systems'. Biocovers are microbial layers in which naturally occurring bacteria convert methane into less harmful carbon dioxide and water. The report says they can cut up to 50% of landfill methane emissions over the long term while improving air quality and public health. Landfills produce about 11% of global human-made methane, a gas with very high global warming potential.