National Geographic : 2014 Jan
U.S. METHANE EMISSIONS by source 37.5%* Natural gas and petroleum industry 21.5% Animal digestion 16% Landfills 2% Wastewater treatment 5% Other 8% 11% Coal mining Manure storage O2 O2 O2 Acetate Acetate Acetate Acetate CH4 Methane CO2 Carbon dioxide O2 Cover vegetation Topsoil Protective cover soil Drainage layer Liner Compacted clay Daily cover material Waste Collection layer for liquid waste from organic breakdown Filter Transport system for liquid waste from organic breakdown Liner Compacted clay Foundation Waste HARNESSING GAS Gases produced when trash breaks down are piped to the surface by wells. The methane is burned to generate electricity or is used as fuel. TURNING WASTE INTO ENERGY Trash isn’t worthless. When it decomposes, it produces methane, which can be converted into electricity. JASON TrEAT, NGM STAff GrAPHiC: THOMAS POrOSTOCky SOUrCES: EPA LANdfiLL METHANE OUTrEACH PrOGrAM; GrEG ENTErLiNE ANd LyNN BrOWN, WASTE MANAGEMENT *Percentages do not add up to 100 because of rounding. As the waste breaks down, bacteria remove oxygen. As it mixes with trash and air, organic waste begins to decompose. Other bacteria that thrive without oxygen produce acetate, a relative of the acid in vinegar. Additional bacteria convert acetate to carbon dioxide and methane.