Wasting the Nation.indd - Groundwork

Chapter 5: Modernising municipal wasteKnowledge of this process challenges the idea that landfills can really be isolated fromthe environment. The waste body produces water from chemical processes and is alsoinfiltrated by rainwater. The water picks up various contaminants to turn into the‘landfill soup’ known as leachate. It is supposed to be treated and then disposed to themunicipal sewage works. In South Africa, most leachate is not treated.Gases – some smelling foul and others odourless but dangerous – must also escape thewaste body. Landfill gas was until recently simply seen as a threat, mainly because themethane is explosive. In 1986, a gas explosion at the Loscoe dump in the UK – in anold clay quarry that had been filled and then capped – blasted a house 70 meters awayand injured the three occupants. Damage to local vegetation indicated high landfillgas concentrations and potential danger before the blast. Landfill gas managementsolutions are passive venting (which really means just letting the gases escape) or a gasremoval system feeding gas either to a flare or for use as energy.Materials used to contain the waste body – clay caps on top and liners at the bottom –are subject to stresses from the movement of the waste body as waste decomposes andcompacts. Liners may also tear, be eaten by acidic or caustic agents, or be punctured bysharp objects or burrowing animals. The liners are designed to last 50 years. In SouthAfrica, new landfills are planned for 20 to 30 years’ operation with a 30 year aftercareperiod. At the end of this period, the liner is expected to fail. This does not mean,however, that the waste body will no longer be polluting.Box 20: What’s in landfill gasLandfill gas (LFG) is between 40 and 60% methane, with most of the rest beingcarbon dioxide. It contains varying amounts of nitrogen, oxygen, water vapour,sulphur and hundreds of other contaminants, mostly (non-methane) volatileorganic compounds (VOCs) but sometimes also metals such as mercury.VOCs usually make up less than 1% of landfill gas. The US EPA has identified 94in LFG although other tests have found many more. They include benzene, toluene,chloroform, vinyl chloride, carbon tetrachloride, and trichloroethane. At least 41on the EPA’s list are halogenated compounds – containing chlorides, fluorides andbromides – which give rise to dioxins and furans when LFG is burnt either in flaresor for energy.Source: Mike Ewall, Energy Justice Network.- 132 - groundWork - Wasting the Nation