China's fast-growing cities will no longer be able to cope with the amount of rubbish they produce by 2020, according to a government study. By that time the garbage produced annually by urban households and businesses in the world's most populous nation will reach 400m tonnes, equivalent to the figure for the entire world in 1997, the China Daily reported. It cited research by the China Council for International Cooperation and Development, a government environmental watchdog, which warned that inadequate waste management could result in methane explosions, the release of toxic gases and the pollution of water supplies.