US researchers say agricultural waste from coconut and mango farming could generate significant amounts of off-grid electricity for rural communities in South and South-East Asia.    Many food crops have a tough, inedible part which cannot be used to feed livestock or fertilise fields. Examples of this material — known as \'endocarp\' — include coconut, almond and pistachio shells, and the stones of mangoes, olives, plums, apricots and cherri Endocarp is high in a chemical compound known as lignin. High-lignin products can be heated to produce an energy-rich gas that can be used to generate electricity. The researchers identified high-endocarp-producing regions of the world — and noted that coconut and mango agriculture account for 72 per cent of total global endocarp production. Coconut production alone accounted for 55 per cent. Most coconut endocarp comes from South and South-East Asian countries, including Bangladesh, Laos, Malaysia, Myanmar, Thailand, and Vietnam. They then overlaid these findings with energy consumption data to identify communities with little access to electricity, who could benefit from endocarp-based energy.