Want to cut your energy bill? There's an ass for that. Donkey dung produces methane ideal for heating and lighting in rural areas, says a team from the physics department at Fort Hare University.Their findings are part of a push involving six government departments and the private sector to make "biogas" part of the energy solution for rural communities with no electricity - but plenty of manure.Mark Tiepelt, chairman of the Biogas Association of SA, said the 80 delegates who attended a gathering this month of the National Biogas Platform saw huge potential to create energy and jobs, and to reduce waste and carbon emissions.Biogas is produced when organic waste decomposes in the absence of oxygen. Methane, which can be used as fuel, and carbon dioxide, are produced and the solid waste left is a high-quality organic fertiliser.But an off-the-shelf plastic model which can digest 25kg of organic waste daily costs about R10500. Tiepelt said an underground digester for a rural community, plus pipework and methane-fuelled stoves and lights, would cost about R40,000...