A household disposes of 300 kg of domestic waste a year, 90% of which is carbohydrates and 10% of which is inert, in an anaerobic digester. The family uses methane for cooking on an open fire. Estimate the number of litres of water that could be boiled annually.

*Speficic heat of water: 4.2 kJ kg-1C-1

*Assume that efficiency of heat conversion to water from the biogas to be 38% and that the starting temperature of the water is 40 degrees Celclius. The latent heat of vaporization of water is 2,260 kJ/kg.