bio-gas development procedure in iran and the world

because every day production of refuse material is increasing, interest in the development of biogas units in many countries, both as traditional and industrial plants, has been increased. about 74 million tons of methane gas is produced from cattle dung and 40 million tons is produced only from urban solid wastes in the world annually .this would influence the greenhouse effect india and china have made significant studies in the use of biogas as a source of energy for rural areas since 19308. these units which are known as 1hinese model and indian type have been considered to be compatible with rural requirements. in iran there have been some studies by 16 research organisation and universities from 1975 which until now about 60 units have been installed. in this paper with attention to historical records of biogas production utilization, the develoment of biogas in iran and the world, is discussed, and guidelines for the modification and development are suggested