Evaluation and analysis of net emergy yield of two bio-energy stations in Beijing suburb

Based on emergy method, the paper evaluated emergy input and output of middle straw gasification stations and biogas stations in Beijing suburb. The results showed that the net emergy yield ratio of straw gasification was higher than that of biogas station, and they were both lower than 1, which indicated that they both had a lower efficiency and no stronger economic competitiveness. So the development mode of two kinds of energy was uneconomical and unreasonable due to technical restriction. We should have a better understanding of the development mode of biomass energy, especially the development mode of the big or middle biogas stations. It should be constructed suitably according to the local conditions and lay emphasis upon the enhancement in research, meanwhile, it should also lay emphasis upon the commonweal characteristic of the bio-energy and exploit adequately the potential of biomass resources in Beijing suburb.