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A comprehensive investigation was conducted to evaluate the efficiency of newly installed biogas digesters in saving biomass resources and addressing energy squandering. Compared with traditional coal-based or firewood dominated energy consumption, the biogas digesters economize on energy resources due to higher heat efficiency. Furthermore, since crop residues of straw and other domestic animal and human excreta are effectively recycled and reused as anaerobic fermentation materials of biogas digesters, greenhouse gas emissions are significantly reduced by converting the previous extensive combustion of such into a sustainable and highly efficient practice in the rural region. The results in this study show that total energy consumption is 412 kgce (kgce: 1 kg standard coal. 1 kgce = 29.31 MJ) in Xiyang Township in 2009. The construction of biogas digesters significantly contributes to the transformation of rural household energy consumption structure, though biogas as a renewable energy only accounts for 6.31% of the total household energy consumption. Per capita rural household energy consumption is 393.07 kgce in household with biogas digesters and 437.60 kgce in household without biogas digesters. In addition, application of biogas dregs, slurry, and marsh liquid to the agricultural crops have greatly reduced the expenditure of buying chemical fertilizers. The average commercial fertilizer per mu (0.067 ha) in rural households using biogas digesters is 12.43 kg and the cost per mu is 29.53 yuan (1 yuan = 0.1523 dollar), while rural households without biogas digesters use 25.22 kg of commercial fertilizers and cost 59.71 yuan per mu.

The utilization of biogas in rural semi-arid regions of China is a potentially clean development mechanism (CDM) and has profound implications for applied energy. (C) 2011 Elsevier Ltd. All rights reserved.