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With the rising demand for renewable energy and environmental protection, anaerobic digestion of biogas technology has attracted considerable attention within the scientific community. This paper presents a comprehensive review of research achievements on anaerobic digestion developments for biogas production. The review includes a discussion of factors affecting efficiency (temperature, pH, C/N ratio, OLR and retention time), accelerants (greenery biomass, biological pure culture and inorganic additives), reactors (conventional anaerobic reactors, sludge retention reactors and anaerobic membrane reactors) and biogas AD processes (lignocellulose waste, municipal solid waste, food waste, livestock manure and waste activated sludge) based on substrate characteristics and discusses the application of each forementioned aspect. The factors affecting efficiency are crucial to anaerobic digestion, because they play a major role in biogas production and determine the metabolic conditions for microorganism growth. As an additive, an accelerant is not only regarded as a nutrient resource, but can also improve biodegradability. The focus of reactor design is the sufficient utilization of a substrate by changing the feeding method and enhancing the attachment to biomass. The optimal digestion process balances the optimal digest conditions with the cost-optimal input/output ratio. Additionally, establishment of theoretical and technological studies should emphasize practicality based on laboratory-scale experiments because further development of biogas plants would allow for a transition from household to medium- and large-scale projects; therefore, improving stability and efficiency are recommended for advancing AD research. [ABSTRACT FROM AUTHOR]

Abstract: With the largest population living in rural areas, the lack of clean energy supply is an important problem in China, and the utilization of renewable energy not only meets the demand of energy, but also provides a basis for environmental protection and sustainable development. This paper reviews use of clean energy in a resource-rich region, including the basic principle of the development of recycling agriculture, the potential, the present status and the future of renewable energy in the region rural areas. If the project will be finished, there will be 300,000 families benefiting from it and it can bring at least 2.2×108 US dollars revenue increase directly, the indirect revenue increase will be 0.15billion US dollars, the environment will be improved and the living standard in Jincheng''s rural areas is also be greatly improved because of developing biogas project. Based on the developing status and constraint conditions, the solutions to further promote renewable energy projects in this region are also proposed. [Copyright &y& Elsevier]