862 K.Li et al.Renewable and Sustainable Energy Reviews 54(2016)857-865 plants [131.The polices for the development of biogas is normally 8.2.Recommendations for future work general guideline however more detail measures are needed. The development of biogas industry should consider the fol- The benefits of biogas technology have already been remark- lowing respects.At first,financial support for the constructions of ably known in China,such as energy capture from organic waste. super-large scale biogas plants for bio-natural gas production environment protection.less dependency on fossil fuels,reducing should be emphasized by the government.According to National greenhouse gas emissions,etc.,while its development is full of Biogas Project Plan in 2015,in 2015,2 billion RMB Yuan will be challenges.The problems are mainly related with technology. invested by Chinese government to support super-large scale More specifically,there is a shortage of technical support for high- biogas plants as a priory.In addition,the functions of biogas plants efficiency gas production.In addition,the extension and policies in balancing development between farm breeding and planting for biogas technology are also proposed.To accelerate the devel- should be improved in order to develop eco-cycle-agriculture. opment of biogas technology,a great attention should be paid to Further more,standard and management information platform of the following aspects in future: biogas plant should be further established.Finally.the policy for biogas technology should be easily operated and be long term (1)Biogas plants with diversified feedstock materials should be effective in order to promote the development of biogas promoted.In regards of the nutrient imbalance in mono technology. substrate anaerobic digestion,optimum C/N ratio and reduced relevant toxicity can be obtained by adding alternative mate- rials to single substrate 8.Conclusions and recommendations for future work (2)To improve the hydrolysis rate of straw materials,studies about finding suitable disintegration methods need to carry 8.1.Conclusion out in respect of combined pretreatment methods which are reported as effective,economical and eco-friendly.In addition, The anaerobic methane fermentation is an effective technology harvest time of biogas crops should also be considered since for the energy conversion and resource recovery of agricultural lignin content increased during their progressive maturity. residues.Due to its economical and renewable advantages,biogas (3)More appropriate biogas process technologies and reactors as a suitable substitution for fossil fuels,has attracted the attention need to be explored according to anaerobic digestion char- of the world.Researches demonstrated that biogas yield of bio- acteristics of substrate materials such as the crust forming and mass materials could be improved by adjusting C/N ratio of feed- outputting problems of straw,and the fast acidification pro- stock,controlling fermentation conditions and using various pre- blem of FVW. treatment methods.etc.Conducting such researches are very (4)Financial support for the constructions of super-large scale biogas plants for bio-natural gas production should be empha- important to provide theoretical basis for the operation of biogas sized by the government. plants.In addition,the industrialization of biogas needs to be (5)The development of biogas electricity generation and vehicle developed further.In brief,main conclusions are as follows: biogas should be emphasized.Only in this way could the utilization of biogas be efficient and diverse. (1)Effects of temperature,ammonium etc.on methanogens were (6)To promote the commercialization of biogas technology,the compared.The ammonium/acetate sensitive Methanosaeta financial subsidies for biogas should be given not only to were almost absent at 55-60C,which may suggest an biogas project constructions but also to biogas products and effective way to improve the process stability by digestion at follow-up services.Meanwhile,standards and regulations for 55-60C to exclude more stress susceptible acetotrophic quality control,inspection and evaluations need to be carried methanogens. out strictly. (2)To improve the biogas yield,pretreatment of feedstock materials like C/N ratio adjusting,disintegration and grinding are necessary in order to make substrate nutrition balance and Acknowledgments degraded easily. (3)The co-digestion of livestock manure with low nitrogen Financial support from National Natural Science Foundation of biomass can generate higher methane yield than the mono- digestion of cither manurc or bio-solid wastc like straw,grass China through contract(Grant no.51376121)is greatly acknowledged. silage and FVW. (4)Methanogenesis is the rate limiting step in the anaerobic digestion of cellulose-poor wastes like FVW due to the rapid References acidification of these waste.Therefore,other feed stocks or alkaline buffer should be added to FVW. 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