Progress has been made in the key technologies for straw biogasification by the Li Xiujin team

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Our country has made progress in straw biogasification technology and acquired key technologies with independent intellectual property rights. This technology, developed by a research team from Beijing University of Chemical Technology, can not only address the problems of air pollution and traffic safety caused by the open-burning of large amounts of straw, but also produce clean renewable energy. Our country is the largest agricultural producer in the world, generating about 700 million tons of crop straws each year. Approximately 50% of this amount is not properly processed or utilized, which not only results in a waste of resources but also leads to severe air pollution due to the widespread burning of these straws. This in turn causes fires and affects the safety of highway and civil aviation operations. The treatment and utilization of straw have become one of the major environmental problems in China. However, due to the lack of economically viable technologies, issues related to banning the burning of straw and its large-scale utilization are difficult to resolve for the time being. On the other hand, driven by **, rural biogas in China has seen rapid development in recent years. By the end of 2008, over 30 million household biogas digesters had been installed across the country, and more than 3,000 large and medium-sized biogas projects for livestock and poultry farming had been built. By 2010, it is planned that there will be 40 million household biogas systems in our country, along with over 6,000 large and medium-sized biogas projects. This raises the issue of raw material supply. At present, the main raw material for biogas production in our country is livestock and poultry manure, which is unable to, nor sufficient to, ensure the supply of raw materials and the achievement of the aforementioned goals. Using straw as a raw material to produce biogas not only opens up new avenues for the utilization of straw, helping to address the environmental pollution and resource waste caused by straw burning, but also solves the problem of raw material availability for the large-scale adoption of biogas, achieving two benefits at once. Furthermore, compared with existing straw pyrolysis and gasification technologies, biogasification offers the advantages of mild reaction conditions, high calorific value of biogas, and good quality, while also producing no wastewater, tar, or biogas residue. The straw “biogasification” technology is what is commonly referred to as “anaerobic fermentation” technology. It converts organic materials such as straw into biogas through the digestive action of microorganisms under anaerobic conditions. Biogasification technology has been widely used for the treatment and energy conversion of human and animal manure, food waste, and organic household waste. However, due to the high lignocellulose content, low digestibility, and low gas production of straw, it is generally not possible to produce biogas solely from straw as a raw material. A research team led by Professor Li Xiujin from Beijing University of Chemical Technology has been conducting research in this area for over 10 years, making progress in the key technologies for straw biogasification. To address the issues of high lignocellulose content in straw, its difficulty in being digested by anaerobic bacteria, low gas production during anaerobic fermentation, and poor economic viability, they developed a chemical pretreatment technique at room temperature and in solid form. This technique allows for rapid chemical treatment of straw prior to anaerobic fermentation, converting it into a form that is easier to digest; as a result, gas production from straw can increase by 50% to 120%, thereby creating the conditions necessary for large-scale biological gasification of straw. Furthermore, to address issues such as the low density, large volume, lack of fluidity of straw, and poor heat and mass transfer efficiency, they developed a new type of reactor. This reactor features a combined enhanced stirring system, which enables mechanical feeding and discharging as well as automated and efficient stirring. At the same time, the use of a semi-underground reactor structure with solar greenhouses allows part of the solar and geothermal energy to be converted into biogas energy, **improving the system’s energy conversion efficiency and energy efficiency ratio. At present, chemical pretreatment and high-efficiency reactor technologies have obtained **patented inventions, with independent intellectual property rights in China. Using this technology, China’s first centralized biogas production demonstration project based solely on straw as raw material was established in Tai’an, Shandong in 2003, providing energy for household use to 160 farming households ； Two more projects were built in 2007 in Shunyi, Beijing, and in 2008 in Dezhou, Shandong, capable of providing clean energy to 300 and 375 rural residents respectively.