Investigations and Reflections on the Industrial Development of Straw Biogas

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　Investigations and reflections on the development of straw biogas industrialization. I. Why is it necessary to develop straw biogas? 　　1. Abundant raw material resources. There are over 1.8 billion mu of arable land across the country; with 0.5 tons of straw produced per mu, that amounts to 900 million tons. Including the straw produced around rural households nationwide, the total amount surely exceeds 1 billion tons. What a huge amount of resources this is. Half of agricultural inputs are used to produce fruits, while the other half is used to produce straw. Studying the nature of straw is essentially addressing the issue of “reclaiming the other half of agriculture”. This is of great significance for addressing the issues related to agriculture, rural areas, and farmers. 　　2. Urgent real-world needs. **In the 2016 **work report, the Prime Minister stated that it was necessary to increase the supply of natural gas, improve policies to support the development of wind energy, solar energy, biomass energy, and other forms of clean energy, in order to raise the proportion of clean energy. Encourage the resource utilization of straw to reduce direct burning. Developing straw biogas can not only increase the supply of biomethane and raise the proportion of clean energy, but also significantly reduce direct burning; it is a viable measure that addresses multiple urgent practical needs at once. 　　3. Biogas production from straw features high energy and material efficiency. Under modern technological conditions, the biogasification or methanization of straw enables the production of high-quality biomethane, while allowing the maximum amount of plant nutrients to be retained and returned to the soil. The biogasification process is a key element in the material cycle and utilization within agricultural ecosystems; it represents the main method for making use of crop straw resources. It constitutes an efficient way of tapping into potential resources, offering good economic benefits and environmental advantages, and it is the only negative-carbon biomass energy source. 　　II. The development history of straw biogas For a long time, straw has been a challenge as a raw material for biogas production in China. Many experts and scholars from domestic colleges, universities, and research institutions have devised various methods and carried out extensive research and experiments on the pretreatment of straw. Some advocate chemical pretreatment, some prefer spray blasting pretreatment, some recommend silage pretreatment, and others suggest pile composting pretreatment – it’s truly a diversity of approaches competing with one another. 　　Yao Xuhua, a farmer from Qingxian County who is 64 years old this year, has spent over 40 years researching straw biogas. In 2006, his research made a significant breakthrough: he used pure corn straw, which, after being simply chopped up, could be used in biogas digesters to produce gas effectively. Zhao Chaoying, who was the county party secretary at the time, handled matters on the spot, describing straw biogas as \"China’s fifth great invention.\" He ordered the county finance department to allocate 200,000 yuan, and also coordinated with the local villages to provide land in order to support this new innovation. From July 15 to August 31, 2007, the Biogas Research Institute of the Ministry of Agriculture conducted on-site monitoring of the operation of the newly built straw-based biogas project in Qing County. On September 3, an expert panel was formed, with Researcher Yan Li as the team leader, Section Chief Li Jingming as the deputy team leader, and Researcher Mei Zili, Researcher Fu Zhengge, and Associate Researcher Zhao Yuexin as members. The panel issued an evaluation opinion stating that “the operational data of the project are detailed and reliable; the gas production rate per unit volume of the digester reaches 1.1 m³/m³·day, and approximately 0.5 m³ of biogas can be produced from every kilogram of straw fed into the system. The technology employed in this project has reached a practical level of operability and can thus be widely promoted.” 　　In 2009, the Ministry of Agriculture established sixteen straw biogas pilot projects across the country. In 2010, the Ministry of Agriculture allocated 31 straw biogas pilot projects across the country. 　　The straw biogas project in Qingxian County has attracted the attention of domestic universities, research institutions, and enterprises; over the years, countless scholars have come to visit and study there, which has contributed to the rapid development of straw biogas usage across the country. Qingxian County has also established a biomass company dedicated to carrying out technical development work. On June 26, 2012, an appraisal committee headed by Zhao Lixin, director of the Institute of Planning and Design of the Ministry of Agriculture and also head of the Institute of Energy and Environmental Protection, with Li Jingming, secretary-general of the Chinese Biogas Society, serving as deputy chairman, conducted an evaluation of the project titled “Research on the Process Technology for Producing Biogas through Moderate-Temperature, High-Concentration Fermentation of Straw and the Development of Related Equipment” in Qing County. The committee concluded that this project was the first of its kind in China, filled a gap in domestic research, and reached a leading level in the country. 　　In 2015, the central government allocated 2 billion yuan to support 25 pilot projects for large-scale biomethane production and 386 large-scale biogas projects nationwide. **The General Offices of the National Development and Reform Commission and the Ministry of Agriculture also issued the \"Work Plan for the Transformation and Upgrading of Rural Biogas Projects in 2015\". In the same year, the **Energy Bureau launched a pilot project in Inner Mongolia to produce 200 million cubic meters of biogas per year. Straw is the main raw material for producing biogas. 　　**Although it has been ten years since the relevant departments began to promote Yao Xuhua’s straw biogas technology across the country, it is still in its initial stage of development; in other words, it is on the verge of making a major breakthrough in terms of industrialization. It represents a strategic emerging industry with a market value of 400 to 500 billion yuan. It’s only a matter of time before the industrialization of straw biogas evolves into the industrialization of biomethane. 　　III. Main problems in the development of straw biogas 1. Poor economic viability of investment. It is mainly characterized by large investment, small scale, low output, and low income. According to rough estimates, since 2003, our country has allocated several billion yuan each year to subsidize farmers for biogas production and so-called biogas projects. Including this year’s 2 billion yuan, the total has reached over 40 billion yuan. After so many years of effort, biogas has still not developed into a viable industry in our country. What causes this situation? Some authoritative experts believe that it is mainly a matter of guiding principles. People often consider biogas to be an industry that provides public benefits and welfare, and they tend to rely on subsidies to survive; yet they fail to realize that this eliminates the motivation for technological progress and development. Over the years, few studies have been conducted specifically on the economic viability of investing in straw biogas. Based on the subsidy standards set by the central government in 2015–2016, a subsidy of 1,500 yuan per m3 is provided for large-scale biogas projects; meanwhile, a subsidy of 4.11 yuan is given for each m3 of biogas produced annually. According to these standards, the fixed asset investment required to produce 1 m3 of biogas per year is 11.74 yuan ； A subsidy of 2,500 yuan per m3 is provided for pilot projects related to bionatural gas production; an additional subsidy of 6.85 yuan is given for each m3 of bionatural gas produced annually. Based on these requirements, the fixed asset investment required to produce 1 m3 of bionatural gas per year is 17.12 yuan. It is highly doubtful how much economic benefit such projects, sustained in this manner, can generate. 　　2. The gas production efficiency of straw biogas projects is low. Currently, the gas yield in many straw biogas projects in China is quite low. In some straw biogas projects that require investments of tens of millions or even hundreds of millions of yuan, the gas yield from air-dried corn straw amounts to only about 300 m³ per ton. There is still a considerable gap before corn straw can reach its maximum potential for biogas production, and this is mainly due to unreasonable processing methods. Methanogens grow and reproduce slowly, while humans are impatient; they always want to force straw to fit into various types of anaerobic digesters according to their own ideas, which has led to a wide variety of construction methods. Everyone hopes that straw can be processed quickly and efficiently to produce more gas, but in reality, the effort required is twice as much with half the result. In my opinion, whether it is a plug-flow, push-flow, or fully mixed type of system, and regardless of who is responsible for its design and construction, if its efficiency in producing biogas is low, then it is outdated; it lacks viability and is not worth promoting. There is only one standard for measuring the advancement or backwardness of various modes, and that is the level of gas production rate. What is the essence of the low gas production efficiency in straw biogas projects? Ultimately, it’s a problem of immature and substandard manufacturing technology. 　　3. The development of the straw biogas industry is slow. We can observe such a phenomenon: first, there are many units involved in the research design, with many well-known domestic colleges and universities as well as research institutions taking part ； Second, there are many companies that sell biogas equipment, materials, and instruments ； Third, there are many enterprises engaged in biogas project construction ； Fourth, there are many projects constructed with the help of **subsidies** ； Fifth, there are many cases where the structures are completed but do not function properly ； Sixth, there are few enterprises that rely on their own funds for construction and on biogas revenues for operation. This is something worth our serious reflection. 　　IV. Innovative Practices in Straw Biogas In July 2013, Yao Xuhua began new explorations and practices. He first had to deny himself, abandon the \"Qingxian Model\" he had adhered to for years, and turn to underground and semi-underground anaerobic digesters. Three years have passed in the midst of all this effort. But heaven rewards those who persevere; although we often faced financial difficulties, the results were still fruitful. 　　1. A new model for the development of straw biogas has been created. Pure straw, fully underground or semi-underground, with integrated gas production and storage. This model is beneficial both for heat storage and insulation, as well as for saving land and reducing investment. Straw does not require complex pretreatment, no adjustment of the carbon-nitrogen ratio is needed, and mechanical mixers are not required. 　　2. A new process for anaerobic digestion of straw has been innovated. In line with the natural laws of slow anaerobic digestion of straw and slow reproduction of methanogenic bacteria, long hydraulic, solid, and microbial retention times were achieved, resulting in the highest level in China for biogas production from straw – over 0.5 m3 of biogas per kilogram of air-dried straw (with 12% moisture content). 　　3. The anaerobic digestion of straw is exothermic. This discovery was first proposed by Yao Xuhua nationwide in 2013. Making full use of the heat generated during the anaerobic digestion of straw is of great significance for reducing energy consumption and enhancing the efficiency of anaerobic digestion reactions. This deserves great attention! We note that experts from the Biogas Science Institute of the Ministry of Agriculture, as well as scholars such as Shi Guozhong, Mei Zili, and Long Enshen from Sichuan University, also discovered this phenomenon during the experiments. 　　4. It overcame challenges such as the feeding and discharging of straw for biogas production, as well as the formation of a crust on the surface of the straw. In line with the formation of the shell, and by utilizing its characteristics and functions, new processes and equipment for feeding and slag removal have been designed. 　　5. Create multiple practical projects to meet market needs. For example, straw biogas is used in places such as Qingxian Shengfa Food Factory, the heating system for residential buildings in Tianjin Shuangtang, the production of plows for farming in Dingzhou, Hebei, and for heating food in villages in Yuzhou, Henan. These applications represent valuable explorations aimed at promoting the large-scale use of straw biogas in both civilian and industrial contexts. It has been reported multiple times by media outlets such as CCTV, People’s Daily Online, Xinhua Net, and People’s Daily’s \"Minsheng Weekly\". More details can be found online under “Yao Xuhua Biogas”. 　　V. Vigorously promote the industrialization of straw biogas 1. Revisit Deng Xiaoping’s and **’s instructions on biogas In July 1980, while inspecting rural biogas projects in Sichuan, Deng Xiaoping said: “Developing biogas is a good idea; it represents a viable approach to addressing rural energy needs based on local conditions.” The development of biogas requires a plan, with clear goals and directions for effort. To focus on research, biogas development also needs to pursue three aspects: standardization, serialization, and generalization. Without this, it is difficult to manage the process effectively, nor can quality be ensured. “This is a very good thing; everyone should pay attention to it.” 　　****It has been pointed out that: accelerating the development of rural biogas projects not only meets the requirements of developing a green energy economy and building a resource-conserving society, but also plays a significant role in promoting the construction of new socialist rural areas. At present, it is necessary to actively take effective measures to address the difficulties and problems at hand, and continuously improve the development level of rural biogas undertakings.” 　　Revisiting Deng Xiaoping’s instructions not only reminds us of Comrade Xiaoping’s meaningful question back then about whether biogas could be used to cook kidney meat, but also makes us aware of the profound significance behind his call for the \"three modernizations\" in the use of biogas. Now, standardization and serialization are more or less in place, but universality remains a major issue! How can it be industrialized and commercialized if it cannot be generalized? 　　To learn from and implement the instructions of ****, we must be bold in innovation, closely relate theory to practice, take active and effective measures, and strive to resolve the difficulties and problems at hand. We must also develop straw biogas technology with Chinese characteristics. Specifically: First, we must take active and effective measures to improve the economic viability of investments in straw biogas production, thereby reducing the associated costs. This is also an inherent part of supply-side reform! In my opinion, the fixed-asset investment required to produce each cubic meter of straw biogas per year must be reduced to less than 4 yuan. 　　Secondly, efforts should be made to address the difficulties and problems associated with straw biogas production, striving to improve its efficiency. By utilizing the most advanced anaerobic digestion technologies, it is possible to produce more than 0.5 m3 of biogas per kilogram of pure dry straw. 　　Third, reduce or minimize unnecessary consumption, and increase the energy output from straw biogas, so that the energy output from straw biogas reaches over 90%, while the energy consumed in the process remains below 10%. 　　Fourth, efforts are made to maintain simplicity and convenience; straw biogas projects with an annual production of less than 2 million m3 can be maintained by 2 or 3 people ； A straw biogas project with an annual production capacity of 10 million m3 is maintained by 7 to 8 people. 　　Fifthly, more attention must be paid to the economic benefits of straw biogas; by reducing investment costs and increasing gas production rates, large-scale straw biogas projects can recoup all their investments within 7 to 8 years. 　　Sixthly, it is replicable and can be widely promoted, thereby truly realizing the \"three modernizations\" envisioned by Deng Xiaoping, especially standardization, and thus advancing the development of rural biogas projects as proposed. 　　2. Accelerate transformation and upgrading to promote the rapid development of the straw biogas industry. Last year, **the relevant departments put forward the \"Work Plan for the Transformation and Upgrading of Rural Biogas Projects in 2015\"; I believe this plan is highly necessary and timely. Here are a few personal thoughts and suggestions: First, it is necessary to undergo a shift in mindset, moving away from a development approach that has long been guided by planned economy principles ； 　　Second, actions and measures must be upgraded to meet the demands of market economy development. 　　Thirdly, it is necessary to make policy concessions. The experience of over 30 years of reform and opening up tells us that whether it is Shenzhen’s approach to opening up to the outside world or the rural reforms in Xiaogang Village, a fundamental lesson is that at critical moments of major reforms, policies must allow for concessions and enable breaks from various constraints. 　　Fourth, **subsidies for the construction costs of biogas projects should no longer be provided, as this will prevent the development of the biogas industry. 　　Fifth, it is recommended to implement incentives for end products; a policy of 30 or 50 cents could be considered. That is, a reward of 0.3 yuan per cubic meter of biogas, and 0.5 yuan per cubic meter of biomethane. 　　The significance of developing straw biogas is extremely great. It is estimated that a super-large biogas plant with a daily production capacity of 11,000 m3 can generate 4 million m3 of biogas per year. This amount can replace 2,856 tons of standard coal as an energy source, which is equivalent to 2.4 million m3 of natural gas or 2,000 tons of crude oil. Additionally, it helps to reduce carbon dioxide emissions by 1,720 tons. Accelerating the development of modular systems will surely change the historical role of this clean energy source, turning it into a \"new energy industry based in rural areas\" and making a significant contribution to resolving China’s issues related to agriculture, rural areas, and farmers. 　　Article author: Zhang Hongyu