How to effectively improve
the level of resource utilization of agricultural waste in China
Agricultural wastes include plant wastes (residues produced during agricultural and forestry production), animal wastes (residues produced during animal husbandry and fishery production), and processing wastes (results from agricultural, forestry, animal husbandry and fishery processing Residues) and domestic garbage in rural towns. Agricultural waste usually refers to crop straw and livestock and poultry manure. China's agricultural waste presents four major characteristics, namely large quantities, poor quality, low prices, and harmful pollution. Hundreds of millions of wastes are generated each year, and pollution incidents are increasing year by year. Due to the low content of beneficial components in agricultural waste, that is, the available items are not high, and the content of harmful components is high, it must be in use. Received date: 2006-01. Detoxification is required, so costs increase. Although agricultural waste resources and rural biomass energy have been used for many years, some results have been achieved. However, at present, the utilization rate of agricultural waste in China not only has not improved compared with previous years, but has decreased. On the contrary, the pollution of livestock and poultry waste caused by straw incineration and intensive cultivation has become increasingly serious, and most farmers do not regard it as A kind of resource utilization, which is discarded or discharged into the environment at will, causing the original "resources" to become "sources of pollution", which has a great impact on the ecological environment. With the goal of quadrupling the GDP in China in the next 20 years and fully realizing the goal of a well-off society, how to deal with and multiply it by the author's brief introduction: Sun Zhenjun (1956-1), male, professor, doctoral supervisor; research direction: agricultural waste biological Transformation and comprehensive utilization, ecological engineering of agriculture and animal husbandry. Fund Project: Research project of the National "Tenth Five-Year Plan" for scientific and technological research (2004BA516A03); research project of the National 863 Plan (2001AA46092). Wanfang Data Phase 1 Status and Development of Agricultural Waste Recycling and Rural Biomass Energy Utilization in China 7 Organic waste is a realistic problem currently facing the “agriculture, rural areas and farmers”. Analysis of the current status and development trends of agricultural waste, find out the main limiting factors and technical bottlenecks that affect China's agricultural waste resource utilization, and propose development strategies and key technology areas for agricultural waste resource utilization and rural biomass energy in the next 20 years. It is of practical and far-reaching significance to turn agricultural waste into "waste" into "treasure", eliminate environmental pollution, improve rural ecological environment, and promote sustainable agricultural development. Too few separate storages reduce the quality of the soil, which results in increasing crop yields by applying large amounts of chemical fertilizers. The higher the amount of chemical fertilizers, the lower the utilization rate. Fertilization of agricultural waste can be realized, and the production of organic fertilizer can supplement soil nutrients and improve the effectiveness of trace elements in the soil. Increasing the application rate of organic fertilizers can reduce or slow down the use of chemical fertilizers on the one hand, and increase and maintain soil fertility on the other, and promote the sustainable development of agriculture. 1.3 Solving Rural Energy Shortages and Protecting the Ecological Environment The rural population in China accounts for more than 70% of the country's total population. Biomass has always been one of the main energy sources in rural areas, and 57% of rural living energy still relies on fuelwood and straw. The fuelwood consumption exceeds 15% of the reasonable harvesting volume, leading to the destruction of large-scale forest vegetation, intensified soil and water loss and ecological balance damage. Most of the biomass energy use in rural areas is based on direct combustion, which not only has low thermal efficiency (less than 10%), but also a large amount of smoke and dust emissions makes people's living and living environment worsening and damages the health of farmers. The use of biomass energy conversion technology can increase thermal efficiency by 35% to 40%, save resources, improve the living environment of farmers, and improve living standards. Practices in the construction of ecological agriculture and ecological homes throughout the country since the Ninth Five-Year Plan period have proven that the effective use of agricultural and forestry wastes and town and village domestic wastes, and the development of rural biogas and other energy engineering and ecological agricultural models can effectively promote a virtuous ecological cycle and reduce The destruction of forest resources reduces soil erosion and soil erosion and protects biodiversity. 1.4 Biomass energy contributes to national energy and power shortages China has changed from an oil exporter to an oil importer. In 2000, the net import volume has reached 70 million tons. Biomass can be converted into liquid fuel through various processes, which can directly replace petroleum fuels such as gasoline and diesel as civilian fuel or internal combustion engine fuel. In the same period, the amount of biomass resources including agricultural waste in China reached 700 million tons of standard coal. In 2020, the amount of biomass resources will reach at least 1.5 billion tons of standard coal. If 50% of it is used to produce liquid fuel, it will provide 200 million tons of liquid fuel for China's oil market. In addition, if we can adopt measures such as planting energy plants (energy crops and energy forests) to develop China's biomass resources, it can promote the adjustment of agricultural structure, increase rural employment opportunities and rural residents' income, and have important significance for revitalizing the rural economy. Biomass energy from agricultural and forestry waste can contribute to filling the rural electricity supply gap. In 1999, China ’s total power production was 1.260 trillion kWh, and the per capita electricity consumption was less than 1,000. 1 The significance of resource utilization of agricultural waste in China 1.1 Elimination of increasingly serious environmental pollution At present, China is the world ’s agricultural The country with the largest waste output has about 4 billion tons per year, of which 2.61 billion tons of livestock and poultry manure emissions, 70 million tons of crop straws, 25,000 tons of plastics such as waste agricultural membranes, and vegetable waste. 100 million to 150 million tons, 250 million tons of household waste and human waste in towns, and 50 million to 65 million tons of waste from meat processing plants (including meat mills, leather mills and slaughterhouses) 25 million tons of cakes, and forestry waste (excluding charcoal forests), amount to about 37 million m3 per year, which is equivalent to 10 million tons of standard coal. In the past, Chinese farmers used agricultural waste as organic fertilizer, which played a huge role in promoting the material energy cycle and fertility improvement. However, with the development of the market economy, the conversion of agricultural waste into organic fertilizer is facing a series of new problems and severe challenges. On the one hand, the composition of waste has changed a lot. At the same time, the planting industry has gradually shifted to labor-saving, labor-saving, efficient, and clean cultivation methods. Traditional organic fertilizer accumulation, production, storage, and use technologies have been unable to adapt to the development of modern agriculture. Therefore, agricultural waste is no longer welcome and becomes a source of pollution that seriously pollutes the ecological environment. The main manifestations are: ① odor, straw burning, and greenhouse gas emissions, which have aggravated air pollution; ② heavy metals, pesticides, and veterinary drug residues contaminated soil, increasing the resistance of environmental organisms; ③ agricultural "white pollution" seriously affects soil normal functions; ④ Cross-flow of sewage increases non-point source pollution and eutrophication of water bodies; ⑤ Virus transmission, disease spread, especially zoonotic diseases. 1.2 Maintaining and improving the quality of arable land soil China feeds 22% of the world's population with 10% of the world's arable land area and maintains its fertility, in a sense due to the application of organic fertilizer. However, with the increasing intensification of agricultural production and the increase in the input of means of production, agricultural production has developed by leaps and bounds, and traditional organic fertilizers are being abandoned. At the same time, according to the National Fertilizer Experiment Network's long-term positioning experiments on fertilizers and national soil fertility and fertilizer benefit monitoring data, in recent years, the organic matter content of cultivated soils has decreased, soil buffer capacity has weakened, and disaster resistance has declined; fertilizer utilization has been low; soil fertility has decreased. KWh / person / a for soil cultivation is only about 1/5 of that in South Korea, while per capita domestic electricity consumption is even lower, only about 110 kWh / person / a. In particular, the rural power supply gap is larger. In order to achieve the goal of doubling the national economy in 2020, ensuring power supply is a necessary condition. Utilize local biomass energy resources, such as straw, fuelwood, chaff and wood chips, according to local conditions, to build data. 8 China Agricultural Science and Technology Review 8 Volumes Stand-alone, decentralized or independent off-grid or grid-connected power plants have broad market prospects. If 50% of the current agricultural and forestry waste production is used as fuel for power stations, it can generate 400 billion kWh, accounting for about 30% of China's current total power consumption. Put an end to it, with the development of agriculture, its total can only increase. Before the 1980s, the amount of agricultural waste in China was small and scattered, and there was almost no problem of agricultural pollution by the environment. Today's agricultural waste pollution is mainly the result of intensive agriculture, which has concentrated waste in a large amount and exceeded its environmental capacity. According to the “end-of-governance” method of the environmental protection department, the treatment effect is not good. To meet the emission standards, the treatment costs are high, the agricultural costs are increased, and it is not conducive to agricultural development. The scale of farm construction in foreign countries has been developed to small and medium-sized, and must be matched with certain consumption land or processing facilities to be approved. Source control is to control the scale of breeding. The whole process includes pre-natal feed, aquaculture techniques and methods during production, and post-natal fecal disposal and treatment. Improve feed utilization, reform aquaculture processes, reduce nitrogen and phosphorus content in solid waste, and reduce wastewater generation, chemical oxygen demand (COD), and biochemical oxygen demand (BOD) emissions. It will not only be beneficial to the development of the breeding industry, but also eliminate the environmental pollution caused by manure. 2 Current status and development trends at home and abroad 2.1 The concept of circular economy is spawning “waste” as a new industry Waste is generated in the primary, secondary, and tertiary industries, but does not depend on any industry. The optimal allocation of resources and the recycling of waste are the core of the circular economy technology system. The waste needs to rise to an industrial status to adapt to it. This report clearly proposes the concept of waste as a “fourth industry”. As an important component of the rural circular economy, the recycling of agricultural waste will become the basis for the sustainable development of agriculture and rural areas and even an important link in the construction of a well-off society in rural areas. The recycling of agricultural waste has been promoted from a pollution control and environmental protection technology and strategy to the height of circular agriculture and circular economy. This is directly related to the sustainable development of agriculture and the construction of a well-off society in rural areas. Waste recycling, recycling, agriculture, and recycling economy are the development direction and goal of the waste industry. 2.2 The combination of agriculture and animal husbandry and ecological cycle is the simplest and most effective way. The planting systems in European and American countries are mostly one season a year. At harvest, a straw grinder is hung behind the combine or a deep plow is directly hung into the soil. Within, directly returned to the field. The United States began to study the technology of no-tillage mulch in the 1940s, and 70% of the arable land is now under no-till mulch cultivation of crop straw. Some farms ferment straw silage and use it as feed to return to the field. Utilization of crop straw is better in Western European countries, with about 20% of the straw being used as feed. According to statistics from the Food and Agriculture Organization of the United Nations, about 73% of meat in the United States is converted from grass, about 90% in Australia and 100% in New Zealand. It can be seen that the “straw-animal husbandry” agricultural-pastoral combination is the simplest and most effective way to use crop straw resources. From the perspective of the development of the breeding industry, the livestock and poultry breeding in developed countries is mostly carried out by individual farms, with small and medium scales as the mainstay. Waste treatment methods are mainly dry manure removal and water flushing, and the utilization methods are mainly used for composting and anaerobic fermentation and harmless treatment, and then directly used in farmland and grassland. 2.5 Food safety brings new opportunities and challenges to agricultural waste recycling. Food safety has become a worldwide issue that is closely related to human survival, economic development and social stability. In addition to pesticide residues and animal antibiotic residues, in recent years, Europe has been plagued by mad cow disease, foot-and-mouth disease, swine fever and dioxin, and Asia by severe animal diseases such as bird flu and food safety. The food safety crisis has finally turned pollution-free agriculture and green food production into the mainstream of agricultural and pastoral production. The production of clean animals and plants has improved the “cleanliness” of agricultural waste, and the toxic and hazardous substances contained in it have been significantly reduced, creating conditions for the further development of agricultural waste. At the same time, the practice of ecological agriculture has pointed out the way to turn "waste" into "treasure". The pollution caused by agricultural waste is mainly on the ecological chain composed of "producer-consumer-decomposer". The decomposition link forms a bottleneck and cannot form a benign Material circulation and energy flow, excessive accumulation causes pollution. According to the principles of ecology and ecological engineering, the ecological agriculture developed in China in the early 1940s has adopted the agricultural waste resource recycling technology as an interface technology to construct the "four pigs, one marsh and one fruit", Many eco-agricultural engineering models including the “Integration” have promoted the improvement of regional environmental quality and economic development. Practice has proved that the resource-based technology of agricultural waste can only do more with less when combined with the ecological agricultural model. One of the development trends of agricultural waste resource utilization is to upgrade or research and develop new agricultural waste ecological technologies. According to the principles of ecological cycle and circular economy, it will be optimized and assembled with other technologies into new ecological agricultural engineering and regional development models. Establish corresponding demonstration bases according to different regions and ecological types, while ensuring the sustainable use of resources, maintaining ecological balance, and improving environmental quality, comprehensively promote rural economic and social development. 2.3 From the "end treatment" to the source control, the whole treatment direction is developed. Agricultural wastes, especially wastes from aquaculture, are biological metabolism. The product is different from industrial waste and is a natural product. There is no data available. Phase 1 The status and development of China ’s agricultural waste resource utilization and rural biomass energy use. 9 Agricultural chemicals in green and organic food production ( The restriction or prohibition of chemical fertilizers) provides opportunities for the opening of the market for commercial organic fertilizers that use agricultural waste as raw materials; but at the same time, higher technical requirements and quality standards have been proposed for the treatment and recycling of agricultural waste. 2.6 Development of waste resource-based products towards diversification, materialization and high-value development China's agricultural organic waste production is large, scattered in the vast countryside, difficult to store and transport, and the level of processing and utilization technology is low. Mainly for agricultural use. It is estimated that fertilizer, feed and fuelization of agricultural waste will remain the main development direction in the past 5-10 years. However, new technologies and business concepts must be used to overcome the problems of low utilization value, poor quality of fertilizers and feeds, and low commodity value. The problem of comprehensive utilization of agricultural wastes is a major issue that needs to be solved in many countries around the world. Especially with the increasing shortage of natural resources and the rapid increase in the amount of waste, agricultural waste is getting more and more attention. In today's market economy and industrialized operation, the "oldest three" (returning fields, silage, compost) have been Not adapted to the needs of development. With the goal of high-value product development, comprehensive utilization of agricultural waste resources is one of its development trends. The use of agricultural waste to develop new types of biomaterials, biochemical products, and alternative petrochemical products and scarce resource substitutes has received increasing attention, which has greatly expanded the field of agricultural waste resource utilization.