Introduction: Municipal solid waste management is a social hot issue that people are generally concerned about at present. At the two sessions of the National People's Congress, the Central Committee of the Democratic National Construction Association proposed to strengthen the construction of domestic waste management system, clearly deal with alternative technologies, speed up the pilot work, strengthen publicity and education, and raise residents' environmental awareness. Management mode of municipal solid waste
1 Analysis of main problems
In 23, the domestic solid waste removal capacity of 66 cities in China reached 15 million tons, increasing at an annual rate of about 4%. According to statistics reported by various places, the harmless treatment rate of municipal solid waste is about 51%. However, according to the investigation and analysis of 388 domestic waste treatment plants (factories) in 255 cities, the compliance rate of harmless treatment facilities of domestic waste in China is about 25%, and the actual harmless treatment rate is less than 2% considering factors such as operation management. The problem that garbage pollutes the environment and harms people (especially farmers) is very prominent.
in recent years, the state has implemented a proactive fiscal policy, and urban garbage disposal has been supported, and a number of national debt projects have been built. At the same time, by promoting market-oriented reform, the diversified pattern of investment subjects began to take shape, and the treatment of municipal solid waste began to enter a period of rapid development. However, generally speaking, the development direction of municipal solid waste treatment is not clear, the technical route that really suits the national conditions has not yet been formed, and some tendentious problems have emerged, which may affect the healthy development of the whole industry.
1.1 The proportion of landfill treatment is too large
It is difficult to meet the requirements of sustainable development and circular economy. At present, the proportion of landfill disposal exceeds 85%, and the problem is also the most prominent. First, it consumes a lot of land resources, and it is difficult for many cities to find new landfills; Second, a large amount of leachate is produced, and most garbage dumps have leachate pollution problems; Third, landfill gas pollutes the atmosphere and has potential safety hazards. At present, less than 3% of landfills can recycle landfill gas. Fourth, most recyclable resources cannot be recycled once they are buried. The investigation also shows that the investment in building a standardized and harmless landfill is not as economical as expected. A landfill with a daily garbage disposal capacity of 1 t (service life of 2 years, serving about 1 million people) needs an investment of 2-3 million yuan, and the garbage disposal cost per ton (including investment cost) reaches 6-8 yuan.
1.2 Incineration treatment is developing rapidly
There are hidden dangers and risks in some projects. Waste incineration for power generation is one of the main ways adopted by European and American countries and Japan. In recent years, China's waste incineration technology has developed rapidly. At present, about 5 domestic waste incineration plants have been put into operation, and nearly 1 waste incineration projects are under planning and construction. Dongguan alone plans to build more than 1 waste incineration plants. Waste incineration power generation has certain advantages in waste reduction and heat energy utilization, but some tendentious problems must be calmly analyzed in the development process. First, the investment and operating costs are high. The daily investment of 1 t garbage disposal project is 4-6 million yuan, and the average cost of garbage disposal per ton exceeds 1SO yuan; The second is to rely on higher on-grid tariffs. The on-grid electricity price of coal-fired thermal power generation is about .3 yuan per kWh, while the on-grid electricity price of garbage power generation generally exceeds that of .5 yuan. In order to chase the power generation income, some enterprises add too much coal, which actually evolved into? Small thermal power? Project; Third, the fly ash produced by incineration has not been properly disposed of. According to the requirements of environmental protection, fly ash should be treated as hazardous waste because it contains excessive toxic and harmful substances, and the disposal cost is as high as 1 yuan /t, that is, the disposal cost per ton of garbage will increase by tens to hundreds of yuan. This cost is largely ignored. In addition, the dioxin pollution caused by garbage incineration is still the focus of attention from all walks of life. The calorific value of domestic waste in China is low, about 1/3 of that in developed countries, and it is not suitable for incineration. Burning garbage with coal is a helpless move, and the heat utilization efficiency of coal is about 1/2 of that of conventional boiler. Whether it is reasonable in terms of technology and economy needs further study.
1.3 bio-composting technology is mixed
A number of national debt projects have been completed? Garbage project? . Composting domestic waste has been used for a long time in China, but the effect is not good. The outstanding problems are low garbage sorting efficiency, poor fertilizer quality and no market. Recently, a batch of garbage disposal projects in Sichuan and Anhui were investigated, and most of them used mechanical sorting and biological composting technology, which could not operate normally. The main reasons are: first, some departments make mistakes in decision-making and lack supervision; Second, the design idea is wrong, the technology is immature, the equipment is shoddy or blindly introduced.
2 Adjustment of thinking
2.1 Re-understanding of the characteristics of domestic waste
The main characteristics of domestic waste in China are different from those in developed countries. First, the water content of domestic waste in China is high, generally 55%-65%, and it is as high as 7% in some southern cities in summer, while it is generally 3% in western countries? 35%。 Second, the proportion of organic wastes such as kitchen waste and catering in China's domestic waste is large, accounting for 45%? 55%, generally around 2% in western developed countries. Third, the domestic waste in China is still mainly mixed collection. Although the classified collection of domestic waste has been vigorously promoted in recent years, it has achieved little effect. Most cities in China deal with mixed primary garbage. However, the classified collection rate of domestic waste in developed countries is over 6%, and that in some European countries such as Germany is over 8%.
these characteristics of domestic waste in China make the problems we face more difficult than those in developed countries. First, the leachate produced by landfill is large and the concentration of pollutants is high; Second, the calorific value of domestic garbage is low, and most of it is not suitable for direct incineration; Third, does the mixed garbage have? Sticky? It is difficult to mechanically sort, the resource recovery rate is low and the compost quality is poor. Over the years, we have attached great importance to learning from or introducing foreign technology and equipment, but practice shows that foreign technology and equipment are not fully applicable in China. It is imperative to further understand the characteristics and impact of domestic waste in China, strengthen targeted research and practice, and develop technologies and equipment suitable for the national conditions.
2.2 Reflection on the technical route
Over the years, our technical research and capital investment have focused on two aspects. First, on the basis of introducing foreign technology and equipment, we have carried out necessary transformation and localization to make it suitable for garbage disposal in China; The second is to strengthen the treatment of terminal pollution to meet the requirements of environmental standards.
In the landfill treatment, in order to prevent the leachate from polluting the groundwater, we have adopted internationally popular artificial seepage control measures, such as the anti-seepage structure of geotextile with high density membrane in poor areas in the Three Gorges reservoir area. In order to purify leachate, some areas have introduced expensive? Reverse osmosis? Technical equipment, the investment per ton of sewage treatment is nearly 1, yuan, and the operating cost is tens of yuan. In the aspect of incineration, we have studied the adaptability of low calorific value garbage for many years, but it is impossible to change some basic laws of combustion science, and low efficiency and high cost of combustion are inevitable; Due to the complex composition of mixed domestic waste and serious incineration pollution, international advanced treatment technology has been adopted at present, and the investment in flue gas treatment is almost equal to that of incineration main body. In terms of bio-composting, some cities have introduced machinery and equipment from the United States and Germany, but they still can't solve the sorting problem of domestic waste.
It is correct in principle to learn from foreign experience and strengthen pollution control, but in the face of practical problems, we should reflect: First, should foreign technology adapt to China's garbage, or should China's garbage adapt to these technologies? Second, blindly emphasize the end treatment of pollution, or control and reduce pollution from the source? On the basis of investigation, scientific experiment and engineering practice, we put forward some suggestions for adjusting the technical route:
First, most municipal solid waste is suitable for biological pretreatment, with emphasis on reducing the moisture and organic matter in the waste, improving the characteristics of the waste, and creating conditions for subsequent treatment and reducing pollutants; Second, strengthen the mechanical separation of garbage, improve? Sorting and sorting efficiency of Kunming garbage; Third, rational selection of classified disposal technology, complementary advantages; Fourth, prudently develop the incineration technology of mixed waste and strengthen the comprehensive evaluation of technology and economy; Fifth, limit the direct landfill of mixed garbage, control pollution at the source and reduce land consumption.
2.3 About resource recycling
It is generally believed that China's huge? Army of scavengers? The problem of resource recovery in garbage is basically solved. In the final treatment process, there are few wastes that can be directly recovered, and the resources are mainly used by incineration for power generation. However, the survey shows that in the final treatment of domestic waste, more than 2% of the waste can be directly recovered, including 6%-9% of plastic and rubber, 4%-6% of paper, and a certain amount of fabric, metal and glass. Once these recyclable materials are burned, they not only have low utilization efficiency, but also cause serious smoke pollution. Practice has proved that as long as the mechanical sorting and screening technology is solved, most of the available resources in the garbage can be directly recovered, and at the same time, high-quality base fertilizer accounting for about 8% of the total garbage can be produced, which can be first used for urban greening and forestry. China is a country lacking in resources, so we should vigorously develop circular economy, pay attention to the direct recycling of garbage resources, and strive to develop domestic garbage treatment into a resource recycling industry.
3 Enlightenment from demonstration projects
Since 1996, American Business International Group (hereinafter referred to as? American business? ) More than 2 cities in China were investigated and the characteristics of domestic waste were deeply studied. In 1998? American business? The first comprehensive waste treatment plant was built in Daqing City, which also experienced a series of setbacks (the equipment imported from the United States became a pile of scrap iron), but it began to explore the treatment ideas and processes suitable for the characteristics of domestic waste in China. In 22, Pudong New Area in Shanghai, after many investigations and strict argumentation, was determined by? American business? Invest in the construction of a comprehensive garbage treatment plant to treat 1 t tons of domestic garbage every day. In May 23, the project was completed and put into trial operation. The new ideas and market-oriented operation mode of the project have aroused great concern of the Ministry of Construction, and sent people to conduct research for 8 times, and organized experts to follow up the investigation. In February, 24, the Urban Construction Department of the Ministry of Construction held a site meeting for further investigation and discussion. According to expert evaluation, the project adopts a comprehensive treatment technical route according to the characteristics of garbage in China, which fully reflects? Reduce, recycle and be harmless? The principle provides practical experience for large-scale projects and has important reference significance. In April, 24, the project was included in the science and technology demonstration project of the Ministry of Construction.
The main features and benefits of this project can be summarized as follows:
3.1 Efficient biological pretreatment technology
Through aerobic fermentation in silo, the reduction of moisture and organic matter in garbage is realized at first. The water content is reduced from 6%-8% to about 35%, the volatile organic compounds are degraded by about 5%, and the total mass is reduced by about 4%. The characteristics of garbage are improved, which is beneficial to mechanical separation and subsequent treatment.
3.2 Advanced mechanical sorting equipment
A complete set of domestic equipment has a recovery rate of over 9% for available resources in garbage, including plastics, paper, metals, glass, batteries and lighters. At the same time, realize the automatic classification of garbage.
3.3 Applicable classified disposal technology
Secondary fermentation of organic matter and refined composting produce about 8% of the total garbage; Burning of bamboo, wood, paper and textiles, and utilization of heat energy; Landfill the residue, and minimize it (no more than 2% of the total garbage).
3.4 reasonable? Three wastes? Treatment method < P > The moisture of garbage is mainly removed by water vapor evaporation, and a small amount of leachate is reused for secondary composting fermentation; Organic matter turns harm into benefit through biochemical composting; Burn with? Firewood? Mainly, smoke pollution is reduced; Residue landfill should be minimized, inorganic and low in moisture, so as to reduce pollutants from the source; Adopt biological deodorization technology to effectively control air pollution.
as a market-oriented operation project, American business? The construction investment is nearly 2 million yuan, and it bears all the operation responsibilities and expenses. According to the franchise agreement, Shanghai Pudong Environmental Sanitation Management Department sent supervisors to supervise the whole process, and the government paid the garbage disposal fee per ton of 5 yuan. This cost is equivalent to 1/4 of incineration treatment, even lower than the cost of landfill treatment. Of course, investors also have their own profit model. It is understood that by selling? Scrap? Every ton of garbage can earn more than 3 yuan, and every ton of organic base fertilizer can be sold around 2 yuan.
? American business? The demonstration project has given us important enlightenment: First? Reduce, recycle and be harmless? The garbage disposal mode can be realized; Second, a win-win market mechanism between the government and enterprises can be established.
4 Suggested measures
4.1 Strengthen scientific research on waste pretreatment technology
Through biological pretreatment, water and organic matter can be reduced and the characteristics of domestic waste can be improved, which may have a positive impact on subsequent incineration and landfill. According to our preliminary test of Beijing Shunyi Waste Incineration Plant, after simple biological fermentation and screening, the amount of domestic waste is reduced by nearly 5%, and the calorific value is increased by about 2.5 times, which has remarkable technical and economic benefits.
4.2 Strengthen the development of garbage sorting equipment
? American business? Experience has proved that biological pretreatment will create favorable conditions for mechanical separation, and it is also crucial to improve the performance of separation equipment. It is suggested that the state arrange appropriate support funds to support the research and development of domestic sorting equipment and further improve the efficiency of resource recovery. At the same time, we should strengthen the right? Scrap? The supervision and management of processing and utilization will be gradually solved through the development of standardized and large-scale resource recycling industries? Army of scavengers? The problem.
4.3 Encourage the use of recycled organic fertilizer
The city government should formulate policies to encourage the priority use of garbage compost in urban greening and forestry, and gradually reduce the use of chemical fertilizers.
4.4 On the basis of practical verification, adjust and improve the technical policy
Advocate biological pretreatment of domestic waste, with emphasis on reducing moisture and organic matter in the waste, so as to create conditions for subsequent treatment and pollution reduction; Strengthen the mechanical separation of garbage and improve the efficiency of mixed garbage sorting and classification; Reasonable selection of classified disposal technology, vigorously develop the recycling industry of garbage disposal resources, gradually limit the direct landfill of mixed garbage, pay attention to source control of pollution, and reduce the consumption of land resources. Management mode of municipal solid waste
The Central Committee of China Democratic National Construction Association proposed to strengthen system construction and formulate the Municipal Solid Waste Management Law.
cities should formulate supporting implementation rules according to the actual situation, so that all aspects of garbage disposal can be brought into the track of legal management. At the same time, explore and improve the price adjustment mechanism of garbage charges, adhere to the principle of producer paying, and promote the recycling and reduction of municipal solid waste through price leverage.
strengthen the government-led model and improve the efficiency of administrative management.
Strengthen supervision and remediation, clearly replace sanitary landfill treatment process with new technologies such as incineration and resource treatment, and formulate urban life as soon as possible.