Comprehensive treatment of plastic waste energy

Abstract: The paper analyzes the current situation of the production and disposal of plastic waste in the United States and China, and proposes that the comprehensive treatment of energy is a clear advantage and feasible solution.

Keywords: plastic waste; energyization; comprehensive treatment; analysis of economic benefits

There is a large amount of plastic waste in urban living garbage, which is irregular in shape, dirty and mixed and cannot be classified. The technology for recycling plastic waste of this type has not yet been produced internationally and can only be handled terminally in government landfill/incineration facilities. The plastic waste referred to in this article is such garbage.

First, the United States plastic waste disposal situation

In 1995, the total amount of plastic waste collected in the United States was 19 million tons, accounting for 9.1% of all garbage. The volume of landfilled and incinerated plastic is 18 million tons, accounting for 11.8% of all landfilled and incinerated garbage. Plastics are the third largest waste category in the United States after paper and yard waste. In 1995, the nation’s total garbage removal volume was 201 million tons, of which plastic waste was 19 million tons, accounting for 9.1%; in 1995, the total amount of urban waste disposal in the United States was 151.9 million tons, including 18 million tons of plastic waste. 11.8%.

Plastic waste has serious urban pollution, plastic waste is light, incompressible, easily inflated, airtight, exacerbating the breeding of anaerobic bacteria, leading to problems such as groundwater pollution, biogas explosion, and large-scale land occupation. The developed countries have generally banned the landfilling of plastic waste, and plastic waste cannot be landfilled and the charges for incineration wastes are rising. However, the problem of burning litter containing plastics is also seriously concerned. Due to the limitation and control of the quantity and type of incineration of plastic waste, the development of RDF and PEF technologies is closely related to the use of plastic waste with the highest heat value in waste.

The average heat value of plastic waste is the highest among all waste types, reaching 6,400 kcal/kg in the United States. It has the most energy and economic value in all municipal solid waste. Incineration power generation technology depends on plastic waste, in order to increase the calorific value, in exchange for electricity. According to statistics from the US Department of Energy, 20% of the calorific value of waste incineration comes from plastic when the waste contains 5% of plastic. However, the total energy efficiency of waste-to-energy projects that use waste energy to convert electricity into electricity is generally only 10% to 20%.

In the United States in 2000, between 7% and 10% of plastics were recycled into carpets, textiles, and park supplies through mechanical recycling. 90% of plastic waste can only be landfilled or incinerated. This is the lowest level of comprehensive treatment and recycling of municipal solid waste in the United States over the years. Trash variety. In 1996, the US Environmental Protection Agency announced the prediction of the level of recycling efficiency of various types of waste treatment technology, but it is still doing nothing about plastic waste.

Incineration technology requires plastic waste to supplement calorific value, while at the same time it needs to control the quantity and type of plastic. Therefore, in this sense, the development of RDF and RDP technologies are both energy-based technologies, and at the same time they are technologies that prevent pollution from incineration of plastic waste. Full-scale incineration technology (WTE) is being strictly controlled, and waste-to-energy generation is increasingly difficult to withstand huge losses and decline. The distribution of various types of waste treatment technologies released by the US Environmental Protection Agency from 1960 to 2000 shows that in the United States, where waste classification has been greatly developed, incineration technology has always been controlled by the U.S. government at about 15%, without significant development.

From this, it can be seen that what sort of technology is used for plastic waste in urban household garbage terminal treatment facilities is a difficult problem for the selection of terminal treatment technology for urban household garbage.

Second, the problem of plastic waste in China is getting worse

The issue of plastic waste in China has become the focus of attention of the government and the public. The rapid increase in plastic waste has caused the plastic content of large cities in China to reach the level of developed countries. China's total municipal solid waste transport volume is 140 million tons/year. The plastic content of the average domestic garbage in 668 cities is about 5% to 10%. The plastic content of some big cities is even more striking (see Table 1).

Waste energy is an important part of non-renewable energy. Plastic waste is the main type of waste energy. A ton of plastic takes about 3 tons of oil to synthesize. In the garbage that is landfilled and burned every year in the country, even if plastic accounts for 5%, it is as high as 7 million tons/year, equivalent to an annual consumption of 20 million tons of oil. Due to the high energy characteristics of plastic waste, according to China's urban landfill-based conditions, localized energy development technology specifically designed for plastic waste will be developed to improve the comprehensive treatment technology of municipal solid waste, and catch up with the international municipal solid waste treatment technology level. The market-oriented, product-based, and efficiency-oriented comprehensive waste disposal technology projects are imperative.

Third, comprehensive treatment of plastic waste energy

The technical solutions of the municipal solid waste comprehensive treatment project include landfill, incineration, power generation, fertilizer production, building materials, plastic granulation, and sorting. Together, these projects are intended to complement each other with technical defects and increase the use of recycled products. The significance of plastic waste can be influenced by the overall situation. It lies in its combination of energy, value, and environmental issues. Once its energy goals are realized, many urban waste disposal projects will receive new environmental protection, energy, and economic benefits. . Many project designs and program options will consider material balance on the basis of waste logistics, and then consider energy balance; re-consider costs and investment accounting; re-select technology platters; re-research market prices; re-measure land planning; rethink waste conservation Rules and so on. When it comes to seeing a lot of stench-plagued filthy plastic waste becoming a golden environmental fuel with high market value, government leaders, corporate managers, technical design departments, and investors in basic capital markets can't be irritated. .

Comparing the problems of the above-mentioned types of mainstream technologies, it is not difficult to see whether plastic waste can be processed on a large scale and become the main difficulty in realizing comprehensive treatment and recycling of urban household waste. Once this problem has been solved, the concept of integrated processing will be a major leap forward.

1. Waste volume reduction can improve the comprehensive recycling efficiency of existing waste disposal projects.

The major constituents of urban waste in China are humus, soil and plastic (wet-based) organic matter. They account for more than 60% of the municipal waste weight and 60% of the volume. The weight and volume of plastic waste is second only to humus. It is the second largest category of municipal solid waste, accounting for 20% of the municipal solid waste volume. The reduction of waste to landfills means that the life span of 1/5 to 1/3 can be correspondingly extended, which means that the corresponding landfill investment costs and running costs are saved. For fertilizer production, incineration, building materials and even plastic granulation projects, the significance of this reduction is equally obvious.

2. Garbage-free harmonization technology can improve the environmental protection level of existing waste disposal projects
Plastic waste is completely screened out into the energyization process in urban transit or landfill and fertilizer projects. It not only completely administers the environment, but also creates a benign waste condition for landfill waste. In cities without plastics, groundwater pollution and hidden dangers of biogas explosion may be cured. Similarly, a fertilizer-free project without plastics will greatly optimize the quality of the process product and the difficulty of the process. Even for burning, there is no burning of plastics, which will greatly improve the environmental conditions and reduce the possibility of dioxins and other pollution.

3. New energy resources bring new economic momentum to various waste treatment projects and local markets

Plastic waste is a valuable energy resource. An integrated waste management company often combines landfill, fertilizer, building materials, and incineration. The internal energy consumption of enterprises is huge and there are no energy bonds between them. Different technologies have different energy consumption. Boilers used in building materials, heat sources needed to make fertilizers, energy fuels to be burned, drying required for sorting, and domestic heating of landfill companies all require non-electrical energy fuel oil. When the plastic waste content meets the conditions, these fuel gas can be converted through the project's own plastic waste, making these projects become zero energy consumption projects. According to our demonstration plant's 10 tons/day practical experience, its power consumption is 65,000 kcal/hour, while fuel gas output is 1.79 million kcal/hour. Even considering the combustion efficiency factors, these thermal energy are sufficient to meet the energy needs of an integrated treatment project.

Waste energy comes from garbage. Garbage cannot be stored or transported in large scale. In most small and medium-sized cities, the scale of waste generation is relatively limited. Therefore, waste-to-energy generation is generally not desirable and feasible. If these small and medium-sized cities abandon the recycling of energy from plastic waste, not only will the country’s macro energy waste be serious, but also the local sources of additional energy resources will be lost. A medium-sized city with a daily capacity of 1,000 tons of rubbish, if the plastic content is 10%, the amount of plastic waste per day is 100 tons and 36,500 tons per year. According to the 70% energy conversion rate, the local government authorities should have 25,500 tons of energy fuel gas every year as a resource supply society, with a total of 400,000 tons within 15 years of landfill life. Compare the calorific value of coal by 5,000 kcal/kg, roughly equivalent to 50,000 tons of coal/year, or 750,000 tons/15 years. Taken together, the complementary, integrated and comprehensive optimization functions of the plastic waste energy technology for various existing municipal solid waste comprehensive treatment facilities are shown in the following diagram.

IV. Economic Benefit Analysis of Plastic Waste Treatment in China

The existing waste disposal projects in China must rely on government investment and subsidies (recycling fees) from investment to operation. The difficulty of the urban waste treatment industry's difficulty in attracting capital for capital operation is that there is no market-oriented product for waste disposal. Whether the government can guarantee subsidies and charges is also the key to whether the capital is willing to enter the urban waste disposal field. Large-scale incineration of power generation is not affordable for small and medium-sized cities and towns. After a large number of landfills in China have relied on the construction of national debt, they have ceased to be in business or have been out of business, and are unable to operate. Strengthening the education of waste sorting and strengthening the waste collection system will inject vitality into these enterprises, bringing impetus to the cause of environmental protection. However, waste collection and waste classification will be a long process of construction and cannot directly bring the current benefits of waste terminal processing companies. In terms of government investment, the investment funds of waste companies are tight because there is no fiscal expansion. The non-benefit projects that want to transition to attract capital markets and do not realize accelerated acceleration of garbage charges will also not receive substantial sources of capital.

The comprehensive treatment technology of plastic waste energyization provides an economic basis for realizing this kind of investment operation mode. While it brings benefits to enterprises, it is also improving the conditions for waste processing companies to bridge the capital market, and the two are mutually reinforcing. After a long period of operation of the plastic waste energy demonstration project demonstration plant, we compared the basic economic conditions of plastic waste and landfill projects. According to the current big city subsidy or fee standard, when the garbage charge or subsidy is RMB 50/ton, the landfill cost is about RMB 40 and the profit is about RMB 10/ton.