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Recycling: promote the harmonious development of plastic packaging materials and the environment (IV)

4 simple evaluation of plastic packaging waste treatment methods

4.1 landfill treatment

for MSW treatment, landfill treatment is a method with a long history, relatively simple technology, and relatively economic. However, this law occupies limited land resources on earth, and ordinary landfills have been strongly opposed by local government departments and local residents in recent years because of their simple facilities, the leachate of landfills will pollute groundwater sources, and the methane gas escaping will pollute the air and be prone to explosion; The modern sanitary landfill has increased the investment of the landfill due to the addition of anti-seepage liner, exudate drainage device, and methane emission device, and the landfill treatment cost has also increased sharply. Therefore, although the amount of MSW in the world has been increasing in recent years, the number of landfills has decreased sharply. This trend will continue in the future. In the past, most plastic waste was landfilled with MSW. However, due to its light weight, large volume and good stability, it has been buried underground for a long time and is not easy to decompose. In essence, it has become a waste buried underground for a long time, which does not solve the problem of polluting resources, but instead wastes a lot of valuable raw material resources and energy in plastic waste, Therefore, it is considered unwise to treat plastic waste by landfill, and it is increasingly restricted

4.2 incineration treatment

incineration treatment is an effective method for MSW treatment in European countries, with the main purpose of eliminating garbage at the beginning. Due to the high calorific value of plastics, and harmful gases will be generated when some plastics such as PVC are burned, which is easy to damage the furnace body and pollute the environment. In addition, the incinerator equipment investment is large and the treatment cost is high. It is reported that the incineration treatment cost of MSW per ton in Germany is 53 US dollars. Therefore, as a simple incineration treatment has been gradually restricted. As plastic has the highest energy value in MSW, with an average energy content of 4400~11000kcal per kilogram, it is increasingly valued as a heat energy recycling. Japan and some European countries mainly generate electricity by incineration, while Belgium and other countries supply industrial steam by incineration. In addition to being used as heat energy, Japan is also used as solid fuel for iron making. They believe that incineration and recycling of heat energy is an important means of recycling plastic waste, and also the most realistic choice for MSW treatment. In the United States, incineration treatment has long been opposed by environmental protection departments, who believe that the gases emitted by incineration are harmful to national health, and that in the long run, incineration treatment is still a wasteful use of available resources. In addition, due to the high investment in gas separation devices and acid removal equipment necessary for incinerators, the disposal of residual ash will also increase the incineration cost, resulting in the high cost of incineration to recover heat energy. Therefore, the proportion of incineration treatment in the United States is much lower than that in Western Europe and Japan. However, over the past decade, the United States has also paid great attention to the incineration of heat energy recovery

4.3 recycling

the recycling of plastic packaging waste is considered to be a good method that can better control environmental pollution, effectively use resources and save energy. It is reported that compared with new raw material products, recycled plastic waste products can save 85-90% of resin production energy and 6-17% of processing energy. However, due to historical conditions and technical and economic factors, the proportion of recycling in MSW treatment is still low. One of the main problems is that a reliable and effective recycling channel has not yet been formed; Second, the plastics in MSW are too dispersed, the components are mixed, and the separation and sorting technology is difficult; Third, the cost of recycling is high. It is reported that the cost of recycling plastic waste in Germany is 340 US dollars per ton, 528 US dollars for sorting and 400 US dollars for cleaning. In addition, there are also some problems in the product direction and value of recycled materials, resulting in a low proportion of recycling. Although there are still many problems in technology and economy, recycling is not only conducive to environmental protection, but also of great significance from the perspective of saving the earth's limited resources and effectively using renewable resources. Especially in the 21st century, mankind is facing more severe challenges from resources, energy and environmental issues. In order to get rid of the plight of resource scarcity, energy crisis, environmental pollution and other issues, people are increasingly aware that the recycling of plastic waste is not only to bring economic benefits, but also more importantly, social and environmental benefits. Therefore, the treatment direction of plastic waste is gradually shifted to the development and utilization of renewable resources and secondary resources, The progress of science and technology has also created conditions for recycling. At present, many countries are gradually establishing a set of recycling management systems from legislation, recycling, production, inspection, sales, etc., and studying and developing a variety of recycling technologies, such as recycling technology, recycling technology, pyrolysis technology, oiling technology, incineration and heat recovery technology, composting technology, etc., are in the ascendant. Recycling has become an imperative development trend of the plastic industry. According to the prediction of relevant experts, the proportion of plastic waste recycling in plastic waste treatment will rise to more than 40% at the beginning of the 21st century, of which recycling and recycling will account for 42%, incineration recycling energy will account for 26%, pyrolysis and oiling recycling chemicals and fuel oil will account for 25%, and other 4%

4.4 composting treatment technology

although composting is an ancient and traditional method of using materials and designs in manufacturing and processing to treat domestic waste. However, with the progress of technology and the development of biodegradable plastics, it has only begun to be recognized by European and American countries as a feasible method to deal with large-scale MSW in recent years. In the planning of the European community, composting is regarded as a way of recycling packaging materials, that is, reusing organic waste to improve the soil, and the Federation of organic recycling and composting (orca) has been established. The Federation has issued documents on Composting in the name of European government departments and legislative authorities, discussing that the composting of MSW can not only be used as a supplement to the threatened soil, It also helps to prevent the gradual decline of soil quality in the European continent. Under the guidance of the new waste disposal regulations, Germany, Britain and France also began to take composting as a recycling method. According to the relevant report published by Frankfurt Institute in Germany a few years ago, at present, about 15 cities in Germany adopt composting method to treat the organic components in MSW. Germany is widely promoting the application of composting system, and suggests that the composting of biodegradable packaging materials should be considered as equivalent to their recycling, This will make it easier for customers to achieve the recycling goal required by the packaging industry in the relevant national waste treatment legislation. France has more than 100 sets of composting equipment. These devices can process 1800kt of household mixed waste every year, thus producing 700kt of composting products. At present, composting technology is gradually becoming practical, and further improve composting equipment and sorting and treatment technology, establish corresponding quality standards through identification and monitoring system, so it is considered as a treatment method with development potential

4.5 degradable plastics

the research and development of degradable plastics can be traced back to the 1970s. At that time, in the United States, plastic beverage bottle lifting rings and agricultural films were discarded in the field after use, which not only affected the beauty of the environment, but also endangered the lives of wild animals, so they were criticized and denounced by the environmental protection department. For this reason, research on photodegradable plastics was carried out. In the 1980s, starch filled "biodegradable plastics" were developed, boasting that they can be rapidly biodegradable under the action of microorganisms in landfills or soil. They were introduced to the market one after another and became popular. However, after several years of application practice, it was proved that this material did not obtain convincing biodegradation effect and was accused of exaggerating propaganda False propaganda was strongly opposed by the environmental protection department. Since the 1990s, great progress has been made in the technology of degrading many customers' plastics who come here to send packages, and many new varieties have been developed, such as light/biodegradable plastics, photothermal degradable plastics, starch blend degradable plastics, water-soluble degradable plastics, fully biodegradable plastics and so on. Since entering the 21st century, biodegradable plastics, especially biomass plastics, have been paid more attention and further developed in line with the policy of environmental protection and sustainable development

Although great progress has been made in degradable plastics, in general, the technology of degradable plastics needs to be further improved, the performance needs to be further improved, and the cost needs to be further reduced. Its role in the environment should be correctly evaluated

· degradable plastic is a member of the plastic family. It is not only required to maintain or have the characteristics of ordinary plastic before use, but also required to degrade rapidly under natural environmental conditions after use. Stability and degradation are a pair of contradictions, but it is required to realize in different stages of the same product, which is very difficult, and it is a high-tech product

· degradable plastics are only suitable for specific application fields and some plastic products, such as disposable packaging materials, mulch films, medical and sanitary materials, because of their degradable function. These products are seriously polluted and are not easy to recycle, or even if they are forcibly collected and used, they have little or no benefit. Therefore, the use of degradable plastics can reduce the volume of garbage, so as to achieve the purpose of reducing environmental pollution

· at present, some degradable plastics entering the market belong to destructive degradation, which cannot be degraded rapidly or completely, but under certain environmental conditions and within a certain period, they can deteriorate and disintegrate into fragments (debris) that are easy to be absorbed by the environment. With the passage of time, they can finally enter the natural cycle. Fully biodegradable plastics can be quickly and completely biodegradable into CO2 and water under certain environmental conditions. Combined with composting treatment methods, as a supplement to recycling, it is considered to be a good way to control environmental pollution caused by plastic packaging waste, and is the current international development direction

· the research, development and application of biodegradable plastics, whether from the practical point of view of the earth's environmental protection or from the gradual replacement of inexhaustible renewable resources, is decreasing, and each piece of non renewable petrochemical resources increases by about 0 2 dollars and from the strategic height of implementing the direction of sustainable development are of great significance

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