Plastic, having appeared in mass consumption only 60–70 years ago, radically changed a person’s life: it expanded the boundaries of the possible in design and industry and made previously expensive goods available. At the same time, it became one of the most serious environmental problems of mankind. The main advantages of plastic - durability, strength and low price - have turned into its main disadvantages (1). According to the United Nations Environment Agency, about 300 million tons of plastic are produced annually in the world, half of which are disposable items, mainly food packaging. Of this colossal amount, only 14% is collected for processing, and only 9% is actually processed; 12% is burned with the release of toxic substances. The remaining 79% is dumped on landfill or, even worse, illegally dumped into the oceans. Plastic is the third largest raw material used in the US manufacturing industry, producing 19.5% of the world""s plastic items. “The level of recycling plastic waste in different countries is different. For example, in Germany, unlike the United States, one of the highest rates of plastic waste recycling is observed - about 48%, while in the United States it’s only 9%,”says the director of the educational project The Create Trust, Graham Peebles (2). At the same time, it should be noted that the level of selection to a large extent depends on the general culture and discipline of the population, as well as the fact that plastic packaging materials are difficult and expensive to recycle. Since various resins cannot be mixed, plastic materials must not only be sorted, but also processed separately. This time-consuming process significantly increases the cost of processing. Thus, many companies cannot use them because of their low quality and poor composition compared to products derived from primary raw materials. Therefore, plastics that have been recycled can find only limited use (3, 4). In addition, plastics, when buried, do not decompose for many tens and hundreds of years, and, when combustion, pyrolysis or gasification emits a significant amount of harmful substances. At the same time, chlorine-containing plastics (for example, polyvinyl chloride) decompose completely with the release of extremely toxic organochlorine compounds: polychlorinated dioxins, furans and biphenyls (5, 6). Hope for a better environmental footprint was pinned on the development of biodegradable bags and disposable tableware, but instead more problems were made. Biodegradable plastics consist of corn starch, polystyrene, and an additive that turns the material into powder. Products made with traditional polystyrene can be removed from the waste stream and processed. However, polystyrene dust, into which “biodegradable” plastic breaks down, is not only impossible to remove from the garbage stream, but because of its size, can also “migrate along the food chain and end up in our plates.” At the same time, environmentally-controlled burning of biodegradable materials is not acceptable, as it leads to the release of harmful substances as well (7,8). In this regard, the use of many types of plastic packaging materials is prohibited in many states and other countries. Meanwhile, during the coronavirus pandemic, the desire to minimize the risk of infection has led to an increase in the demand for disposable plastic items, by both households and the medical industry. Experts worldwide have repeatedly stated that disposable plastic can reduce infection risk. Home delivery of food and products has caused in increase in disposable plastic packaging. “During a pandemic, a return to a one-use one is dictated more by fear than common sense,” said Roman Sablin, eco-trainer, eco-consultant, co-founder of the Green Driver educational organization. (9). At the same time, Tony Radoszewski, President and Chief Executive Officer of the American Plastics Industry Association, in mid-March 2020 requested the U.S. Department of Health and Human Services to lift bans on the use of disposable plastics, which have been operating in several states for several years. The expert called plastic the safest material for packaging and transporting products and noted that reusable items, including shopping bags, can become a big source of infection. The increase in the number of diseased provoked a rollback of anti-plastic campaigns around the world. The Governor of the US state of Maine, Janet Mills, postponed until the beginning of 2021 the ban on the use of plastic bags, which was to enter into force on April 22. The authorities of Brooklyn, a city in the state of Massachusetts, have temporarily suspended a ban on polystyrene containers (in force since 2013) in an effort to support restaurant owners who can only sell takeaway food at the moment. The Canadian coffee shop chain Bulk Barn has ceased to serve visitors with reusable mugs. “Due to the precaution associated with COVID-19, we decided that at this stage it is appropriate to be vigilant and to suspend the reward program for visitors with refillable containers,” the company spokesman admitted.
In addition to the virus effects, proper packaging, including plastic, can extend the shelf life of products, helping to reduce the problem of food waste. A study conducted by Swedish scientists found that, with the right choice of packaging, 20–25% of food waste can be avoided. According to the Higher School of Public Administration of Moscow State University, flexible polymer packaging allows an increase in shelf life of products by 1.5-10 times. Estimates by the Food and Agriculture Organization of the United Nations and the research organizations Boston Consulting Group and World Resources Institute suggest that if plastic packaging is wholly rejected by 2030, global food waste losses could reach 2.1 billion tons. Such a quantity of waste would lead to the formation and release of about 8% of all greenhouse gases on the planet, while 870 million people still face the threat of hunger. According to estimates by the Scottish environmental organization Zero Waste Scotland, the carbon footprint of produced food waste is three times that of plastic waste (10). “The plastics industry has taken advantage of this pandemic to try to convince people that disposable plastic is essential for our safety and reusable is dirty and dangerous,” said John Hocevar, director of the Greenpeace Ocean Campaign. The increase in disposable plastic is a major blow to the fight against plastic pollution, which, according to the forecast of the World Wildlife Fund, will increase by 40% in the next decade. “As our understanding of the effects of plastics on the health of our planet and our communities continues to grow, it becomes increasingly clear that we need to quickly abandon disposable plastics,” added Michael Oshman, General Director of Green Restaurant Association (11).
As the co-founder and director if the “Epoch of the Anthropocene” project, Dmitry Burenko has said that a temporary refusal to utilize reusable items in the pandemic situation is a timely and reasonable measure. “The main priority now is to save human lives and minimize the risk of spreading the virus, and if this requires a temporary refusal to use their own mugs by café visitors, this is not the biggest sacrifice,” he explains. We must not forget that plastic in and of itself is not bad – the problem is that we do not know how to collect and recycle it and therefore it ends up in landfills, forests, and oceans. It is essential to “close the loop” of the plastic cycle such that useful products are produced again from the assembled and recycled plastic. Denkstatt Gmbh, an international consulting company, believes that the involvement of plastic in a close-loop economy will contribute to the rational use of resources and the reduction of greenhouse gas emissions. Accordingly, the production of polymer materials may be characterized by lower specific indicators of environmental impact when compared to alternative materials when appropriate recycling processes are used. For example, one can use technogenic waste and byproducts from oil companies as a raw material for plastic production, such as petroleum gas, which would otherwise be flared off and would release large amounts of atmospheric pollutants and CO2 (10).
At the moment, many companies are developing new packaging solutions, organizing lines for sorting and processing plastic materials, and, in some cases, are switching to reusable containers. The efforts of environmental organizations like the World Wide Fund for Nature (WWF), Greenpeace, and many others continue to actively inform people about the importance of an environmentally friendly lifestyle (10). However, the dispute between supporters and opponents of the ban on plastics continues. The solution of the problem has come to a standstill, since each side almost equally brings its positive and negative arguments. A need arises an urgent need for the joint processing of all types of plastics, that is, in the processing of plastics without preliminary sorting.. It turned out that scientists and engineers from many countries have been working on the creation of these technologies long since. This is plasma gasification of industrial and household waste and pyrolysis of garbage (and plastic) in an oxygen-free environment at lower temperatures than plasma. Why are these technologies advancing very slowly on an industrial scale? Discussion of political and marketing issues is beyond the scope of this study, but one can consider the main advantages and disadvantages of these technologies.
A significant advantage of the plasma method in comparison with the incineration of solid waste (and plastic) is the environmental cleanliness of the technology: the appearance of harmful emissions such as dioxins or furans is excluded. The temperature level of 1300 - 1600 њ C allows you to decompose all complex substances into protozoa. No sorting of solid waste is required: all types of organic waste, including all types of plastics, are destroyed in a single plasma shaft furnace. Slag is vitrified upon cooling and, according to the authors, also does not contain harmful substances (mainly heavy metals) (12, 13). However, a kind of “encapsulation” of toxic substances in vitrified solid waste slag is not always possible and, accordingly, toxic metals under certain conditions (for example, if mechanical treatment is needed during further use - crushing, grinding, etc.) can be released from the ground slag , especially when washed away by rain (14, Section VI. Toxicity of slag and fly ash).
There are no reliable arc plasma torches with a sufficient resource of continuous operation. Their work is characterized by a high noise level (up to 120-130 dB), high energy consumption (processing of one ton of solid waste requires 500 kW * h of electricity), as well as high operating costs for servicing plasmatrons and reactor repair. Even with low productivity, the cost of building these plants is high (13). The resulting gas fuel contains heavy metals. This is explained by the fact that mercury (Hg, evaporation temperature 357њC), cadmium (Cd, 765њC), zinc (Zn, 870њC) and bismuth (Bi, 1564њC) at a temperature of up to 1600њC enter a gaseous state, are part of volatile products and the resulting synthesis gas, and then into the combustion products and the environment. In addition, this gas fuel, unlike liquid fuel, is difficult to transport and therefore, as a rule, it is used directly at the place of its production for the production of heat and electric energy in adapted gas-piston power units, which is not always economically feasible (15). It is known that food waste fundamentally was not burned, since they contain sodium chloride containing chlorine (6). This fully applies to the plasma method, which is also not suitable for the processing of composted waste. The fact is that at a melting point (801њC) in the NaCl melt, thermochemical dissociation of salt occurs - the substance decomposes into ions: NaCl = Na (+) + Cl (-).The high chemical activity of the resulting chlorine leads to the instant formation of new toxic / hazardous substances directly inside the synthesis gas stream, and then the flue gas, which pollutes the environment when emitted from the chimney (16), unless, of course, expensive cleaning of flue gases from heavy metals, chlorine and its derivatives is not provided. Currently, small plasma furnaces, designed for the processing of 100-200 kg / hour of waste, for the destruction of particularly toxic substances, for example, medical waste, are most in demand. There is still no debugged production of large plants based on the plasma method. A household waste recycling plant in Canada is still in the “setup” phase. Market promotion of electroplasma innovative technologies needs scientific support of pilot production and their commercialization. In accordance with the foregoing, effective mechanisms of state support for investors should be worked out at the stage of design capacity development (13).
Some companies are moving from simple waste incineration to a two-stage process, including a pyrolysis step followed by incineration. From an energy point of view, the main products of pyrolysis are gas and liquid, in this regard, pyrolysis is one of the most effective processes for processing waste into energy. Liquid pyrolysis products are the most valuable products due to the convenience of storage, transportation and versatility in their application in boilers, internal combustion engines, furnaces, gas turbines, etc. (17). Such a process turns out to be energetically more profitable than simple combustion and the plasma method; moreover, it is also suitable for the treatment of composted waste. Pyrolysis produces gas and a solid pyrolysis residue. Then the one and the other products immediately, without any additional processing, are sent to the firebox for combustion to maintain the process. Part of the pyrolysis gases after condensation can be removed from the system and used as liquid fuel by other consumers. At the same time, however, the same disadvantages are observed as with direct waste incineration. In those cases when the pyrolysis gas is purified from hydrogen chloride, highly toxic dioxins, furans, biphenyls, sulfur compounds, heavy metals, methane, organic volatile foul-smelling substances and other components, the process becomes as expensive as with direct combustion. Therefore, now, on an industrial scale, this technology is practically not being advanced, and in comparison with incineration it makes up only a small part of the total volume of solid waste processing.
Thus, even the most modern technologies do not provide cost-effective, self-sustaining, joint processing of all types of plastics and municipal waste. And none of the existing technologies provides for the purification of these wastes from heavy metals and dioxins in the main production process, i.e. so far no generalizing technical solution has been found that ensures the joint processing of all types of plastics and municipal solid waste of any morphological composition without sorting, risk to nature and humans.
The way out of this situation and, accordingly, an effective solution to the problem, it seems to me, is possible only as follows. At the places of formation and / or at the existing sorting complexes, it is necessary to select only that amount of uncontaminated material that is necessary for the stable operation of the recycling industry, including the effective marketing of manufactured goods. The remaining unsorted municipal waste, plus an unlimited amount of additionally delivered any types of plastics, goes to plants whose technology and equipment are presented in the Technological Regulation developed by the author for the production of liquid fuels and other related commercial environmentally friendly secondary products, the sale of which is always ensured regardless of the market situation. Excerpts from its several sections are presented in (18). Commodity products produced are: liquid fuel, scrap of ferrous and non-ferrous metals, a mixture of various types of cullet (or glass powder), slag and slag concrete products purified from heavy metals, sulfur and glass, dry calcium chloride, liquid carbon dioxide, non-ferrous and precious metal concentrate obtained from electronic, electrical and cable scrap. Such a decision will exclude dumping of any plastic materials and products into landfills, which will allow not only to exclude administrative restrictions, but also, if necessary, to increase their production and assortment in the sizes necessary for the population and industry.
The technology for the production of liquid fuel is patented and carried out by the method of low-temperature pyrolysis with limestone additive. In the first stage of pyrolysis, halogen-containing components, for example, plastics, containing chlorine (primarily PVC products: linoleum, wallpaper, window frames, drainage pipes, plastic containers, etc.) are completely decomposed at a temperature of 200 - 250oу (390 - 480oF) with the release of hydrogen chloride, which is neutralized by limestone with the formation of calcium chloride. At the same time, sulfur compounds contained in municipal waste will also be neutralized by limestone. During the second stage of pyrolysis, the pre-treated waste is heated to a higher temperature of 500oC (930oF), sufficient to decompose other organic substances contained in the waste. At the same time, polychlorinated dioxins, furans and biphenyls are not formed due to the fact that all chlorine from the treated waste was removed at the previous pyrolysis stage. In addition, the absence of air and, accordingly, free oxygen completely eliminates the occurrence of combustion processes in the furnace drum, which ensures the composition of the gas mixture is practically insensitive to possible fluctuations in the composition of the initial solid waste. Thus, if, in known processes, the pyrolysis gases obtained during waste treatment are cleaned using special gas purification equipment, the proposed process takes measures to ensure that highly toxic and hazardous products do not form at all in the volume of the pyrolysis furnace, i.e. conditions have been created to prevent the formation of dioxins, which is much simpler than binding molecular chlorine, let alone destroying dioxin. Gases generated during pyrolysis, as well as vapor from the equipment, condense. Water condensate is used in a system for extracting water-soluble salts and heavy metal ions from a solid pyrolysis residue. The non-condensable part of the pyrolysis gas together with part of the condensed liquid organic products is sent to the furnace for co-combustion with solid pyrolysis residues washed from heavy metals (coal-mineral composition). The remainder of the liquid organic products (pyrolysis oil) is removed from the system as commercial synthetic liquid fuel. At the same time, serial, easily accessible equipment is used, all processes are continuous and fully automated. The capacity of the enterprise can vary widely, since production consists of separate autonomous technological lines (modules). Even without assessing the prevented damage to the environmental and with the free reception of municipal waste and plastic for processing, the payback period for the construction of the plant only due to the production of environmentally friendly products is less than a year. This project is especially important for countries experiencing problems in the disposal of plastics, fuel shortages, for hot and arid areas with water shortages and cold areas where frozen waste can be possible delivered to the plant. The design decisions and calculations presented in the Regulation for real industrial conditions show that the municipal waste thermochemical processing plant will efficiently process both composted and non-composted solid household waste of any morphological composition in conjunction with an unlimited number of additionally loaded any types of unsorted plastics without risk for nature and man.
Conclusions.
The dispute between proponents and opponents of the ban on plastics continues ... Some believe that before the outbreak of the coronavirus, cities and states made some progress in banning plastic bags, moving from disposable plastic - which ultimately ends up in a landfill or, even worse, in the ocean - to paper or products reusable. In addition, they are confident that the plastics industry has taken advantage of the pandemic to try to convince people that disposable plastic is necessary for our safety, and reusable is dirty and dangerous. Others believe that modern society lives in the world of plastic and it is impossible to ban it. This is especially true for disposable flexible polymer and other plastic packaging of food products, which can significantly increase the shelf life of these products and minimize the risk of infection of the population. In this case, the carbon footprint in the processing of plastic packaging is several times smaller than the carbon footprint from food waste produced. In addition, the level of constant threat of hunger of a significant part of humanity is reduced. To the same extent, this also applies to medical items and plastic packaging, which provide a significant reduction in the risk of infection of the population. The solution to the dispute and the problem are at come an impasse.
Modern technologies (plasma method and pyrolysis) do not provide cost-effective and environmentally efficient joint processing of all types of unsorted plastics and municipal waste i.e. no generalized technical solution has been found so far that ensures the joint processing of all types of unsorted plastics and municipal solid waste of any morphological composition without pre-sorting, risk to nature and humans.
The proposed approach to the recycling of polymer wastes ensures the involvement of plastic in the closed cycle economy due to the receipt of useful products from used plastic. Thereat eliminates environmental pollution from emissions of highly toxic substances. And it is very important that this technology ensures their joint processing with unsorted solid municipal waste of any morphological composition.
At the places of formation and / or at the existing sorting complexes, it is necessary to select only that amount of uncontaminated material that is necessary for the stable operation of the recycling industry, including the effective marketing of manufactured goods. The remaining unsorted municipal waste, including plastic, plus an unlimited amount of additionally delivered any types of plastics, goes to plants whose technology and equipment are presented in the Technological Regulation developed by the author for the production of liquid fuels and other related commercial environmentally friendly secondary products, the sale of which is always ensured regardless of the market situation. Excerpts from its several sections are presented in (18). Commodity products produced are: liquid fuel, scrap of ferrous and non-ferrous metals, a mixture of various types of cullet (or glass powder), slag and slag concrete products purified from heavy metals, sulfur and glass, dry calcium chloride, liquid carbon dioxide, non-ferrous and precious metal concentrate obtained from electronic, electrical and cable scrap. This project is especially important for countries experiencing problems in the disposal of plastics, a shortage of fuel, for hot and arid regions with a shortage of water and cold regions where it is possible to deliver frozen waste to the plant. Such a decision will exclude dumping of any plastic materials and products into landfills, which will allow not only to exclude administrative restrictions, but also, if necessary, to increase their production and assortment in the sizes necessary for the population and industry.
List of references.
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17. Tikhonov A.V., Sulman M.G., Kosivtsov Y.Y., Lugovoi Y.V. Pyrolysis as a modern method of obtaining alternative energy sources. Tver State Technical University. Vestnik_TvGU._Seriya_Khimiya._2015 ._2._Page 45 - 51 / http: //docplayer.ru/78616484-Piroliz-kak-sovremennyy-metod-poluchen ...
18. Excerpts from the “Technological regulations, initial data and recommendations for the design of a plant-module for the thermochemical processing of municipal waste” / http://www.new-garbage.com/?id=13695 and http://www.new-garbage.com/?id=13696.
Recycling plastics waste
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