Role of Environmentally Degradable Plastics

In Environmental Protection and Sustainable Development

By Saizhen Tang and Xin Tao

(Special Committee of Degradable Plastics, China Plastics Processing Industry Association 100088)

Abstract: This article gives a general introduction of two major problems––– environmental protection, sustainable development and plastic wastes treatment. As we know, environmental protection and sustainable development have developed to be a global focus and urgent affairs; and plastic wastes have become an environmental crisis. From the viewpoints of decrement, resource recycle, harmless treatment, resource replenishment and substitution as well as the whole lifecycle analysis(LCA), the article elaborates on roles of environmentally degradable plastics (EDP) in environmental protection and sustainable development.

 Key Words:     Resources,      Environment,       Sustainable Development,        Degradable Plastics, Wastes, and Roles

Environmental Protection and Sustainable Development – a focus and urgent thing for us to do in the 21^st century ^[1]

Since the middle and end of the 20^th century, an increasing number of countries in the world have successively walked into the way of development that is manly characterized by industrialization. The economic development mode of high investment, high output and high consumption promotes the rapid development of economy, and creates unprecedented large material wealth while speeding up the evolution of world civilization. However, there arise a lot of problems accordingly, such as reckless exploitation and excessive consumption of global resources. As a result, ecological environment is sharply destroyed and increasingly deteriorating, and human being has a more and more strained relation with nature. Confronted with the severe situation, all countries in the world, both developed and developing countries, are forced to rationally pursue new development mode and strategy, and seek a brand-new way of development, in which economic growth, social development and environmental resources will progress harmoniously and form virtuous circles. Under such circumstances, the way of protecting global environment, building circular society and implementing sustainable development is put forward.

As yet, there is no internationally consistent definition and accepted theoretical basis to the word “sustainable development” in the world. But all kinds of definitions and explanations are common in fundamental ideas. A widely used definition of the word in the world is the one given in the document Our Common Future drafted out by G. H. Byundland, President of the World Committee of Environment and Development (WCED). That is, “Sustainable development” is the development that meets the needs of the present man without compromising the ability of future generations that meet their own needs. This definition was accepted and identified in the Declaration on Sustainable Development approved on the 15^th Council of the United Nations Environment Programme(UNEP) in 1989. Later, Some scholars extended the definition of sustainable development in technology selection: “Sustainable development turns to cleaner and more effective technology, and aims to achieve ‘zero discharging’ or sealed type technical process and decrease consumption of energy resources and other natural resources as far as possible.” Agenda in the 21^st Century, an important document approved in the United Nations Congress of Environment and Development in 1992, is an action plan on sustainable development in the scope of the world. This document put forward a series of guidelines on the sustainable development of industry. It aims to create an action principle for all countries in the 21^st century on the issue that human activities leave an influence on environment, and provide a strategic framework on global measures, to ensure a common future for human being.

Sustainable development is a comprehensive concept related to economy, culture, technology and resource environment. It is a strategy and mode on long-term development of human being, put forward on the basis of environment and natural resources, and also a symbol of harmonious development among economy, society and environment.

With the coming of the 21^st century, in the future economic development, the world will be much more confronted with the severe challenge of increasing population, lacking of resources and deteriorating environment. This result in two highlighted problems: to economically and properly use limited nonrenewable resources, and to ensure the secure living environment for human being, maintain a clear and clean living space. Therefore, to protect the environment of the earth and implement the sustainable development has become the principle for development of all trades and human activities, and becomes a focus of the world and urgent affairs.

 Severe Challenge for Plastic Wastes on Environment Problems

As a new material characterized by excellent all-round properties, low price, easy molding and manufacturing, plastics now have been widely applied in departments of national economy and fields of people’s life. They not only make up the deficiency in quality and quantity of traditional materials, but also become indispensable material for technical process of some related industries. Although plastics will continue to function as a platform of economic development in the future, there are some problems that need to be solved. The first one is the environment problem of plastics. Plastic wastes are difficult to degrade in natural environment, and especially disposable plastic wastes characterized by large quantity, scattering, dirty, disorder appearance and uneasy to collect. Part of them are collected through municipal solid wastes (MSW) processing systems while the rest, however, are aimlessly discarded and scattered on the ground, mountains, in rivers and lakes. It brings pollution to the appearance and landscape of a city, destroys ecological balance, and even endangers lives of livestock and wildlife. Because of this, environmental protection departments of many countries and the public blame this bad behavior. For ten years, some developed countries and regions, including European countries, USA and Japan, have successively drafted out a series of relevant laws and regulations. As these laws and regulations stipulate, those plastic materials and articles--especially the non-recoverable disposable plastic products-- which are difficult to process or degrade, or may produce harmful substances, are prohibited or restricted in part, or compulsively collected. In addition, these countries and regions have formulated recovery objectives and proportions to such plastic materials and articles, and have stipulated to collect pollution fees or levy high tax to them.

China’s plastics industry has a late start in development. According to statistics of relevant departments ^[2], the plastic raw materials in 2001 were 12038.5kt in output and 14260kt in import quantum. The total output of plastic products of all state-owned enterprises and non state-owned industrial enterprises (of independent accountability that had an annual sales income of over RMB 5,000,000) was 11835kt in 2001. If that of medium and small-size enterprises were to be counted, the national output of plastic products would reach more than 20,000kt in 2001. If the disposable plastic products, which are difficult to recover, accounted for 20%, the plastic wastes would reach 4,000kt.

According to undercount, in recent years, the daily consumption of fast food throwaway containers used in Beijing, Shanghai and Guangdong Province and other provinces and cities has achieved more than 1,000,000 respectively; if the throwaway trays were counted, the daily consumption would almost reach to 1,000,000,000. According to statistics, in Shanghai in 1999, plastic wastes which were blended with domestic garbage reached to 360kt, which accounted for 14% of the quantum of municipal solid wastes (MSW); the daily consumption of plastic wastes in Beijing was about 0.9kt per day, and the annual consumption was about 330kt.

According to statistics, in China in 2000, the MSW exceeded 140,000kt and increased by 8%. If the figure of 4,000kt of disposable plastic wastes should be adopted, the national annual disposable plastic wastes would account for about 3% of MSW in weight, and for 30% in volume. The present management of wastes in China leaves a lot of problems. For example, except for several large cities, such as Beijing, Shanghai and Shenzhen, which have a certain number of sanitation processing equipment and modernized incineration systems, a lot of other cities usually pile up wastes in the open air or landfill them simply when they process wastes. In addition, people’s environmental consciousness is relatively low. It is common that wastes are dispersed and garbage is emptied and thrown willfully. For these reasons, the negative influence to the environment is increasingly serious, and it is dramatically compared to “white pollution”, and is blamed to a large extent. From 1996, the Ministry of Railways has stipulated that polystyrene food containers be forbidden in trains. Local governments in a dozen of cities, such as Hangzhou, Wuhan and Guangzhou, followed its steps to promulgate prohibition regulations. In 1999, the Ministry of Economic Trade and Cooperation promulgated the 6^th ordinance ordering that polystyrene food containers be no loner produced and used in the whole country. Some cities, such as Beijing, Tianjin, Dalian, Hainan and Shijiazhuang, went farther to prohibit and restrict the using of common plastic bags. No doubt, the foregoing actions are a severe challenge to the development of plastic materials.

Roles of Environmentally Degradable Plastics in Environmental Protection and Sustainable Development

As has been stated above, extensive use of plastic materials results in the increasingly serious burden of environment. For ten years, a lot of researches have been made and many schemes and measures proposed in domestic and overseas, such as decrement, recycle, and development of environmentally degradable plastics. In practical operation, however, there exist considerable difficulties and many key problems that need to be researched and solved. Moreover, obvious effect can only be attained if the above-mentioned measures supplement each other and are combined organically into a scheme that combines prevention and control, and makes overall control.

There are a lot of special articles, which have discussed the importance of decrement, recycle and so on in control of environmental pollution and implementation of sustainable development. Therefore, this article will be based on Methods on Control of Pollution of Solid Wastes. It will make a concise analysis and commentary on roles of environmentally degradable plastics in environmental protection and sustainable development, from points of decrement, resource recycle, harmless treatment, resource replenishment and substitution and the whole lifecycle analysis of products.

1.    Decrement

Decrement refers to the decrease in consumption of resources and output of wastes in the production of plastics. By now, China has developed and commercialized photo-oxygen degradable plastic film, sheet, bag, box and so on, which are made up of highly starchy biodegradable plastics or highly inorganic materials (such as calcium carbonate). The starch content or calcium carbonate content of these products is 30% - 60%. This means that 30% - 60% of plastic raw materials may be saved. Furthermore, one third or one half components can be biologically degraded or environmentally dissolved easily. This means that one third or one half output of wastes can be reduced. On this basis, it is believed that this is in full conformity with what the technology of cleaning production is about, i.e. by replenishment and substitution of pressed resources, to save limited resources, cut down sources of production and reduce output of wastes, and thus make contribution to implementing the environmental protection measures in saving resources and decreasing pollution, and the strategy of sustainable development.

2.    Resource Recycle

Resource recycle refers to recovery and recycle of plastic wastes. Resource recycle of solid wastes includes 3 measures, i.e. material recovery, material conversion and energy conversion. EDP is not suitable for material recycle, but has little difference in its effects of energy conversion such as recycle of heat energy or electric energy upon burning treatment, or when utilized as fuel in blast furnace. Composting is a form of material conversion. It is proven in foreign practices that composting of biodegradable plastics (BDP) is a particular way of recovery and recycle, and that the combination of EDP and composting is one of the best ways to control plastic wastes and environmental pollution. As for the MSW treatment methods in foreign countries at present, staffing treatment and burning treatment are dropping in proportion because of shortage of landfilling ground and production of harmful gas; composting method, on the other hand, becomes a focus of the world because it can not only make full used of organic materials and pressing soil replenished, but also help to prevent the decreasing quality of farmland soil resulting from long-term using of chemical fertilizers. Some countries, including European countries, USA, Japan and so on, are making experiments on composting of biodegradable plastics and have formulated authentication standards and mark. It is proved in these experiments that biodegradable plastics fully meet the requirements of composting quality. Because of high price, it cannot be accepted in the market in a short while. It needs time for promotion and application. The high-starch content biodegradable plastics, which are produced in China, almost equal the common plastics in application performance and price, and have a good degradation effect. Now they are in composting field experiment. It is shown in the initial experiment that the PE plastic film (bag) on which low temperature heat oxidant and other degradation accelerant are added, with more than 40% starch content, can be broken into fragments and even powders within 1 – 3 month(s) during the period of composting. For ten years,  China Academy of Agricultural Science has made some tracking experiments on degradable mulching film and some researches on chemical pollution as well as physical pollution to the soil. It is shown in the results of these experiments and researches that degradable mulching film has no obvious influence on N.P.K in soil, and has no the findings that it brings pollution of heavy metallic elements (such as chromium and cadmium) to soil, nor does it form accumulation of microelements, such as cobalt, copper, nickel and molybdenum. As for the dumped mulching film that has collapsed into fragments (less than 16cm²), its accumulated residual quantity of 20 years has little possibility of pollution to soil in capacity, specific gravity, water movement, pores and aggregate, and has no adverse effects on growth of crops. It is estimated upon the above material that it may meet requirements of composting, but its result needs to be convinced by the final results and data of experiments.

3.    Harmless Treatment

Harmless treatment refers to that plastic wastes are easy to be made harmless or to be dissolved environmentally, so that the adverse effect of plastic wastes on environment is decreased to a minimum. Up to present, China has developed and produced a lot of plastic products (plastic film, sheet, bag, box, etc.), based on technologies of photo degradation, photo biodegradation, photo-oxygen biodegradation, high-starch biodegradation, high calcium carbonate photo-oxygen degradation and so on. After laboratory tests, field soil landfilling and composting tests and farmland coverage pilot tests, it is proved that these plastic products, under certain environmental conditions, may crack or break into fragments or even powders or something that keeps the original form but are broken into pieces with a touch which can be easily dissolved in the environment, within a certain period (20 days to a minimum and hundreds of days to a maximum), and may return to nature cycle with the time passing by. Their cycle is longer than that of natural materials or biodegradable plastics, but is shortened to a large extent as compared with those nondegradable plastics products, so that volume and quantity of plastic wastes are decreased and the purpose to reduce environmental pollution and relieve environmental contradiction is achieved.

In addition, in the course of harmless treatment of MSW, as compared with ordinary plastics, EDP has little influence on heat recovery, except that it has a certain influence on material and chemical recovery. In addition, it is favorable to landfill and burning treatment as the wastes are easily degradable, require less land, and have a lower temperature which means longer furnace life.

4.    Resource Replenishment and Substitution

It can be seen, from the development of plastics industry in the world since 1950s, that raw materials of the plastics industry mainly came from fossil fuels resources (coal, petroleum and natural gas). According to statistics, now the resource of plant/crop base has little share in the chemical industry of the world, and energy resource accounts for less than 1% in the industry and raw materials less than 5%^[3]. For example, the output of plastics in the USA has been more than 30,000kt, in which the output of the plastics adopting plant/crop base as raw materials only accounts for 1.8%. It is well known that fossil fuel is a limited resource, which is decreasing and facing the danger of exhaustion. According to some specialists, the fossil fuel resource which can be exploited and can be verified in reserves can only sustain for 50 - 100 years more ^[4]. According to the report from Japan materials, petroleum in the world can only be exploited for 45 years and natural gas 63 years. It must be noted that, with the growth of population and improvement of living standards of people in the developing countries, the above mentioned service lives will be further limited, though new mineral resources may be found in the future. Therefore, as for the development of the plastics industry, the limited resources are worrying. Now the governments and industrial circles of developed countries in Europe and America are researching and formulating the strategy on using the renewable resources to replenish or substitute fossil fuel resource, which is nonrenewable and decreasing. For example, the USA has formulated the strategic assumption and objectives on development and application of renewable resources, suggesting that at least 10% of chemical basic products in 2000 come from the renewable resources which take plant/crop base at raw materials, and the proportion will increased to 50%^[4] in 2005. It also proposes in the assumption that, however applicable the technology may be, to converse the existed resources into renewable resources is in conformity with the development trend of sustainable development and is suitable for environmental and ecological development. One of the successful examples about the substitution of renewable resources to nonrenewable resources is that of the biodegradable plastics synthesized through fermentation of natural high polymer and microorganism, which is being researched and developed in home and abroad. As for the high-starch content biological degradable plastics or high inorganic photo-oxygen degradable plastics developed in China at present, besides their good environmental benefit, what is important about them lies in the application of renewable resources or resources with large reserves and rich sources to replenish and substitute petroleum and chemicals, such as polyethylene (PE) and polypropylene (PP) plastic film/bag and containers with 30% - 60% starch content. This means that 1 ton of the above products may substitute 300 – 600 kg PE and PP, and makes them used more efficiently in more demanding field. As a result, the sources of raw materials are expanded and the basis of resources is strengthened, and the service life of fossil fuel reserve is lengthened. Thus the economy has laid a basis to develop towards to the sustainable development in an orderly manner.

5.    LCA

It can be seen in above analysis that environmentally degradable plastics play an important role in environmental protection and sustainable development. Besides, Japan Biodegradable Plastics Research Association recently made LCA comparison analysis (see Table 1) on raw materials and resource recycle of ordinary plastics and biodegradable plastics. It is fully proved by the data listed in the table that biodegradable plastics are a kind of low environmental load material. The high-starch content biodegradable plastics and high calcium carbonate photo-oxygen degradable plastics researched and developed in China at present are between ordinary plastics and all biodegradable plastics in the effect of their energy consumption and resource recycle on nature. It is also proved based on this analysis that environmentally degradable plastics may reduce pollution, save resources, have better environmental benefit and is in conformity with the trend of sustainable development.

Table 1  LCA Analysis of Ordinary Plastics and Biodegradable Plastics ^[5]

References:

[1]   Environmental Protection and Sustainable Development      Qian Yi, 2002, 132-153

[2]   China Chemical Information Weekly      2002, (26): 11

[3]   China Chemical Information Weekly       Zhu Cenghui, 2001, (15): 14

[4]   China Chemical Information Weekly       Zhu Cenghui, 2001, (16/17): 15

[5]   Plastics   Ojima-ichishi, 2001, 52 (10): 10

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