China's "most stringent plastic restriction order in history" has been implemented for nearly two years. The opinions on further strengthening plastic pollution control (hereinafter referred to as the plastic restriction order) issued in January 2020 prohibits or restricts the production and sales of disposable plastic shopping bags, tableware and other products, and sets an ambitious exit timeline. For example, some disposable plastic products need to be completely withdrawn from the market in less than a year.
The rapid elimination of a large number of disposable non degradable plastic products has led to the rapid growth of the production capacity of substitutes in a short time. Among them, biodegradable plastics are particularly attractive. Weng Yunxuan, Professor of polymer chemistry at Beijing University of technology and technology, predicts that by 2025, the annual production capacity of China's two main biodegradable plastic varieties PBAT and PLA will increase from about 300000 tons and 100000 tons in 2020 to about 7 million tons and more than 1 million tons, reaching more than two-thirds of the global production capacity.
However, a few months ago, in the action plan for plastic pollution control in the 14th five year plan issued by the national development and Reform Commission and the Ministry of ecological environment, the length of biodegradable plastics was significantly reduced, and there was no requirement to promote such products in the policy. Instead, it stressed the need to study the impact of degradable plastics, standardize the application fields, and clearly put forward to prevent blind expansion of production capacity.
What caused Chinese policy makers to change their attitude towards biodegradable plastics in a short time?
Unclear definitions and standards
One of the basic ideas for controlling disposable plastic pollution is to replace disposable plastic products with more environmentally friendly materials, and focus on the three performance directions of "recyclable, recyclable and degradable". Therefore, degradable plastic bags and degradable mulching films are considered by the industry as alternative products promoted by the state, so they are sought after.
But what exactly does the so-called "degradable plastic" mean? In China's current standards and guidelines, its definition and classification are not clear.
In the current national standard GB / t20197 definition, classification, marking and degradation performance requirements of degradable plastics published in 2006, degradable plastics are divided into four categories: biodegradable plastics, Compostable Plastics, photodegradable plastics and thermooxidative degradable plastics. The latter two categories are adding photosensitizers or catalysts on the basis of non degradable plastics, Break it into tiny plastic fragments - but these micro plastics may retain their original molecular properties, still cannot be absorbed by the environment, and will remain in nature because they are invisible to the naked eye, causing more serious pollution.
After the introduction of a series of national standards for thermal and biodegradable plastics in 2010, there was no longer a series of national standards for biodegradable plastics. These standards cover agricultural plastic film, shopping bags, express packaging bags, tableware and other major categories, but they are recommended standards and are not mandatory.
In 2020, the guidelines for the classification and identification of degradable plastic products formulated by China Light Industry Federation gave a new definition of degradable plastics, which clearly required that the biodegradation rate should be ≥ 90%. However, this guide does not have the binding force of national standards.
Unclear definitions and standards have led to market confusion. Wang Zhanjie, vice president and Secretary General of China Plastics Processing Industry Association, pointed out in an interview with China Newsweek that due to the lack of unified production supervision standards, the quality of degradable plastics products on the market is uneven. "There are some new types of degradable materials with technical disputes, which are known as degradable, but they can not finally meet the degradation standards".
At present, a new draft plan of "definition, classification, marking and degradation performance requirements of degradable plastics" has been released in November 2020, which is in the stage of soliciting opinions and has not yet been implemented. Once the standard comes into force, it will replace the old standard in 2006.
Is degradable plastic really degraded?
The confusion of standards is only one of the many problems with degradable plastics.
Like a seed, if it is thrown to a very cold place, it may never germinate; Degradable plastics can hardly be degraded if they do not meet the appropriate environment.
Even for the certified degradable plastics, the degradation reaction can only occur when certain conditions are met, and the degradation rate will be affected by oxygen, humidity, temperature, specific microorganisms and so on. Zhang Miao, director of Shanghai Pudong Yike recycling technology promotion center, told China foreign dialogue that, for example, PLA, one of the main degradable plastic varieties, needs to meet the temperature and humidity conditions of industrial compost to effectively degrade, and will not complete biodegradation in other low-temperature environments. For another example, PBAT, another large material, has extremely low degradation efficiency in water. Some experiments found that its degradation rate is less than 2% within 365 days of degradation, which means that it will bring harmful environmental impact in rivers, oceans and other water environments like non degradable plastics.
The latest report "Review on the application effect evaluation of degradable plastics" released by the center further pointed out that using existing biodegradable plastics to replace traditional plastics to solve the problem of marine plastic pollution "is likely to be wishful thinking".
Liu Hua, the project director of Greenpeace, believes that the results of the experimental environment can not be directly used as the basis for promoting degradable plastics. It is necessary to verify the degradation performance of degradable plastics in the actual use environment before they can be used in the corresponding environment. "Biodegradable plastics may actually pose the same risks to biological individuals, biodiversity and ecosystems as traditional plastics," Liu said. "So we need to demonstrate the suitability of degradable plastics in different scenarios to decide whether they should be promoted."
At present, biological disposal methods such as composting and anaerobic digestion can truly "degrade" degradable plastics. However, some experts pointed out at the "14th five year plan" plastic pollution control policy discussion Salon Hosted by Tianjin zero sprout public welfare development center that from the actual research, at present, the consumption and use of degradable plastics mainly occur in the field of life, and the vast majority of products in the field of life will eventually flow to incineration and landfill, which means that most degradable plastics cannot be optimized.
Degradable plastic management chain is difficult to form a closed loop
So, can strengthening the management of degradable plastic products after use ensure that these special plastics can enter the corresponding composting sites to realize degradation?
Theoretically, this is feasible, but due to the non-uniform standards of degradable plastics and high management and operating costs, this idea can hardly be implemented.
Liu Hua deduced step by step according to the management chain of Degradable Plastics: "Starting from household garbage classification, residents put it into kitchen waste bins, then transport it by classification, and finally enter the kitchen waste treatment plant for final treatment. No other non degradable or non certified degradable plastic bags can be mixed in any link, otherwise the kitchen waste treatment plant can only remove all garbage bags to ensure normal production requirements. However, if these plastic bags need to be removed in the end, then The conditions for the promotion of degradable plastic bags are not established. "
"Even if we assume that degradable plastic bags have certification marks, after being used, it is not in a clean and neat state, which can make it easy for you to identify. We can't guarantee that everyone who throws garbage can recognize degradable plastic bags, and we have no confidence that volunteers can supervise and ensure that every plastic bag entering the trash can is degradable." "In practical use, these degradable plastics will lose their due role if a relatively perfect closed-loop management is not formed," he said
In fact, at present, the comprehensive waste treatment plant does sort out the plastic bags mixed in kitchen waste as impurities, resulting in few biodegradable plastics entering the fermentation stage. An expert familiar with China's plastic waste treatment pointed out that impurity sorting equipment is generally included in kitchen waste biomass fermentation and treatment facilities, which aims to ensure that impurities such as plastic products cannot enter the fermentation link.
In addition, it is worth noting the economic cost of degradable plastics. According to Liu Hua's rough calculation based on the data released by the Beijing Municipal Urban Management Commission, assuming that each household in Beijing uses only one degradable plastic bag to contain garbage every day, the cost of purchasing degradable plastic garbage bags in Beijing will exceed 1.2 billion yuan throughout the year. However, according to the current waste treatment situation, the vast majority of disposable plastic bags have to be incinerated and landfilled. "With such a huge investment, but without the benefits claimed by degradable plastics, it is worth pondering whether promoting degradable plastics is still a reasonable choice," he said.
The aforementioned unnamed experts also believe that if degradable plastics are widely used in the field of life and ensure that these degradable plastics enter the kitchen waste treatment facilities for "degradation", a separate collection and transportation system must be established, which is too expensive. "In fact, the proportion of plastic waste in the field of life that can leak into the environment is not high. Instead, it is better to organize a normalized collection and salvage system. There is no need to use degradable plastics in the field that can be collected, and just use traditional plastics directly." "My view is that it is better to invest a relatively small cost in degradable plastics, which can be used in areas that directly cause environmental leakage, such as agricultural mulching films that are difficult to recycle," he said
According to Xinhua news agency, millions of tons of plastic film are used in China's agriculture every year, most of which are reduced to white pollution in the environment because they are difficult to recycle. The above review on the application effect evaluation of degradable plastics points out that the production of agricultural plastic film may be the most reasonable application direction of degradable plastics.
The debate and controversy surrounding biodegradable plastics have cooled the attitude of Chinese policymakers towards it. Perhaps just like the performance characteristics of this material itself, it needs harsh conditions and appropriate fields to make degradable plastics play a role in China's plastic pollution control strategy. While the boom of biodegradable plastics is fading, the action plan for plastic pollution control in the 14th five year plan also takes source reduction as one of the priorities. E-commerce, express packaging and procurement of organs and places will be the key areas of "plastic reduction" in the next five years.