Plastic products have brought great convenience to people's life. However, after a large number of plastic products are used and discarded, the environmental problems caused by improper disposal have become a global concern. Of the 120 million tonnes of single-use plastic produced globally each year, only 10 per cent is recycled, another 12 per cent is incinerated and more than 70 per cent is thrown away into the soil, air and oceans.

Biodegradable plastic refers to a kind of plastic whose properties meet the requirements of use during storage period, and can be decomposed into environmentally harmless substances in natural environmental conditions after use. It is considered as one of the effective ways to solve the problem of plastic pollution, and has attracted attention in recent years.

Chinese biodegradable plastics are still in the early stage of industrialization. At present, there are many kinds of biodegradable plastic products on the market, and there are great differences in product performance and production capacity scale. In order to promote the understanding and understanding of Chinese biodegradable plastics industry, this paper combs and analyzes the product classification and market situation, the performance comparison of typical biodegradable plastics and other aspects, in order to provide reference for the relevant industry personnel.

1. Industrial development policy background

The problem of disposable non-degradable plastic pollution has attracted global attention, and countries around the world have introduced relevant policies to control it. Since 2020, the National Development and Reform Commission, the Ministry of Ecology and Environment and other ministries and commissions have issued several policy documents on plastic pollution control, including Opinions on Further Strengthening Plastic Pollution Control and Notice on Steadily Advancing Plastic Pollution Control, which have put forward a clear timetable for banning or limiting single-use non-degradable plastics.

"From 2020 to the end of 2025, the use of non-biodegradable plastic bags should be phased out nationwide, the consumption intensity of non-biodegradable disposable plastic cutlery in food and beverage takeaways in cities at and above the prefecture level should be reduced by 30%, and plastic pollution nationwide should be effectively controlled by 2025", and local people's governments at all levels should be combined with local conditions. We will formulate specific measures for their implementation and refine policies and measures.

At present, all regions are striving to promote the implementation of the "New Policy to limit plastic". Most provinces such as Hainan, Hebei, Guangdong, Shandong, Henan, Zhejiang and Tianjin have issued implementation plans for plastic pollution control, all of which list degradable plastic products as alternative products that can be promoted and applied.

Under the strong drive of policies, the future market demand for degradable plastics may see a large growth, especially the express packaging, take-out, hotel and other industries have strong demand for disposable degradable plastic products, and degradable plastics usher in new development opportunities.

2. Classification and market situation of degradable plastics

2.1 Classification and Usage

Currently, biodegradable plastics can be divided into two categories, biological and petrochemical based, according to the source of raw materials. Biodegradable plastics include polylactic acid (PLA), polyhydroxyfatty acid ester polymers (PHAs), whole starch base, cellulose, etc. Petrochemical based degradable plastics include dibasic acid diol copolyesters (polybutylene succinate (PBS), polyadipate/butylene terephthalate (PBAT), carbon dioxide copolymer (PPC), polycaprolactone (PCL), polyglycolic acid (PGA), etc.

Among them, the biodegradable starch based plastics belong to the first generation of degradable plastics, because they can not achieve complete degradation of plastics, there is a trend of gradual elimination. At present, the industrial scale production is formed in the Chinese market, and the main ones that occupy a larger market share are PBAT, PBS, PLA, etc.

From the specific use of various degradable plastics, PBAT/PBS series products are mainly used in packaging, tableware, cosmetics bottles and medicine bottles, disposable medical supplies, agricultural film, pesticide and fertilizer slow-release materials.

PCL is used in the production and processing of shaping materials, toys, shell sutures, bone nails, long-acting drug control and release carrier and other medical fields; PLA is used in general plastics such as film, lunch boxes and other disposable products, textile, 3D printing, biomedical and other fields. PPC is used in film bag products, plastic film, express packaging, paper and plastic composite product application, injection molding, blister, extrusion products, environmental adhesive and other fields.

PGA is used in oil and gas mining (bridge plug, fracturing ball, etc.), surgical sutures, bone nails and other medical fields, as well as membrane, packaging materials, disposable products and other fields. Although the application fields of different materials overlap to a certain extent, they have their own characteristics and focuses. In the actual use process, they are often copolymerized or blended in different proportions according to the specific needs of applications.

2.2 Supply and demand

2.2.1 Availability

Global degradable plastics are in the early stage of industrialization, and China's production capacity has increased significantly. In 2019, the production capacity of mainstream biodegradable plastics in China was about 370,000 tons, and the output was about 260,000 tons. The PLA has a capacity of about 130,000 tons/year. Due to technical reasons or lack of lactide, some PLA units cannot operate stably or are shut down. The actual effective capacity is about 48,000 tons/year, and the output is about 18,000 tons/year.

The main production enterprises are Zhejiang Haizheng Biological, Anhui Fengyuan Group, etc. The PLA project under construction has a production capacity of about 80,000 tons/year, and the long-term planned production capacity is about 1.2 million tons/year. The production capacity of PBS/PBAT is about 240,000 tons/year. As the production technology of petrochemical base products is relatively mature, it can basically achieve full load operation, and the output is basically consistent with the production capacity, about 240,000 tons.

Large domestic PBS/PBAT production enterprises include Jinfa Technology, Xinjiang Lanshan Tunhe, etc. The combined capacity of PBS/PBAT class under construction is about 687,000 tons/year, and the long-term planned capacity is about 1.5 million tons/year. Since 2020, there have also been coal-based PGA products entering the market in China, which have attracted great attention from everyone.

2.2.2 Requirements

In recent years, with the gradual implementation of the domestic plastic ban policy, the market demand for degradable plastics has been increasing. In the past five years, the average growth rate of the consumption of biodegradable plastics in China was about 20%. In 2019, the consumption of biodegradable plastics in China was about 260,000 tons, which was basically consistent with the output due to the restriction of the output.

At this rate of growth, China's demand for biodegradable plastics is expected to exceed 650,000 tons by 2024. Considering the intensive introduction of "plastic restriction" policies in China since 2019 and their gradual implementation, the growth rate of the market demand for degradable plastics will further increase, and it is expected to exceed 1 million tons in 2024.

3. Comparison of properties of typical degradable plastics

The author has made a comparative analysis of some properties of several typical degradable plastics which can basically achieve industrial scale production and have a certain market share at present. See Table 1 for details.

Table 1 Comparison of performance indexes between different degradable plastic products and typical polyethylene products

Generally speaking, all kinds of degradable plastics have their own characteristics, and the use range of the above materials without adequate modification is relatively limited. In the actual use process, the material properties should be fully combined with additives for blending in specific fields.

Specifically, PCL has good ductility, biocompatibility, memory, easy molding and processing, but low melting point, heat resistance is general; PLA has good heat resistance, stable performance and good luster at room temperature, but poor toughness and general gas barrier. PBS and PBAT have good mechanical properties and toughness, high processing properties and thermal stability, but low strength, luster is average. PGA has good biocompatibility, gas barrier, mechanical properties, high strength, fast degradation rate, good gas barrier, but low toughness.

4 Conclusion

Combined with the current policy of banning and restricting disposable non-degradable plastics and the promotion policy of degradable plastics, the demand for degradable plastics is relatively strong. From the perspective of domestic production capacity and output, it is still unable to meet all aspects of demand. The market of degradable plastics will maintain a high price in the short term, and the industry will maintain a high profit level.

Judging from the existing characteristics of several degradable plastics in the market, it is unlikely to form an all-round competition in the short term. As the modification technology of degradable plastic products is gradually mature, the competition will be intensified. In the long run, the development of degradable plastics industry is still uncertain.

First, policy risks. Currently, the degradable plastics market is expected to mainly rely on macro-policies to promote, but there are no supporting subsidy policies and detailed regulatory measures for the degradable plastics industry. The sustainability of relevant policy costs remains to be seen.

At present, the cost of degradable plastics is still much higher than that of traditional PP and PE, and in many low-end application fields (such as agricultural mulch products), consumers are highly sensitive to the price of products, and the promotion and application prospects of products ultimately depend on the space of industrial cost reduction and efficiency improvement. In the future, it may be difficult to sustain the industrial development due to the unrecognition of consumers and slow technological progress.

Third, the effect risk. At present, the degradability of many degradable plastics is based on the effect measurement under the condition of centralized treatment of industrial compost. However, there is still a risk whether they can meet the above degradation requirements after actual use. However, the degradation effect in a completely natural environment still needs to be verified, which also concerns whether the original intention of industrial development can be achieved.

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