By Wang Xiaolong, Beijing University of Chemical Technology
In recent years, the introduction of relevant national regulations and policies and people’s rising environmental awareness has brought about new opportunities for the biodegradable plastics industry development. The preparation, research and technologies of biodegradable plastics represented by polylactic acid (PLA) and polybutylene adipate (PBAT) have continuously made breakthroughs and improvements. Although marketing is faced with some difficulties due to restrictions such as price factors, the growth potential is tremendous and demand will see rapid increases in the following years. Biodegradable plastics is poised to become the main force of the plastics industry.
Traditional plastics in transition to biodegradable plastics
With the deepening understanding of the harm that plastic wastes cause to the environment, countries around the world have made reducing the use of plastic as an important task of environmental protection and are curtailing the use of plastic products through the implementation of various policies and regulations. The European Union clearly stated that it will levy a "plastic packaging tax" effective from January 1, 2021. China's "plastic ban" has lasted nearly 20 years. In January 2020, China’s National Development and Reform Commission (NDRC) and the Ministry of Energy and Environment issued the Opinions on Further Strengthening the Treatment of Plastic Pollution. Since September 2020, China’s newly revised "Law on the Prevention and Control of Environmental Pollution Caused by Solid Wastes" was officially implemented, setting a clear timetable for prohibiting and restricting the production of non-degradable plastic bags and other disposable plastic products.
The “plastic ban” is a great boost to the development of new biodegradable plastics. Biodegradable plastic is a kind of polymer material with excellent performance. It can be completely decomposed by environmental microorganisms after being discarded, and finally inorganicized to become a component of the carbon cycle in nature. Driven by environmental protection policies, PLA, PBAT, polybutylene adipate (PBSA), polybutylene succinate (PBS), polyhydroxyalkanoate (PHA), Polyε-caprolactone (PCL), and related starch-based thermoplastic composite materials and other biodegradable plastics, are used in disposable tableware, packaging, agriculture, automotive, medical and textile applications, and are ushering in new opportunities for development. Figure 1 is the market distribution of China’s biodegradable plastics in 2019. By 2025, China’s demand for biodegradable plastics is expected to reach 2 380 kt, with market size at RMB47.7 billion and by 2030, the demand will rise to 4 280 kt and market size at RMB85.5 billion. China’s biodegradable plastics market has a huge growth potential.
Figure 1 China’s biodegradable plastics market distribution in 2019
PLA: improving technologies, large-scale promotion and application around the corner
PLA is a biodegradable polymer synthesized by polymerization of plant resources. It has sufficient and renewable raw material source and can be recycled after use. As an ideal green and environmentally friendly polymer material, PLA has become the main product in the biodegradable plastic series.
Zhejiang Haizheng Biomaterials started up its first 5 kt/a PLA production line in late 2005 and has so far expanded its capacity to 25 kt/a. Another 50 kt/a PLA unit is under construction. Shenzhen Esun Industrial has established an annual production capacity of 10 kt/a of polymers, 15 kt/a of lactate, 5 kt/a of polyols, and 1 500 t/a of 3D printing materials and produces film, injection, sheet and fiber grades PLA products. Jilin COFCO Biotechnology has 30 kt/a PLA and 30 kt/a bio-based products capacity. In August 2020, Anhui Fengyuan Futailai successfully achieved PLA granules. In September, its first module project with an annual output of 500 kt of lactic acid and 300 kt of PLA was put into construction. A large number of biodegradable PLA projects are entering the construction climax, including Shandong Hongda Biotechnology Company’s 160 kt/a PLA project, Zhejiang Youcheng Holding Group’s 160 kt/a PLA project, Shandong Tongbang New Materials Technology’s 300 kt/a lactic acid, 200 kt/a PLA and 100 kt/a PLA fibre project, Zhejiang Youcheng Holding Group’s 750 kt/a lactic acid and 500 kt/a PLA project using bagasse as raw material and Jindan Biological New Materials Company’s 10 kt/a PLA project.
At present, the primary problem that plagues the development of China's PLA industry is the manufacturing technology of PLA synthetic intermediate lactide, which encounters problems such as high energy consumption, high cost, and insufficient yield and purity. While imported lactide is highly priced, with limited supply, which hinders PLA capacity expansion and further boosts the PLA prices. Currently, sales prices of PLA stand at RMB27 000-35 000/t. Therefore, to vigorously promote the various applications of PLA, it is necessary to develop downstream application manufacturing technology. For example, by blending with other biodegradable materials such as starches, cellulose, PBAT, PHA, PBS, etc. In addition, through the development of lightweight processing technology for PLA products, the quality of PLA used in products is reduced, so as to cut manufacturing costs. With the continuous improvement of PLA production and subsequent modification technology, the large-scale popularization and application of PLA resin in China is just around the corner.
PBAT: projects in construction and planned to cover capacity gap
PBAT displays good tensile strength, toughness, ductility and heat resistance, and its mechanical properties are better than PLA. It is very active in the research of biodegradable plastics and one of the best degradable materials applied in the market. It is mainly used in fully degradable packaging films and fully degradable packaging bags (shopping bags, garbage bags in rolls, electronic product packaging bags, food packaging bags, mulch, etc.).
Xinjiang Lanshan Tunhe Degradable Materials has 120 kt/a PBAT capacity. Jinfa Technology’s subsidiary Zhuhai Wantong Chemical’s PBAT industrial synthetic unit realised 60 kt/a of capacity. The PBAT production technology, developed by Sinopec Yizheng Chemical Fiber further promoted the industrialization of domestic biodegradable materials. There are around 384 kt/a of PBAT capacity already launched production in China. The integration of upstream PBAT products, fewer technical barriers and far lower investment and construction costs than PLA resin motivated many companies to build up PBAT plants. Table 1 shows PBAT projects under construction and in planning phases in China. Upon the release of these new capacities, China’s supply gap of PBAT will be covered, and therefore dragging down domestic PBAT prices.
At present, FMCG packaging and agricultural film are still the main markets of PBAT. Given that PBAT has mechanical properties and heat resistance similar to aromatic polyester materials, demand for PBAT will grow rapidly, with the development of new application fields for environmentally friendly materials in the automotive and electronic industries.
Other biodegradable plastics emerged
PBS is a kind of polyester among the biodegradable plastics. It uses aliphatic succinic acid and butanediol as the main production materials and is synthesized by direct esterification or transesterification. PBS derivatives, PBAT and PBSA have emerged given the limited supply of feedstock succinic acid. Figure 2 shows the comparison of physical and chemical properties of PBS, PBAT and PLA. PBS boasts excellent processing performance. Almost all molding processing methods (blow molding, injection molding, extrusion molding, sheet molding, foam molding, vacuum molding, etc.) used in current resin materials can be applied to the processing of PBS. At present, PBS is mainly used in degradable garbage bags, packaging bags, cosmetic bottles, various plastic cards, baby diapers, agricultural materials, and drug slow-release carrier substrates.
Figure 2 Physical and chemical properties of PBS, PBAT and PLA
China’s PBS industry started relatively late but has been developing rapidly. In 2006, Anqing Hexing Chemical and Tsinghua University cooperated to build a 3 kt/a PBS production line, which has reached 10 kt/a of capacity. Shandong Landian Technology Holding uses biological fermentation to produce bio-based succinic acid, which is used as a raw material for PBS production and has formed 200 kt/a of capacity. The first phase of Xinjiang Lanshan Tunhe Chemical’s one-million-ton biological new material technology industrial park held a groundbreaking ceremony in Changji National High-tech Development Zone. The industrial park plans to fully complete by the end of the "14th Five-Year Plan" period the 400 kt/a PBS and other polyester projects. Lanshan Tunhe currently has 120 kt/a PBS capacity. Jinfa Technology is producing a few PBS products. Yingkou Kanghui Petrochemical’s 33 kt/a PBS project is under construction and is expected to start up at the end of 2020. Jinhui Zhaolong’s PBS project is in the final trial run phase. Inner Mongolia Dongyuan Technology is establishing a 200 kt/a PBS biodegradable polyester project in Wuda Industrial Park of Wuhai Economic and Development Zone.
PHA is the general term for polyhydroxyalkanoate biodegradable plastics. Poly-3-hydroxybutyrate (PHB), polyhydroxyvalerate (PHV), and a copolymer of PHB and PHV (PHBV) are the most common. PHA can be used in the disposable products, medical equipment surgical gowns, packaging bags and compost bags, medical sutures, repair devices, bandages, orthopedic needles, anti-adhesion membranes and stents. Compared with PLA and PBAT, the degradation conditions of PHA are the mildest. But its market share is only 2% as the large-scale industrialization and commercialization of PHA is restricted by high production costs. Currently, PHA is mainly used in high value-added sectors, such as medical equipment. With the further reduction of costs and the development of high value-added applications, PHA will become a biomaterial with a cost acceptable to multiple applications.
Other biodegradable plastics, including carbon dioxide copolymer (PPC), polyacyl ester copolymer (CPAE), polyvinyl alcohol and polyethylene glycol, PCL and a large number of new biodegradable plastics are also in the stage of in-depth research, development and industrialization.
Restricted promotion, industrial process to speed up in an all-around way
Despite the rapid development of biodegradable plastics, the promotion of the materials meets with difficulties. This is mainly due to the following reasons: First, the performance of degradable plastics needs to be improved, especially for the low load-bearing capacity of plastic bags used for fast-moving packaging; second, the color of degradable plastics is dim and yellow, with low transparency; third, high prices; fourth, lack of strong policy or legal and regulatory support, which is not conducive to the development of production-oriented enterprises; fifth, the return cycle of the biodegradable plastics industry is longer than expected, resulting in insufficient corporate funds and difficult financing; sixth, the evaluation system is not perfect, and many materials and products do not have product standards, which brings many inconveniences and disputes to trade.
To solve the existing problems, it is necessary to strengthen the research and development level of biodegradable plastics, especially the level of independent intellectual property rights in the development of bio-fermentation strains; while vigorously developing new biodegradable plastics, based on existing degradable plastic varieties, strengthen the development of biodegradable plastic modification technology, and at the same time strengthen the development of related additives to reduce their use costs; for some special non-recyclable medical plastic products, garbage bags, compost bags, pesticide bottles and cosmetic containers and other disposable plastic products application fields, it is necessary to vigorously develop high-quality, low-price polymer composite materials based on bio-based fillers such as cellulose, starch and chitin to replace biodegradable plastics. In addition, to offer policy and subsidy supports to the application and development of biodegradable plastic products; to strengthen investment in biodegradable plastic standards, testing technology, etc., and improve product standards.
Demand for biodegradable plastics will brace for medium-to-high growth in the coming years, with the production technology and application fields constantly making breakthroughs and production costs and prices moving downwards.
