◎Reporter Li He
my country's degradable plastics industry has undergone many technological innovations, from photodegradable plastics to starch-added degradable plastics to fully degradable biodegradable plastics.
Data show that the average annual growth rate of my country's biodegradable plastic consumption in the past five years was about 20%. In 2019, my country's biodegradable plastic consumption was about 260,000 tons.
"Double 11" has passed and "Double 12" is coming soon. Behind the "buy, buy, buy" and massive express parcels, there is a continuous increase in plastic packaging waste, which brings tremendous pressure on ecological and environmental protection.
With the implementation of "plastic ban" and "plastic restriction" in various places, the promotion of the use of degradable materials, especially biodegradable plastics, in express delivery and daily life is an effective way to reduce environmental pollution.
What is biodegradable plastic?
What are the challenges facing the promotion and popularization of biodegradable plastics?
A reporter from Science and Technology Daily interviewed relevant experts on these issues.
It’s not just “biological”, but it depends on microbial degradation
Biodegradable plastics, also known as biodegradable plastics, biodegradable plastics, can be completely degraded in nature, or under certain conditions such as composting, anaerobic or aqueous culture solutions, relying on the action of microorganisms such as bacteria, molds, and algae. Carbon dioxide, methane, water, etc.
For biodegradable plastics, the word "biological" means that it needs to be degraded by microorganisms, and does not mean that it must be produced with biological materials.
Professor Du Huanzheng, director of the Institute of Ecological Civilization and Circular Economy of Tongji University, explained that biodegradable plastics can be produced from petroleum or bio-based materials.
For example, polylactic acid (PLA) is currently the most mature, most productive, and most widely used biodegradable plastic in the world.
PLA is a polymer polymerized from lactic acid as the main raw material. It can be produced from starch or petroleum.
"According to the raw material source of biodegradable plastics, it can be divided into two types: bio-based biodegradable plastics and petrochemical-based biodegradable plastics." Diao Xiaoqian, deputy secretary general of the Degradable Plastics Professional Committee of China Plastics Processing Industry Association, said that petrochemical-based biodegradable plastics are Refers to biodegradable plastics made by polymerizing petrochemical products by chemical synthesis, such as polybutylene terephthalate (PBAT), polybutylene succinate (PBS), Carbon dioxide copolymer (PPC).
The source of raw materials for bio-based biodegradable plastics is very wide.
According to the source, it can be divided into four categories: The first category is plastics directly processed from natural materials. Natural material sources include plant and animal sources. Plant sources include cellulose and lignin, and animal sources include gelatin, chitin, Chitosan, etc.; the second category is a polymer produced by microbial fermentation and chemical synthesis; the third category is a polymer directly synthesized by microorganisms; the fourth category is a blend of these materials, or these materials and Other chemically synthesized biodegradable plastics are blended and processed.
The biodegradable plastics industry has experienced many technological innovations
In Haikou, Sanya and other places, reporters found that whether shopping in supermarkets or drinking milk tea, coffee, etc., the shopping bags and straws used are made of biodegradable plastic.
From December 1, 2020, Hainan has officially banned the use of disposable non-degradable plastic products.
However, when consumers get biodegradable plastic products, they may not expect that the biodegradable plastic industry has undergone many technological innovations, many trials and errors, and corrections.
"Photodegradable plastics" is the beginning of my country's biodegradable plastics industry.
In the early 1970s, plastic film technology entered my country and was applied in the agricultural field to increase crop yields.
However, as more and more plastic films accumulate in the soil, problems such as "white pollution" have been brought.
Based on this, photodegradable plastics came into being.
The photodegradable plastic olefin polymer can change from a large molecule to a small molecule segment after being irradiated with light, but this is only a "disintegration" and cannot fundamentally degrade the polymer into a substance that is harmless to the environment.
The small fragments produced by the disintegration still remain in the soil and cannot be recycled, which affects the growth of plant roots, and may even enter the human body through the food chain, endangering human health.
The road to "photodegradation" was not feasible, so by the 1990s, degradable plastics entered the stage of starch-added degradable plastics, and product research and development mainly focused on the direction of "filled starch plastics".
Filled starch plastics mainly use starch as a filler to fill polyethylene (PE), polypropylene (PP), etc., usually with a filling amount of 10%-30%.
"Filled starch plastics essentially still contain polyolefin polymers such as PE and polystyrene (PS), which can only be partially degraded and still pose environmental hazards." Du Huanzheng said that now, degradable plastics have reached the stage of fully degradable plastics.
Fully degradable plastics include PLA, PBAT, polyhydroxy fatty acid esters (PHA) and other natural polymer materials such as biodegradable plastics.
Most of them have the advantages of fully biodegradable, good mechanical properties and processability.
Data shows that the average annual growth rate of my country's biodegradable plastic consumption in the past five years has been around 20%. In 2019, the domestic consumption of biodegradable plastics was about 260,000 tons.
With the intensive introduction and gradual implementation of plastic bans and restrictions, the key alternative areas are disposable films, express packaging, online takeaways, etc.
It is estimated that by 2025, the above-mentioned areas are expected to achieve substantial substitution of biodegradable plastics. The conservatively estimated demand is about 6.93 million tons, and by 2030, it will require about 13.86 million tons.
The bottleneck of the development of biodegradable plastics is gradually breaking
Biodegradable plastics can replace traditional plastics in areas such as disposable films and express packaging, and can also be used in fields such as agricultural mulch, textile fibers, durable plastic tableware, automotive industrial products, foam products, and 3D printing materials.
However, the Prospective Industry Research Institute pointed out in the article "The Atlas of Degradable Plastics Industry: Overview, Development History, Production Process Trends and Bottlenecks" that the development of biodegradable plastics still faces multiple challenges.
For example, the current price of biodegradable plastic bags on the market is more than three times that of traditional plastic bags. If there are no mandatory regulations, it is difficult to promote in the market; there is a lack of mandatory standards, especially the standards for biodegradable plastics vary from place to place. Qi, leading to difficulties in the supervision of government regulatory agencies.
However, the bottleneck of the development of biodegradable plastics is gradually breaking through.
In the short term, as the production capacity of biodegradable plastics is gradually released, price growth will gradually slow down.
In the long run, with the diversification of raw materials and technological progress, the overall price of biodegradable plastic products will decline.
In addition, my country is promoting the development of standards for biodegradable plastics.
The Ministry of Industry and Information Technology stated that in the next step, it will continue to support the formulation and revision of national standards in the field of biodegradable plastics such as "Biodegradable Materials and Products Degradability and Labeling Requirements", "Full Biodegradable Drinking Straws" and other national standards in the field of biodegradable plastics. Provide technical support for the promotion of plastic pollution control.
Du Huanzheng said that to solve the problem of plastic pollution, the first is to reduce the use of plastics, and then to increase recycling and then to replace them.
Substitutions include replacement of paper, replacement of other materials, and replacement of non-degradable plastics with degradable plastics.
In this context, the biodegradable plastic industry may develop more rapidly.