From the comprehensive upgrade of the plastic restriction order, to the complete ban on the use of disposable non-biodegradable plastics in commercial stores, catering industries, and food delivery services, biodegradable plastics are rapidly entering our daily lives and have become the core solution to replace traditional petroleum-based plastics. Plastic bags, food containers, courier packaging, agricultural mulch films - these once seriously polluting plastic products now have degradable alternatives. They are also regarded by many as the ultimate solution to ending white pollution. However, at the same time, controversies about degradable plastics such as "false degradation, real pollution", "demanding degradation conditions", and "higher carbon emissions" have never ceased. Many people are curious: What exactly is biodegradable plastic? What are its essential differences from traditional plastics? Can it really completely degrade in the natural environment? Can it completely solve the problem of white pollution? What is its development prospect?
Traditional plastics are high-molecular polymers synthesized from fossil energy sources such as petroleum and coal. Examples include polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), and polystyrene (PS). Their molecular structures are extremely stable and take hundreds or even thousands of years to be completely decomposed in the natural environment. During the decomposition process, microplastics are produced, which seep into the soil, water bodies, and even enter the food chain, causing long-term harm to the ecological environment and human health. According to statistics, the global annual production of plastics exceeds 400 million tons, of which more than half are disposable plastic products. Less than 10% are recycled, and the vast majority are buried, incinerated, or released into the natural environment. White pollution has become a global ecological problem.
Biodegradable plastics were developed precisely to address the problem of the non-degradability of traditional plastics. They are high-molecular materials synthesized from renewable biomass resources or a small amount of petroleum-based raw materials. Under specific environmental conditions, they can be completely decomposed by microorganisms in nature, such as bacteria, fungi, and algae, into harmless substances like carbon dioxide, water, and biomass, without leaving any plastic residues or microplastics, thus fundamentally solving the environmental pollution problem caused by plastics. However, many people have noticed that the biodegradable plastic bags they bought still show no obvious signs of degradation after being placed in the natural environment for several months. This is not a problem with the biodegradable plastics themselves, but rather because the degradation of biodegradable plastics requires specific environmental conditions. Different types of biodegradable plastics have significant differences in the environmental conditions, cycles, and mechanisms of degradation.
The mainstream biodegradable plastics currently available on the market are mainly divided into four categories based on their raw material sources and synthesis methods. Each category has its own unique performance characteristics and applicable scenarios. The first category is polylactic acid, also known as PLA, which is the most common biodegradable plastic. It is synthesized from lactic acid produced through fermentation of biomass materials such as corn, cassava, and straw. The raw materials are fully renewable, and the production process has extremely low carbon emissions. Its mechanical properties and transparency are similar to traditional PET plastic, and it can be used for making plastic bags, food containers, disposable tableware, packaging materials, 3D printing materials, etc. The second category is polybutylene adipate/trimethylene terephthalate, also known as PBAT. It is a petroleum-based biodegradable plastic with excellent flexibility and extensibility, good impact resistance and puncture resistance, similar to traditional polyethylene plastic in performance, but it can completely degrade in a compost environment. It is usually mixed and modified with PLA to compensate for PLA's poor toughness and poor flexibility. The biodegradable plastic bags and cling films we commonly use are mostly blends of PLA and PBAT. The third category is polyhydroxyalkanoates, also known as PHA. It is a natural polymer polyester synthesized by microorganisms through fermentation. It is completely synthesized by microorganisms and can be degraded in industrial compost environments, as well as in natural environments such as seawater, soil, and fresh water, and even in the human body. It is the only biodegradable plastic that can rapidly and completely degrade in the ocean environment, and has great application potential in marine environmental protection and medical materials. The fourth category is starch-based biodegradable plastics, which are made from corn starch, potato starch, and other raw materials and are blended and modified with other biodegradable polymers. The raw materials have low cost and are renewable, and they can be fully biodegraded. However, they have poor water resistance and low mechanical strength, and are mostly used for making disposable packaging and cushioning materials.
The misunderstandings about degradable plastics come from the confusion between "degradable" and "degradable anywhere". The majority of degradable plastics, such as PLA and PBAT, need to be in an industrial composting environment, which is a constant temperature of around 58℃, constant humidity, sufficient oxygen and specific microbial communities, to completely degrade into carbon dioxide and water within 180 days. In a normal temperature natural environment, such as indoors at home, outdoor soil, or in the ocean, their degradation rate becomes extremely slow, and it may take several years for them to completely degrade, which is not much different from traditional plastics. PHA materials, although they can degrade in natural environments such as seawater and soil, have high production costs and a small production scale. Currently, they cannot be widely popularized for civilian use. This is the core reason why many people think degradable plastics "do not degrade", not because the materials themselves do not have the ability to degrade, but because they do not enter the corresponding degradation environment and do not have a corresponding industrial composting system. In the end, degradable plastics still end up in landfills and incineration plants along with traditional plastics, and cannot fulfill their environmental protection value.
Apart from the issue of degradation conditions, the development of degradable plastics also faces many controversies and challenges. Firstly, there is the cost issue. Currently, the mainstream degradable plastics such as PLA and PBAT have a production cost that is 2-3 times that of traditional polyethylene and polypropylene plastics. This leads to the prices of degradable plastic products being much higher than those of traditional plastic products, which hinders their large-scale popularization and application. Secondly, there are disputes over raw materials and food security. Currently, the main raw material for PLA is food crops such as corn and cassava. Many people are worried that large-scale production of degradable plastics will compete with humans for food, affecting food security. However, the industry is currently developing non-food raw material production technologies for PLA, using agricultural waste such as straw and corn husks as raw materials, through biological fermentation to produce lactic acid, no longer consuming food resources, and solving this problem at its root. Thirdly, the recycling system is not perfect. The recycling systems for degradable plastics and traditional plastics are incompatible. If degradable plastics are mixed into the recycling process of traditional plastics, it will affect the performance of recycled plastics, leading to a decline in the quality of recycled materials, and specialized recycling and composting systems for degradable plastics in China are still in the initial stage. Many cities do not have corresponding industrial composting facilities, making it impossible for degradable plastics to achieve true closed-loop degradation. Fourthly, there are problems with industry standards and market chaos. Currently, many plastic products labeled as "degradable" on the market are actually just adding a small amount of degradable components to traditional plastics, or adding fillers such as starch and calcium carbonate. They cannot achieve complete degradation and instead accelerate the fragmentation of plastics, generating more microplastics, causing more serious pollution. This requires further improvement of industry standards and strengthening of market supervision to prevent fake degradable products from entering the market.
Despite numerous challenges, biodegradable plastics remain the core direction for addressing white pollution and promoting the green and low-carbon transformation of the plastic industry. It is also an important path towards achieving the dual carbon goals. The production of traditional plastics is entirely dependent on fossil energy. The annual carbon emissions of the global plastic industry exceed 1.5 billion tons. However, the raw materials for biodegradable plastics mostly come from renewable biomass. The carbon emissions during the production process of biodegradable plastics are much lower than those of traditional plastics. Moreover, after degradation, the carbon dioxide produced will be reabsorbed by plants through photosynthesis, forming a complete carbon cycle, with almost no additional carbon emissions. It is truly a green and low-carbon material.
In the field of biodegradable plastics, our country has already taken the lead globally. It is the world's largest producer and consumer of biodegradable plastics. Domestic enterprises have broken through the production technologies of core materials such as PLA, PBAT, and PHA, achieving large-scale production. The production capacity ranks first globally. From raw material production, modification processing to product application, a complete industrial chain has been formed. At the same time, China's PLA production technology from non-food raw materials and the technology for converting straw into lactic acid have reached international advanced levels, completely摆脱ed the reliance on food raw materials. With the full implementation of the plastic restriction order， the domestic biodegradable plastic market is growing rapidly. Its application scenarios have gradually expanded from one-time packaging and tableware to agricultural mulching films， medical consumables， 3D printing， automotive interiors and other fields.
More importantly, the supporting system for degradable plastics in our country is constantly being improved. Industrial composting facilities, the recycling and disposal system for biodegradable plastics, are gradually being established. Relevant national standards and industry norms are also being continuously refined. Market supervision is continuously strengthened, and the chaos of fake degradable products is being rectified. At the same time, with the continuous advancement of technology and large-scale development, the production cost of degradable plastics is continuously decreasing. In the future, it is expected to achieve cost parity with traditional plastics, laying the foundation for large-scale popularization and application.
From non-biodegradable petroleum-based plastics to fully biodegradable green plastics, the plastic industry is undergoing a brand-new green revolution. Biodegradable plastics are not the only solution to end white pollution, nor are they a universal solution. They need to be combined with measures such as reducing plastic use, recycling, and circular utilization to form a complete governance system of "source reduction - recycling - end degradation". In the future, as technology continues to mature and the supporting system is continuously improved, biodegradable plastics will surely achieve larger-scale application and gradually replace traditional disposable plastics, allowing us to completely get rid of the trouble of white pollution and protect our ecological environment.
