The advantages of plastic are obvious: low cost of production, most plastics have high corrosion resistance, do not react with acids and alkalis, they are durable, waterproof, light and easy to process.
What we often refer to as white pollution is majority of plastic single-use consumer plastic products such as: single-use plastic bags, plastic straws, Styrofoam, etc. These plastic products are too expensive to recycle and remanufacture after disposal , so they basically do not recycle them, current treatment of these plastic wastes is incineration or landfill. Plastics burn easily and release toxic gases when burned. Due to their stable physical and chemical structure, plastics cannot be decomposed in natural environmental conditions by tens of -hundreds of years. It may take 200-400 years for plastic to be fully assimilated by microorganisms in soil, decomposed into CO2 and water to achieve inorganic mineralization, resulting in accumulation in environment.
However, nowadays, most plastic products such as sanitary trash cans, plastic pallets, plastic storage tanks, plastic water towers, cash boxes, plastic baskets, plastic barrels are recyclable. from low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE), and then high-density polyethylene (HDPE), polypropylene (PP) and other raw materials that can be recycled after culling. Skilled factories simply recycle and process, recover and use , which basically does not pollute environment.
Degradable plastics refer to substances that can be degraded into environmentally friendly substances under certain environmental conditions after use, and is a general term for a large class of degradable materials. Degradable plastics first appeared in 1960s and have gone through a developmental stage when mixed with traditional plastics, a degradation stage under photothermal conditions, and a degradation stage through microbial enzymatic reactions. Materials that mix degradable plastics with traditional plastics (such as polyethylene and polypropylene) can only make traditional plastics more prone to break into small fragments and produce more microplastics that pollute environment, so they cannot be considered degradable.
In fact, people often misunderstand that degradable plastic can decompose in any natural environment. In fact, degradable plastics only have degradable characteristics when placed in a certain environment, and they do not decompose under any environmental conditions.
The decomposition of degradable plastic can occur in conditions such as composting, burying in soil and fresh water. However, compared to soil environment, marine environment is characterized by high salinity and low microbial density. Those plastic products that can be degraded by microbial enzymatic reactions on land often decompose and break down in the marine environment.
Plastic storage tank
Research has shown that biodegradable plastics are currently mixed with other waste in incinerators and landfills. Compared to traditional plastics, not only do they have no environmental benefits, but they are also expensive, and overall profitability is extremely low.
In case of incineration, although degradable plastics have a biodegradable chemical structure, they are not much different from traditional plastic elements, and carbon emission effect and complex environmental impact after incineration are relatively close. In case of a landfill, biodegradable characteristics of degradable plastics make their carbon emissions higher than those of traditional plastics once they end up in landfills, and their overall environmental impact will be significantly higher than those of traditional plastics. For example, due to factors such as incineration and evacuation of landfill gas, direct release of methane from landfills, 1 kg of polylactic acid in landfills emits 3.1 kg of CO2 equivalent, which is about 35% more than CO2 equivalent of traditional plastic combustion.
The use of biodegradable plastic (bags) in everyday consumption and its disposal in kitchen waste treatment plants is being actively promoted by many businesses and experts as a real way to solve problem of plastic pollution. The basis is that kitchen waste recycling facilities use biological treatment technology that can effectively convert degradable plastic into fertilizer or gas. In addition, complex environmental impact of degradable plastics after processing in food waste processing plants is about 30% of impact of incinerators and 15% of landfills.
Comparison of prices for biodegradable and ordinary garbage bags
However, in reality, opposite is true: degradable plastic sent to food waste processing plants will not participate in fermentation process at enterprises at all. Pre-treatment of most objects will remove impurities in form of plastic products through several sorting processes, and remaining degradable plastic products that end up in biomass fermentation system are actually less than 5%.
A field study by Tsinghua University shows that most of degradable plastic currently entering biomass processing enterprises such as industrial composting and anaerobic fermentation, like traditional plastic, will be sorted out by equipment as impurities and not may end up in final product. environmental benefits of its decomposition characteristics cannot be realized in biomass decomposition fermentation process.
In terms of recycling and recycling, since countries around world have not yet set up separate recycling facilities for degradable plastics, differences between degradable plastics and traditional plastics in appearance and color are very small and difficult to pass through sorting machines by color and flotation machines, mechanical sorting machines, etc. to achieve efficient sorting. Due to inability to separate and recycle degradable plastics and traditional plastics, cost of recycling recycled plastic products mixed with degradable plastics will decrease by more than 20%. From this point of view, widespread use of degradable plastics to mix them into existing plastic recycling system is harmful and reduces the efficiency of plastic product recycling.
Partial excerpt from: Xinhua news agency client