Plastic restrictions and bans

According to an environmental report published by the British magazine "Nature•Communications", it is estimated that 52,000 tons of microplastics end up in the ocean every year. Every year, 20,000 tons of plastic microparticles are discharged to remote snow-covered areas. I believe you must have seen the pictures of many marine animals that are full of plastic products and die in pain.

In response to these problems, most countries have issued a series of policies and regulations to restrict the production, sales and use of plastic products. We call it a plastic restriction or a plastic ban. Facing the huge demand from all walks of life, the opportunity for "degradable" plastics is coming. But is this really the case? "

Cost

In the market economy environment, it is meaningless to talk about any issue without cost.

The current degradable plastic lunch box is in an embarrassing situation where the cost is not dominant. Before talking about this issue, it is necessary to explain the difference between degradable plastics and traditional plastics.

There are five main types of common plastics in life, namely polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS) and acrylonitrile-butadiene-styrene copolymer ( ABS) five categories of plastics. The raw materials of these five kinds of plastics are petroleum, which are non-degradable plastics.

And what we usually call non-polluting environmentally friendly materials generally refers to "biodegradable plastics", which are plastics that are wholly or partly derived from biomass. Biomass is a raw material of biological origin, excluding those embedded in geological formations or petrochemicals. Plastics that can be broken down by microorganisms (bacteria or fungi) into water, naturally-occurring gases such as carbon dioxide (CO2) and methane (CH4), and biomass (such as growth in microbial populations). Of course, biodegradability is highly dependent on environmental conditions: temperature, microorganisms, the presence of oxygen and water.

Petroleum-based degradable plastics are plastics produced from fossil energy, mainly including PBS (polybutylene succinate), PBAT (polybutylene adipic acid/terephthalate), and PCL (polybutylene succinate). esters) etc. Bio-based degradable plastics are plastics produced from biomass, which can reduce the consumption of traditional energy such as petroleum, mainly including PLA (polylactic acid), PHA (polyhydroxyalkanoate), PGA (polyglutamic acid), etc. . Taking PLA, the most common biodegradable plastic in life, as an example, the unit price of its raw materials is 25,000 to 30,000 yuan per ton, while the raw material price of one ton of polypropylene is generally around 80-130 million yuan. The prices of the finished products of two different materials are more able to explain the problem.

The high cost limits the promotion of degradable plastic lunch boxes. The more serious situation is that many plastic lunch boxes with the concept of "degradable" have come to the opposite of environmental protection.

"Pretend" degradation and "conditional" degradation

When there is a huge price disparity between non-degradable and degradable lunch boxes, there is enough "business opportunity" in the middle ground.

Among the degradable plastics in a broad sense, in addition to biodegradable plastics represented by PLA, there are also plastics that can be mechanically split, such as starch-filled, photodegradable, and oxidative degradation of these "pseudo-degradable" plastics.

Photodegradable plastic means that the material will automatically degrade under the action of light. Many photolytic plastics are made of photosensitizers added to the material, which become smaller powders under light conditions. There are also some so-called degradable lunch boxes that add a certain percentage of starch, and through the biodegradation of starch, the physical properties of the material collapse. The decomposed PE, PP, PVC, etc. not only cannot be absorbed by the environment, but will remain in the environment because they are invisible to the naked eye, causing greater harm. Therefore, developed countries such as the European Union and the United States have already classified such products as phase-out.

Compared with some products that sell dog meat, materials such as PLA can at least theoretically achieve purer degradation products. But in practice, it may still not meet our expectations.

A report from a research institute shows that, taking PLA as an example: "If a PLA bento box is thrown into the sea, it will take hundreds of years to decompose." The report states that PLA will decompose in industrial composting facilities, "there, PLA It can be heated to a high enough temperature that the microorganisms can decompose at an impressive rate."

Research institutions and environmental protection volunteers have done similar experiments in real environments: in 2014, the Central South University of Forestry and Technology in China simulated natural soil and tested PLA plastic for 12 months, and its quality only lost 0.23% after 12 months; The 400-day test at Leuter University was placed in seawater and fresh water, and the final mass loss of PLA was only about 0.5%; this is another situation faced by many biodegradable plastics, that is, the theoretical degradation conditions are not in reality. allow.

PLA materials require composting to degrade, but are there current facilities dedicated to composting these materials? Even if we solve it with the idea of recycling, it is difficult to distinguish traditional plastic bags from degradable plastic bags. In recycling, if plastic pellets are produced uniformly, materials such as PLA will affect product quality; when uniformly degraded, traditional plastics will become impurities.

In addition, PLA materials need to consume corn and other food crops to ferment to produce lactic acid. The output of grain crops is affected by many factors such as harvest conditions and international markets, and the source may have greater volatility. Therefore, biodegradable plastics represented by PLA and other materials look beautiful, but there are still many insurmountable obstacles at this stage.

There is still controversy about the "plastic ban"

Why is plastic banned repeatedly? In fact, the most fundamental reason is because it is so easy to use. There is no material on the planet that is as tough, lightweight, hygienic and inexpensive as it is, and it has penetrated into the face of life. Those who advocate a total ban on plastic production online can imagine what a plastic-free world would be like.

Even in the face of the environmental hazards that plastics may cause, there are still many controversies on the topic of banning plastics.

A team of academics from Heriot-Watt University in the UK argues that much of the current debate about reducing or banning plastic is often short-sighted rather than fact-based.

Professor David Bucknall, head of the Department of Materials Chemistry at the Institute of Chemical Sciences, estimates that replacing plastics with existing materials will double global energy consumption and triple greenhouse gas emissions. Another analysis found that the environmental cost of replacing plastic is nearly four times as high. Replacing plastics with alternative materials, such as glass and metal, would be more expensive to manufacture due to energy consumption and resources required for processing, including water, he explained. In addition, replacing lightweight plastics means higher transportation costs and higher greenhouse gas emissions from burning more fuel.

The book "Fake Environmental Protection" written by Kunihiko Takeda, a Japanese scholar, believes that the raw materials of plastic bags are made from refined petroleum residues. If they are properly recycled, plastic bags will not cause more petrochemical waste pollution, and even No more oil is wasted.

A 2011 study by the UK Environment Agency stated that we have been promoting non-woven bags for plastic bag replacement products, which have much higher carbon emissions than plastic bags after disposal, and need to be reused at least 11 times to make up for it. pollution. To reach the same level, the cotton bag would need to be reused 131 times.

Think

Just like two sides of a coin, the development and ban of plastics reflect the contradictions in the pursuit of different values in the process of human civilization. It is this contradiction that drives us to constantly think about a more perfect solution. But at this stage, we need to have a rational understanding of plastics, and sometimes a "ban" is not enough to solve all problems. The problem of plastic pollution is also faced with some deficiencies in technology, terminal disposal, and public awareness. The public's enthusiasm for environmental protection is very high, but lack of some professional knowledge often leads to the opposite side of things. For us ordinary people, demonizing plastic is neither necessary nor pointless. In fact, under the premise of ensuring the quality of life, minimizing the generation of waste, doing a good job in sorting and reducing waste, reusing what you already have, and avoiding disposable products as much as possible is the greatest responsibility for yourself and the environment.