Biodegradable plastics: a concept that needs to be correctly understood
The emergence of biodegradable plastics is regarded as a tool to deal with plastic pollution, especially to solve the environmental pollution problem of plastic food contact materials such as disposable straws. "It can disappear automatically without treatment" is a general public perception or expectation of biodegradable plastics.
However, in November 2015, the United Nations Environment Programme published the report "Biodegradable Plastics and Marine Garbage: Misunderstandings, Concerns, and Impact on the Marine Environment", calling for the elimination of misunderstandings caused by the "biodegradable plastic" label. The widespread use of products labeled "biodegradable" will not significantly reduce the amount of garbage that plastic enters the ocean, or reduce the physical and chemical risks that plastic poses to the ocean. Food plastic packaging marked with "degradable" or "100% degradable" is easy to be misunderstood by consumers, leading to an increase in random purchases and discards, which may exacerbate the problem of plastic pollution.
In April 2019, "Environmental Science & Technology" published a latest study by the University of Plymouth in the United Kingdom, pointing out that some plastic bags labeled as biodegradable can still be used normally after being placed for three years under different natural environmental conditions; the evaluated oxygen Degradable or biodegradable plastic bags do not show a better degradation effect than traditional plastic bags. The article once again aroused people's attention to the role of biodegradable plastics. The European Bioplastics Association, which represents the industry, questioned the scientific nature of the research and claimed that the research misled the value of biodegradable plastics and compostable plastics.
The bag marked as biodegradable can still be used normally after 3 years of seawater immersion
It can be said that the role of biodegradable plastics in the treatment of plastic pollution has been continuously debated. The reasons are that, in addition to the influence of unclear policies, unsound standards, and controversial scientific research, the public and industry have Unclear concepts and confusion are also an important reason, which leads to misuse, abuse of biodegradable labels, and even false publicity. Some typical misunderstandings include:
Equalize bio-based plastics as biodegradable plastics;
Treat degradable as fully biodegradable;
The biodegradation under industrial composting conditions is regarded as biodegradable in the natural environment.
01
Are bio-based plastics biodegradable plastics?
Not necessarily! Some bio-based plastics are biodegradable plastics, and some are not.
Biobased plastics are plastics produced under the action of microorganisms based on natural substances such as starch. The biomass used in the synthesis of bio-based plastics can be derived from corn, sugar cane or cellulose.
Biodegradable plastics (Biodegradable plastics) refer to the action of microorganisms under natural conditions (such as soil, sand, sea water, etc.) or under specific conditions (such as composting conditions, anaerobic digestion conditions or aqueous culture fluids, etc.). Bacteria, molds, fungi, algae, etc.) cause degradation, and eventually completely degrade the plastics that become carbon dioxide, water, methane, mineralized inorganic salts and new substances.
It can be seen that bio-based plastics are defined and classified based on the origin of material, while biodegradable plastics are classified from the perspective of the end of life. In other words, 100% of bio-based plastics may not be biodegradable, such as bio-PET and bio-PE, their chemical structure is no different from traditional petroleum-based PET or PET; while some traditional petroleum-based plastics It can be biodegradable, such as polybutylene terephthalate (PBAT) and polycaprolactone (PCL).
Types of bio-based plastics and petroleum-based plastics and their degradability
02
Can degradable be considered biodegradable?
Can't!
Plastic Degradation refers to the process of significant changes in structure and loss of performance under the influence of environmental conditions (temperature, humidity, moisture, oxygen, etc.). Specifically, it can be divided into mechanical degradation, biodegradability, photodegradation, thermal oxygen degradation and photooxidation degradation.
Whether a certain plastic will be completely biodegradable is affected by many factors, including crystallinity, additives, microorganisms, temperature, humidity, environmental pH, and length of time. When conditions are not available, many degradable plastics not only cannot achieve complete biodegradation, but may also have negative impacts on the environment and human health. For example, partially oxygen-degradable plastics (Oxo-degradable plastics) under the action of additives, only fragmentation of the material occurs and degrades into plastic particles invisible to the naked eye.
The main factors affecting plastic degradation
03
Compostable plastic = biodegradable plastic?
Not exactly equivalent, compostable plastics belong to a category of biodegradable plastics. Biodegradable plastics also include plastics that can be biodegraded in an anaerobic manner.
Compostable plastics (Compostable Plastics) refers to plastics under composting conditions, through the action of microorganisms, can be converted into carbon dioxide, water and mineralized inorganic salts of the elements contained within a certain period of time and new biomass, and finally formed Compost heavy metal content, toxicity test, residual debris, etc. should comply with relevant standards. Compostable plastics can be further divided into industrial compost and garden compost. Compostable plastics currently on the market are basically biodegradable plastics under industrial composting conditions.
Because compostable plastics are biodegradable under certain conditions, if you randomly discard compostable plastics in the natural environment (such as sea water, soil), these plastics degrade very slowly in the natural environment and cannot be completely degraded into carbon dioxide in a short time. And water, etc., its adverse effects on the environment are not substantially different from traditional plastics. In addition, studies have pointed out that if biodegradable plastic is mixed into other recyclable plastics, it will reduce the characteristics and performance of recycled materials. For example, the starch in polylactic acid may cause deterioration of the film made of recycled plastics such as holes and spots.
04
How to standardize and label biodegradable plastics?
China has no mandatory standards or regulations for biodegradable plastic labeling. The current relevant standard is GB/T20197-2006 "Degradable Plastics Definition, Classification, Marking and Degradability Requirements", which stipulates that the label of degradable plastics should include the main raw materials and composition information of the product, the degradation category or degradation method of the plastic, And the standard number. The requirements of the GB/T 20197 standard for labeling do not involve information such as the approved label, degradation assessment standard number, and whether it is recyclable.
GB/T 20197-2006 regulations on marking
The European Bioplastics Association recommends in its published guidelines: When a product claims to be biodegradable, the product should state what degradation standards (certification instructions and labels) it meets, the time for its complete degradation, and ensure that it completes the biodegradability. Location/condition of degradation process. North Carolina and Alabama in the United States enacted legislation in 2013 (HB 315, Senate Bill 298), requiring that plastic products marked with degradable, biodegradable or compostable should be marked with "not recyclable, do not recycle" at the same time to avoid Mixed into other recyclable plastic products. The following figure shows a more standardized biodegradable logo.
Standard plastic biodegradable label
Facing the environmental hazards of plastic waste and marine microplastics, the application of biodegradable plastics in food contact materials has received more and more praise and attention. my country's biodegradable food contact materials industry is facing a good development prospect. However, biodegradable plastics are not a panacea for plastic pollution. Only when they are used responsibly can their advantages and effects be brought into play. A clear definition of biodegradable plastics, standardization of labels, and effective public education are key measures to promote the healthy development of the biodegradable food packaging industry, develop a circular economy, and promote effective treatment of plastic pollution.
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