The emergence of biodegradable plastic bags 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.
It can be said that the role of biodegradable plastics in the treatment of plastic pollution has been constantly debated. The reasons for this are that, in addition to the influence of unclear policies, unsound standards, and controversial scientific research, the public and industry have The unclear and confusing concept of biodegradable plastics is also an important reason. Some typical misunderstandings include:
1. Equal bio-based plastics as biodegradable plastics;
2. Treat degradable as fully biodegradable
3. Consider the biodegradation under industrial composting conditions as biodegradable in the natural environment.
Regarding biodegradable plastics,
We must have a correct concept.
Bio-based plastics, biodegradable plastics? ●●
Bioplastics not only refer to the biological raw materials used in the plastic but also refer to the biodegradability of the plastic.
"Bio-based" is defined as "derived from biomass" in European standards. Therefore, bio-based plastics are plastics that are wholly or partly derived from biomass. Biomass is a raw material of biological origin, excluding raw materials embedded in geological structures or petrochemicals.
Biodegradable plastics refer to plastics that can be decomposed by microorganisms (bacteria or fungi) into the water, naturally occurring gases such as carbon dioxide (CO2) and methane (CH4), and biomass (such as the increase in the number of microorganisms). Biodegradability largely depends on environmental conditions: temperature, microorganisms, the presence of oxygen and water.
Classification of degradable materials ●●
Degradable materials can be divided into four categories: photodegradable plastics, biodegradable plastics, photo/biodegradable plastics, and water-degradable plastics.
Photodegradable plastics are photosensitizers mixed into plastics. Under the action of sunlight, the plastics gradually decompose. But its disadvantage is that the degradation time is affected by sunlight and climate environment, so it cannot be controlled.
Biodegradable plastics refer to plastics that can be decomposed into low-molecular compounds under certain conditions by microorganisms that exist in nature, such as bacteria, molds, and algae. Such plastics are convenient to store and transport and have a wide range of applications.
Water-degradable plastic is a plastic that can be dissolved in water because of the addition of water-absorbing substances. With the development of modern biotechnology, biodegradable plastics have become a new hot spot in research and development.
Can degradable be considered biodegradable? ●●
The degradation of plastics 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 biodegraded is affected by many factors, including crystallinity, additives, microorganisms, temperature, humidity, environmental pH, and length of time. When the conditions are not available, many degradable plastics not only cannot achieve complete biodegradation but may also have negative effects on the environment and human health. For example, under the action of additives, some oxygen-degradable plastics will only fragment and degrade into plastic particles invisible to the naked eye.
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 plastic refers to that plastic can be transformed into carbon dioxide, water, mineralized inorganic salts of the elements contained in it, and new biomass in a certain period of time through the action of microorganisms under composting conditions, and the content of heavy metals in the final compost, Toxicity test, residual fragments, 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.