Due to COVID-19, personal protective equipment (PPE) such as masks and latex gloves has become a daily necessity in the world. Masks used to curb the spread of COVID-19 are paradoxically exacerbating another epidemic, plastic pollution. As such, the phenomenon in which two or more epidemics appear collectively at the same time, creating a synergism, and make the situation worse is called a "Syndemic." Ahn Yoon-joo, a professor of Department of Environmental Health Science at Konkuk University, emphasized that "the two crises coexist and their effects are synergistic, so the two should be quarantined together."
Plastic used in medical supplies
The most common waste in the COVID-19 era is medical waste and masks, not delivery containers, delivery boxes, or plastic gloves. In addition to medical supplies such as needles and bandages used in the treatment process, all items used by patients are treated as quarantine medical waste. Syringes used in vaccination injections and medical devices are only disposable for sterile environments and manufactured out of plastic.
Especially among those medical waste, masks have become a necessity for blocking respiratory droplets and virus prevention. According to The Anti-Corruption & Civil Rights Commission, Koreans used one mask per 2.3 days as of March last year. If 20 million abandoned masks are thrown away per day, more than 7.3 billion are poured out annually. According to the American Chemical Association, about 129 billion disposable masks are being used every month around the world.
The mask filter part is usually composed of triple filters, and more than 98% are made of polypropylene (PP) materials that do not decompose quickly in the environment. PP is easy to shape, highly durable, and is used in cooking utensils because environmental hormones are not emitted. However, disposable masks cannot be recycled and are being classified as general waste and are buried and incinerated.
The PP component of the mask is harmless to the human body, but when it is incinerated, harmful substances such as carbon monoxide and dioxin are released. Dioxin is a substance designated as a first-class carcinogen by the World Health Organization (WHO), and when absorbed by the human body, it can have fatal effects such as the birth of a deformed child, cancer, and metabolic and hormonal abnormalities.
Biodegradable plastic that has emerged as a solution
To solve those problems caused by the waste of plastics, scientists are paying particular attention to the so-called “biodegradable plastic”, a clean plastic that rots or melts away. Biodegradable plastic is a plastic that naturally decomposes in the environment. Microorganisms in the natural environment metabolize and break down biodegradable plastics. Common plastic usually does not decay but remains semi-permanent for hundreds of years, even if it is buried in the ground. On the other hand, biodegradable plastic rots away when buried in the ground.
Biodegradable plastics are divided into two main types. The first is derived from biomass, which is made by polymerizing macromolecular monomers. The other is produced using petrochemical raw materials such as PBAT (Polybutylene Adipate Terephthalate). Typical biodegradable plastic includes mostly starch-derived Poly Lactic Acid (PLA). PLA is produced by fermenting starch from corn and sugar cane to form lactic acid and polymerizing it. It can be biodegradable in about six months under compost conditions and has the advantage of not producing harmful substances.
In Korea, research using biodegradable plastics is currently underway to solve the problem of abandoned masks. Hwang Sung-yeon, head of the center for bio-based chemistry at the Korea Research Institute of Chemical Technology, developed a new concept of a biodegradable mask filter in March this year. It is easy to breathe through, can be used several times, and it compensates for the shortcomings of the existing mask filter as it decomposes 100% naturally under composting conditions within a month.
The research team reinforced for poly butylene succinate (PBS), a representative biodegradable plastic, and then supplemented the difficulty of breathing by overlapping microfibers with nanofibers. The chitosan nanowhisker, a chitosan nanoparticle, was coated to help viruses and fine dust stick to it. In addition, people could reuse the chitosan coated mask, because it overcomes the limitation of vulnerability to moisture.
Limitations of biodegradable plastic
Biodegradable plastics still have many obstacles that cannot be overcome to replace regular plastics. According to United Nations Environment Programme (UNEP), there are very few situations above 50℃ in the natural environment, the temperature at which biodegradable plastic breaks down. When PLA is buried, it naturally decomposes like compost, but it must meet demanding conditions of temperature above 58℃ and moisture above 70%. Only when these conditions are met will they decompose more than 90% over a half-year period. Biodegradable plastics are rotting too slowly, causing microplastics to form.
Dr. Imogen Napper, a marine environmental scientist at the University of Plymouth in the UK, published the results of an experiment on natural environmental degradation of biodegradable plastic in June 2019. Plastic bags made of biodegradable plastic were treated under three conditions: land reclamation, abandonment in the sea, and exposure to air, and then the state of their decomposition was checked three years later. They remained intact in the ground three years later. The situation was the same at sea. The damage to what was left in the air was so small that it was difficult to distinguish it from the new one.
Natural resource recovery expert Richard McKinley warned,
“People think biodegradable, bioplastics are unconditionally eco-friendly.
But the reality is not so simple.”
A method under study to overcome the limitations of biodegradable plastic
According to United Press International (UPI), Dr. Sheeting, a professor of materials and chemical engineering at the University of California, Berkeley, announced in the journal Nature that he has developed a new way to quickly and properly breakdown biodegradable plastics. The research team mixed enzymes that eat PLA during the plastic manufacturing process. As a result, PLA fibers were broken down in a week. In other words, by using enzymes, the aforementioned tricky conditions for biodegradable plastics to decay have been mitigated.
Existing biodegradable plastics produce microplastics as biodegradation progresses, but the enzyme-based method turns 98% of PLA into monomers with small molecular weight. Now, the remaining challenge is commercialization. To distribute biodegradable plastics with enzymes, people must be able to be produced cheaply and in large quantities. Hoping that more improved degradation enzymes will emerge to address the problem of plastic waste, scientists around the world are continuing to study plastic degradation using enzymes.
Disasters such as the COVID-19 can occur again every five or ten years. Dr. Shim Won-joon, a researcher at the Korea Institute of Ocean Science and Technology, said, "We are wearing masks without control because quarantine is a priority, but if we prepare for the prolonged COVID-19, we need to find scientific guidelines about the indiscriminate discharge of masks." Humans need to develop real biodegradable plastics that do not leave microplastics, and it is also important that our efforts continue. He also warned, "We should not ignore environmental issues just because we are stuck in a danger from the virus." People need to always think that their behavior would come back and have a good or bad influence on their lives. It is important to be alert and act voluntarily to reduce plastics.