Is Biodegradable Plastic Good for the Environment? Exploring its Advantage and Disadvantage.

Plastic litter pollution in the oceans is increasingly emerging as a serious global environmental concern. Since 1950, approximately 8.3 billion tons of plastic have been produced, with an estimated 6.3 billion tons disposed of as waste. Notably, ocean plastic litter stemming from discarded plastic containers washed into the sea has gradually deteriorated, fragmenting into microplastics. This process causes ecological and marine environmental degradation, garnering widespread attention.

"Biodegradable plastics" have been proposed as a potential solution to the aforementioned plastic waste dilemma.

This article delves into the technology, benefits, and drawbacks of biodegradable plastics.

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*Information accurate as of September 2023.

What is biodegradable plastic?

Biodegradable plastics are plastics that degrade under specific conditions after use. They can be handled similarly to general plastic products, but after use, they degrade at the molecular level through the action of microorganisms present in the natural environment, ultimately transforming into carbon dioxide (CO2) and water (H2O).

Types of biodegradable plastics

Biodegradable plastics can be categorized into three groups based on raw materials and manufacturing methods. The details are outlined below.

●Microbially produced: Biodegradable plastics are manufactured utilizing microorganisms.
●Natural extracted: Derived from cellulose found in plants, corn, other grains, potatoes, and similar sources.
●Chemically synthesized: Produced through chemosynthetic reactions.

The following are examples of substances in "biodegradable plastics" based on the aforementioned classification.

Table 1: Representative examples of biodegradable plastics
(Reference source: National Institute for Environmental Studies)

Classification Examples of representative substances
Microbially produced Polyhydroxyalkanoate (PHA)
Bacterial cellulose
Natural extracted Chitosan/cellulose/starch
Cellulose acetate
Esterified starch
Biodegradable plastic/starch mixture system
Chemically synthesized Polylactic acid (PLA)
Polybutylene succinate (PBS)
Polycaprolactone (PCL)
Polybutylene adipate terephthalate (PBAT)
Modified polyethylene terephthalate
Polyglycolic acid (PGA)
Polyvinyl alcohol (PVA)

Among the representative substances, the following provides an overview of the four substances that have garnered attention (highlighted in yellow in Table 1).

PHA (polyhydroxyalkanoate)

Polyhydroxyalkanoates (PHAs) are storage compounds that accumulate in the bodies of various microorganisms.

PHA is produced through bacterial fermentation processes using vegetable oils and other raw materials.

After use, PHA undergoes rapid degradation in soil and seawater, converting into water and CO2. Thus, PHA is anticipated to replace plastics derived from fossil fuels.

Given PHA’s brittleness, polyesters copolymerized with monomers have been developed to enhance strength, serving as raw materials for rigid injection-molded products and films.

PLA (polylactic acid)/PHA (polyhydroxyalkanoate)

Polylactic acid (PLA) is synthesized through a polymerization reaction of L-lactic acid, obtained via starch fermentation.

Corn-derived starch is commonly utilized as a raw material. This starch undergoes enzymatic hydrolysis and fermentation to yield L-lactic acid, which is then subjected to chemical polymerization to form polylactic acid.

While biodegradable, PLA exhibits slow decomposition under standard conditions and breaks down gradually in soil or water. However, in composting facilities, it decomposes almost entirely within approximately six months.

Due to its low heat resistance and transparency, PLA finds applications as packaging material for frozen foods, plastic bags, agricultural sheeting, and greenhouse films.

PBS (Polybutylene Succinate)

Polybutylene succinate (PBS) is a polymer compound possessing excellent properties akin to polyethylene.

Technology has been developed to manufacture it from biomass materials, and it is garnering attention as a promising biodegradable plastic.

Applications incorporating it include agricultural mulch film, garbage bags, and food packaging materials.

PCL (Polycaprolactone)

Polycaprolactone (PCL) is a biodegradable plastic synthesized from petroleum-derived raw materials and degraded by bacteria.

Leveraging its low melting point and thermoplastic properties, PCL finds use in agricultural mulch film, compost bags, as well as in paints and fibers.

Advantages and applications of biodegradable plastic

Biodegradable plastics offer significant environmental benefits due to their ability to decompose naturally through the action of microorganisms, ultimately breaking down into water and carbon dioxide. This decomposition is especially effective in compost systems, where these plastics contribute to the production of high-quality organic fertilizer without negatively impacting its quality. Additionally, when incinerated, biodegradable plastics have a low calorific value, which prevents damage to incinerators and minimizes atmospheric pollution. These characteristics make biodegradable plastics ideal for products used in natural settings or in applications where recycling is challenging.

The following table summarizes the fields and applications where biodegradable plastics find utility.

Table 2: Fields where biodegradable plastics are used
Source: Green Japan (partially quoted and reconstructed from data)

Fields of application Applications/functions Examples of specific products
Fields used in the natural environment Agricultural and forestry materials Mulch film for agriculture, seedling pots for transplanting
Fisheries materials Fishing line, fishing net, etc.
Civil engineering and construction materials Insulation materials, civil engineering formwork, sandbags, water retention sheets
Outdoor and leisure use Disposable products for camping, barbecues, cherry blossom viewing, etc.
Fields where it is difficult to recover and reuse products after use, or where it is effective to convert Food packaging films and containers Fresh food trays, instant food containers, fast food containers
Sanitary products Paper diapers, sanitary products
Office supplies, daily necessities, stationery, miscellaneous goods, etc. Pen cases, razors, toothbrushes, cups, garbage bags
Fields utilizing special functions Slow-release (gradual release of contents) Coating materials for pharmaceuticals, agrochemicals, fertilizers, etc.
Water retention/absorbency Afforestation materials for use in deserts, wastelands, etc.
In vivo degradation and absorption Surgical sutures, bone fracture fixation materials, nonwoven fabrics for medical use
Small oxygen permeability, non-absorption Food packaging film, internal coating of paper packs for drinking
Low melting point Adhesive for packaging and bookbinding

Concerns and disadvantages of biodegradable plastics

Limited degradation conditions

Biodegradable plastics decompose in environments such as soil or water, or in compost. In other words, creating an environment conducive to microbial activity is crucial for plastics to decompose effectively.

Long decomposition time

Biodegradable plastic agricultural mulch film typically takes several months or longer to decompose, while biodegradable plastic garbage bags break down into smaller pieces more quickly.

The rate of degradation of biodegradable plastics is highly reliant on microbial activity and the surrounding environment.

High production costs

Biodegradable plastics generally incur higher production costs compared to conventional plastics. This is due to the labor-intensive development and production processes. Additionally, the utilization of plant-derived raw materials increases raw material costs in contrast to fossil fuels (e.g., petroleum).

Potential hindrance to recycling systems

While biodegradable plastics naturally degrade, the recycling process to reuse them as recycled resin may become challenging.

In particular, if marine biodegradable plastics* become predominant in the future, reusing them may become challenging, leading to a higher proportion being sent to landfills or incinerated, potentially impacting the recycling system.

*Marine biodegradable plastics: Plastics that are degraded in the ocean by the action of enzymes produced by microorganisms.

Other concerns (consumer complaints in the U.S.)

Biodegradable plastic snack food packaging labeled as "compostable" has sparked consumer complaints.

The "100% compostable package" faced criticism from users due to the bag wrinkling and emitting a loud noise when snacks were removed. Eventually, the manufacturer introduced a different biodegradable product that was "quieter," resolving the issue.

These early efforts in using biodegradable plastics underscore the importance of "anticipating and addressing new challenges proactively from the consumer's perspective."

Taking action on environmental issues in plastic waste

Addressing environmental concerns in plastic waste involves promoting biodegradable plastics, biomass plastics, and material recycling with mono-materials. The benefits are as follows.

Biodegradable plastics possess the ability to decompose in the natural environment, reverting to soil and seawater. Conversely, biomass plastics utilize renewable organic resources like plants as raw materials, reducing reliance on fossil fuels such as petroleum. Moreover, the adoption of "mono-materials" facilitates efficient material recycling, contributing to the realization of a circular economy.

Below is an in-depth overview of the current challenges and strategies for the three initiatives.

Promotion of biodegradable plastics

There are four major challenges to the widespread use of biodegradable plastics:

1. Technical issues in biodegradable plastics manufacturing
2. Establishment of evaluation and certification systems for manufactured products
3. Development of composting facilities
4. Reduction of production costs

Currently, only about seven types of biodegradable plastics are in practical use (refer to Table 1), necessitating ongoing development of new plastics that match the functions and performance of fossil fuel-based counterparts.

Establishing test methods to evaluate biodegradability and ensuring safety evaluation methods are essential. However, the presence of multiple standards and specifications for biodegradable plastics in Japan warrants attention. Additionally, the lack of consumer awareness leads to the improper disposal of biodegradable plastics mixed with regular plastic collection.

In Japan, the Japan BioPlastics Association (JBPA) was founded in 1989 with the objective of advancing and commercializing biodegradable plastic technology.

The JBPA has instituted the "Green Plastic Identification and Labeling System" to authenticate biodegradability and safety. Products meeting the JBPA's screening criteria are permitted to display the "Biodegradable Plastic" mark.

Various standards for biodegradable plastic test methods have been established in the Japanese Industrial Standards (JIS), while the International Organization for Standardization (ISO) oversees standards abroad.
Other initiatives to promote dissemination include "expanding composting facilities" and "achieving cost reduction through economies of scale," which serve as focal points for future enhancements.

Promotion of biomass plastics

"Biomass plastic" refers to plastic derived from plant-based materials. Originally, it was categorized as carbon-neutral because it utilizes plant-derived materials (plants absorb CO2 and water for growth), thereby not contributing to the increase in CO2 concentration in the atmosphere.

To encourage the adoption of biomass plastics, the Japanese government ratified the Kyoto Protocol in June 2002, followed by the announcement of the "Biomass Nippon Strategy" in the same year. Subsequently, in 2021, it formulated a "Roadmap for Bioplastics Introduction" and is actively promoting the implementation of measures among bioplastics manufacturers, users, retail service providers, and others.

The following four issues need to be addressed to promote the use of biomass plastics:

1. Higher price compared to materials derived from fossil fuels (e.g., petroleum).
2. Some biomass plastics do not biodegrade.
3. Certain biodegradable biomass plastics, assumed to degrade on the ground by microorganisms, do not easily degrade in the ocean.
4. The raw materials for biomass plastics are crops such as sugarcane and corn, so increasing production for bioplastics will impact sales of food crops.

Solutions to the above issues need to be presented systematically in the future.

Promotion of material recycling through mono-material

The "Strategy for Strengthening Material Innovation Capabilities," formulated by the Japanese government on April 27, 2021, sets the following goals to realize a circular economy:

1. Effectively use 100% of used plastics through reuse and recycling by 2035
2. Introduce approximately 2 million tons of biomass plastic by 2030
Specific efforts to achieve these goals are outlined as follows:

●Establishment of materials and product design technology (mono-materials) based on reuse and recycling, and formulation of product design guidelines
●Improvement of efficiency and sophistication of material recycling and chemical recycling technologies to achieve compatibility with carbon neutrality

Thus, "material recycling through mono-material" aligns with government policy.

DNP contributes to the mono-material packaging

DNP's mono-materials technology

DNP's mono-materials technology boasts two key features. Firstly, the materials are designed for easy recycling, reducing recycling burdens and enhancing the quality of recycled materials.

Secondly, they offer superior protection for the contents of product packages. DNP's mono-material packaging materials utilize proprietary converting technology to replace conventional composite materials.

DNP mono-material packaging materials lineup

DNP offers mono-material packaging materials in two types: PE (polyethylene) and PP (polypropylene). Depending on the intended use, they can be utilized for products such as pouches and tube containers.

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