Biodegradable plastic and marine plastic litter

1.Marine plastic litter

Marine plastic litter is a global-scale issue that has been covered by the mass media on a daily basis. TV media has also covered the movement of replacing single-use plastic products, -such as straw, packaging, bags, and cutlery, to products made of biodegradable or plant-based raw materials. The “Osaka Blue Ocean Vision,” which aimed to reduce additional pollution from marine plastic litter to zero by 2050, was shared as the leaders’ declaration during the Group of Twenty (G20) summit held in Osaka, Japan, on June 2019. The Japanese Ministry of Environment (MOE) established the Subcommittee for the Resource Recycling Strategy for Plastics in the financial year (FY) 2018 to play a coordinating role as the presidency holder. The Subcommittee compiled the results from surveys conducted previously and submitted the report to the MOE. From these, the Resource Circulation Strategy for Plastic was conceptualized on May 31, 2019.

This Subcommittee was initially not established to specifically discuss ocean plastic litter, but to discuss the cyclic use of plastic as resources (i.e., reuse and recycle). Addressing the domestic and international requirements to discuss the litter generated by cyclic use, especially ocean plastic litter, was only added to the agenda later on. Their strategy specifically addressed the need to eliminate littering and illegal dumping, which cause ocean plastic litter.

Furthermore, enhancing sustainability, using recyclable materials (recycled products), and renewable resources (paper and biomass plastic) were highly recommended. These aimed to promote the use of renewable resources, encourage the replacement of plastic made by fossil fuels, and lower the dependence on it. Meanwhile, biomass plastic widely known as a plant-based plastic made of plant-derived resin component, has also been introduced.

A similar term, i.e., “bioplastic,” has been introduced in recent years. Figure 1 shows the relationship between biomass plastic and biodegradable plastic. “Bioplastic” is a generic word that is derived from biomass plastic. The latter is decomposed to carbon dioxide (CO2) and water (H2O) under specific conditions by microorganisms found in nature. Biodegradable plastic includes plastics made of non-renewable resources, such as petroleum.

2.The positioning of biomass plastic

The report submitted by the Subcommittee for Resource Circulation Strategy for Plastic to the MOE clearly indicated the numeric goal that biomass plastic of about 2,000 thousand tons should be used by 2030. This amount came from the goal indicated in the fourth version of The Basic Act of Sound Material-Cycle Society (“The Basic Act”) on July 19, 2018, which stated that the domestic sales amount of biomass plastic should reach 1,970 thousand tons in FY 2030. Actually, the goal of The Basic Act was based on that stated in the Plan for Global Warming Countermeasures established on May 13, 2016. Therefore, the goal is based on the amount of CO2 emission cuts.

The Plan for Global Warming Countermeasures was considered based on the Intended Nationally Determined Contribution of Japan, which established that the emissions should decrease by 26.0% by FY 2030, compared with the emission decrease in FY 2013 (25.4% decrease from the rate reported in FY 2005). As for the background of establishing the plan, it was largely influenced by the Fifth Assessment Report by the Intergovernmental Panel on Climate Change (IPCC) and the Paris Agreement. Biomass plastic aim to replace petroleum-based plastic products, especially, given that the latter are difficult to recycle and require burning to disintegrate them. Familiarizing biomass plastic is one of the countermeasures for cutting non-energy-originated CO2 emissions and replacing petroleum-based plastic to biomass plastic aim to decrease CO2 emission when plastic waste is burned. This idea represents the “carbon neutral” concept.

In the process of establishing how much CO2 emissions decrease should be achieved, the amount of CO2 absorbed by plants in FY 2030 has been estimated to be about 2,090 thousand tons for biomass plastic. Meanwhile, the domestic sales of biomass plastic have been estimated to be about 1,970 thousand tons. These values were calculated from the data obtained from the Greenhouse Gas Inventory. This database summarizes the official data and calculates the annual amounts of greenhouse gas emissions and absorption (

According to the report published by the Japan Bioplastic Association on September 19, 2018, the amount of domestic sales of bioplastics reached 39.5 thousand tons in 2017 (estimate figure). The same report indicated that the global capacity of bioplastic production in 2017 was 2,050 thousand tons. Furthermore, the composition of biomass plastic in bioplastic was indicated in the report; however, making a comparison is difficult, because the definition of biodegradable bioplastic is different in the statistical data (the overlapping part in Figure 1). In Japan, the biodegradable bioplastic is included in biomass plastic in some of the data, because the sales amount is categorized based on how these are used. However, something that has degradability is included in the degradable plastic category statistical data on total production capacity. According to An Introduction to Plastic recycling 2018 published by Plastic Waste Management Institute, the annual sales amount of plastic in Japan is about 10 million tons, with bioplastic only comprising about 0.4% of the total. The amount of biomass plastic is less than that of bioplastic; therefore, in order to achieve the numerical goal of 2,000 thousand tons, the amount of biomass plastic should be increased by about 50 times more. However, this could be a difficult task given that the current global bioplastic production capacity is about 2,000 thousand tons.

Biomass plastic requires plant as its raw material. Given that farmland, water, and energy are required to grow the plants to be used in the production, biomass plastic should be comprehensively evaluated with life cycle assessment as they can discharge more CO2 than petroleum-based plastics in some cases.

3.Present status of biodegradable plastics

Biodegradable plastics biologically decompose into carbon CO2 and H2O; therefore, they are useful for prolonging landfill life. Biodegradability occurs as a result of microorganisms’ activities and take some time to be completed. As non-biodegradable plastics, they break down into tiny pieces step by step, after which they eventually decompose into CO2 and H2O. Therefore, biodegradable plastics are expected to solve the microplastic issue, because they continue to decompose until they become CO2 and H2O.

Biodegradability is activated in soil, water (ocean, lake, pond, river, etc.), and the digester. The digester is an artificial facility, which is engineered to easily activate the microorganism and process the organic composition into compost. The biodegradable plastics are decomposed by microorganisms into CO2 and H2O under the aerobic condition in the presence of oxygen (O2). It can also be decomposed into CO2, H2O, and methane under the anaerobic condition, in which there is no O2. This process, called “bio fermentation,” is how bio gas (the mixture of methane and CO2) is created. As activating biodegradability requires the specific condition, the ISO or JIS standard has been established for each environment or condition in use. Table 1 shows the testing standards for biodegradability on plastics. For discussion, the ocean is classified into four categories: shoreface (ISO/CD 22404), shallow seabed (ISO 18830, ISO 19679), in sea water (ISO/NP 23971), and real sea area (ISO/CD 22766) based on the differences in the microorganism species, wave force, the amount of ultraviolet light, and O2 concentration, among others.

After the G20 summit in Osaka, the Exploratory Committee for the Standardization of Ocean Biodegradable Plastics was established in Japan, thereby initiating the continued discussions on biodegradable plastic in soil, the use of biodegradable plastic, and the process of waste management. The European Strategy for Plastics in a Circular Economy, established in 2018, suggested defining biodegradable plastic and using clear labeling so that these can be collected separately and composted efficiently. As a substitute material, it is expected to minimize the environmental load compared to non-biodegradable plastics. However, it should be discharged into the environment properly. Hence, it has been suggested that littering and illegal dumping of biodegradable plastics should be prohibited.

Cellulose, the main component of paper and a natural polymer compound, is expected to be used widely. Cellulose has the characteristic of biodegradability, but it requires a specific condition to activate. Thus, littering and illegal dumping of cellulose should also be prohibited. The cellulose waste products should be processed following the rules of each local government.

4.The philosophy for the future society

The Resource Circulation Strategy for Plastic mentioned the edification not only for local governments but also for business owners and consumers. Proper infrastructure development should be conducted to evaluate any business activity while considering the environment, society, government investment, and ethical consumption of this product due to its rising popularity worldwide. In order to promote the use of recyclable materials and bioplastic, the authorities should obtain a comprehensive picture of the market demand, such as through public purchase by the national and local governments based on the Act of Promoting Green Purchasing. Incentive should also be introduced based on recycling systems, along with the authentication of legitimate low-carbon products. Finally, these materials should be further popularized among the consumers. All these can ensure sustainable consumption, which is one of the Sustainable Development Goals mentioned earlier.

The issues in this article, however, are the tip of the iceberg. The fact remains that there is no conclusive solution on issues, such as those involving natural resources and environment, even if these have been discussed for a long time. The society, lifestyle, and set of values are changing time, and those issues are expected to change as well. Therefore, we ought to continue seeking solutions, and the first step should be finding more supporters and cooperative stakeholders with whom we can work together.

August 17, 2020 – Hitoshi Sugiyama, translator

This is a translation from the Japanese original article written by Kazukiyo Nagai, which was published on August 19, 2019.