General Explanation

 

There is still a lack of reliable data and short of scientific knowledge on marine plastic debris. Although we should take some actions, based on the precautionary principle, we also need to enrich scientific knowledge in various fields, such as monitoring method, flow of macro- and microplastics in the ocean, impact of to ecosystem and human health, material flow analysis, life cycle assessment, and others. RKC-MPD is planning to organise some seminars and working groups to review the current status of relevant research and to facilitate future research in the region.

Life Cycle Assessment

 

Life Cycle Assessment (LCA) is a tool to assess the potential environmental impacts of any stage in life cycle of products or services, from extraction of resources, production, consumption, to reuse, recycling, or final disposal. In the context of combatting marine plastic debris, reducing the use of plastic is essential to prevent leakage from the source. However, some LCA research on plastics and plastic products indicate that replacing plastics with alternative materials is not always an environmentally friendly choice, at least when it comes to climate change impact.

Ayudhaya (2014) compiled some comparisons that emphasise that plastics are still essential to address climate change. Chaffee and Yaros (2014) found that conventional polyethylene bags are more environmentally friendly than paper bags and compostable bags, especially in terms of fossil fuel use, municipal solid waste, greenhouse gas (GHG) emission, and freshwater use. Huang and Ma (2004) revealed that almost all kinds of plastic packaging have significantly less environmental impact than aluminium, glass, steel, and cardboard packaging. The ban on plastic bags was not effective in reducing GHG emission, especially in municipalities where they have been reused and recycled (Nishijima and Nakatani, 2016). Municipalities should find alternative products or materials for disposing of their waste or provide materials for recycling instead of plastic bags.

The Plastic Circulation Cooperation in Japan found that the use of plastic packaging in distributing fruit (peaches and strawberries) is efficient in reducing the amount of fruit damaged as a result of vibration in distribution trucks (Plastic Circulation Cooperation, 2017). Plastic packaging reduces food loss and environmental loads (GHG emission and energy consumption). For example, in an average distribution distance of 324 km, food loss from plastic-packaged fruit was only 0.1%, compared with 73.4% of fruit without plastic packaging. As for impacts, plastic-packaged fruit reduced 69% of GHG emissions and 66% energy consumption.  

Future studies should assess more comprehensive impacts along the life cycle of plastics, focusing not only on GHG emissions and energy consumption but also end-of-life impacts, such as littering potential, human toxicity, and aquatic ecotoxicity. To promote such research, national LCI database should be well established and developed to reduce any bias and ensure accuracy and applicability of assessment. Thailand has been developing its LCI database for 20 years: introducing life cycle thinking (since 1990), capacity building on human resources (since 2002), establishing the database and its master plan (since 2004), promoting its application (since 2010), improving data quality (since 2013), and developing a software (since 2015) (Gheewala, 2018).

Globally, studies have been conducted to better utilise LCA, especially to tackle the emerging marine plastic debris issue. As LCA was originally developed for impact assessment of land-based industries on mainly terrestrial and freshwater ecosystems, impact indicators for major drivers of marine ecology (i.e. sensitivity of marine biota with plastic debris at community and ecosystems scales) are less developed (Woods et al., 2016). To fill the gap, a specific framework to assess marine plastic debris impact was developed (Verones et al., 2020) (Figure 1). The framework considers three categories of plastic: macro (>5 mm), micro (<5 mm), and nano (<1 µm). Each category can end up in air, terrestrial, freshwater, or marine compartments, and possibly move between compartments. Different compartments will generate different exposure pathways and cause varied effects depending on the receptors. Nano-plastics could be toxic to humans if inhaled. Together with micro-plastics, nano-plastics could be ingested by invertebrates and vertebrates in terrestrial and freshwater compartments, which could be toxic to humans if they ingest such animals, create ecotoxicity, have physical effects on biota, and affect invasive species. In the marine compartment, macro-plastics are exposed through entanglement and accumulation that could disrupt socio-economic as well as natural and cultural values of tourism sites such as beaches, coral reefs, or landscapes. The framework clearly indicates the damaging impacts of marine plastic debris, not only on ecosystem quality but also on human health as well as on socio-economic and cultural values.

Figure 1. Framework for Marine Plastic Debris Assessment in LCA

Source: Verones et al. (2020).

Sonnemann (2018) highlighted the integration of holistic life cycle thinking into business practices. Current businesses create products based on the exclusive consideration of environmental impacts. For instance, businesses often end up choosing plastic bottles instead of steel cans or glass bottles for packaging, based on limited environmental indicators. Adopting the comprehensive LCA in the entire business will show the wider environmental impacts and a truly environment-friendly product. Vázquez-Rowe (2018) discussed the unmapped marine debris impacts during LCA of the marine ecosystem conducted by Langlois et al. (2014). Vázquez-Rowe (2018) mentioned the urgent need to consider micro-plastics impacts due to direct littering in the marine ecosystem, including human toxicity from seafood, ecosystem quality impacts on the different trophic levels such as seabirds, and loss of resources and revenue.

Such global efforts will inspire similar efforts to better utilise LCA in combatting marine plastic debris, especially in ASEAN countries. Such efforts will consider plastics in their entire life cycles in a more holistic way, rather than exclusively measuring the indicators of GHG emissions and energy consumption. Considering the damaging impacts of plastic on human health as well as on socio-economic and cultural values will enrich the state of understanding on the LCA of plastics. In the future, such holistic life cycle thinking will be applied to business at all levels.


References

Chemical Impacts of Plastics on the Marine Ecosystem

 

In 2015, global plastic production reached 322 million metric tonnes. Light, durable, and flexible, plastic has become popular over time due to its low production cost. With increased production and consumption of plastic, concerns about its effects on the marine environment started to emerge due to its long-term chemical stability in the oceans (Andrady and Rajapakse, 2017). Plastic in the oceans is fragmented into smaller pieces by UV radiation, which, in turn, are ingested by marine organisms, causing wounds, ulcerating sores, blockage of digestive systems, and, in extreme circumstances, ruptured bladders of marine species such as turtles. Ingestion of large amounts of plastic can create a false sense of fullness while slowing the rate of digestion (Ryan, 2016).

Three types of toxicity from plastic pose threats to the environment: additives mixed during processing and fabrication of products, residual monomers or catalysts trapped in the resin, and chemicals picked up by plastics from the environment. Of the three, additives are found to have the highest concentrations in plastic products. These include fillers, plasticisers, flame retardants, colorants, UV stabilisers, thermal stabilisers, and processing aids (Table 1).

Table 1. Types of Additives in Common Plastic

Class of additives

Functions

Examples

Fillers

Reinforcement; reduce cost

Clays, silica, glass, chalk, alumina, asbestos, rutile

Plasticisers

Soften polymer to make it flexible and extensible

Di-n-octyl phthalate, other phthalates

Flame retardants

Prevent ignition and/or flame propagation

Poly (bromo diphenyl ethers), alumina, phosphites

Colorants

Impart desired colour to product

Cadmium, chromium, lead, cobalt compounds

UV stabilisers

Control degradation of plastic regularly exposed to solar radiation

Hindered amine light stabilisers, benzo-phenone light-absorbing compounds

Thermal stabilisers

Control degradation during processing

Diakyl maleates, diakyl marcaptides

Processing aids

Ease processing of polymer

Waxes, oils, long-chain esters of polymeric alcohols

Others (anti-statics, biocides, odorants)

Obtain desired property in product

 

Source: Andrady and Rajapakse (2017).

Plastic in oceans retains additives, which are then directly transferred to marine organisms through prey ingestion. Indirect toxicity results when additives not chemically bound to the plastic are released into the environment and become available to organisms (Hermabessiere et al., 2017).

The most common additives found in marine debris are brominated flame retardants (BFRs) , phthalates, nonylphenols, bisphenol A (BPA), and antioxidants.

1. BFRs

Generally, BFRs are potential endocrine disruptors. Organisms exposed to endocrine disruptors will suffer in multiple developmental, reproductive, neurological, immune, and metabolic diseases (Ingre-Khans, Ågerstrand, and Rudén, 2017). BFRs are used in plastic products such as electronic devices and insulation foams to reduce flammability. The additives cover a range of chemicals, including the most commonly used additives in plastic industry, such as polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane, and tetrabromobisphenol A. Research shows that some types of BFRs are not chemically bound to polymer matrix, thus causing them to leach into the environment. Some commercial formulations of BFRs, called penta-, octa-, and deca-brominated diphenyl ethers (BDEs), are ubiquitous, harmful, stable, and bioaccumulate in the environment, with detrimental impacts on human health. Penta- and octa-BDEs have been banned in the European Union (EU) since 2004. The EU also banned deca-BDE for electronic and electrical applications in 2009 (European Commission, 2003; European Council Decision, 2009). Japan has  banned production and importation of tetra- and hepta-BDEs since 1995 (Covaci et al., 2008).

Besides being regulated under the European Council Decision in 2009, several types of BDEs have also been controlled by the Stockholm Convention since 2004. The convention prohibits persistent organic pollutants, which include deca-, hexa-, hepta-, tetra-, and penta-BDEs. Many countries in Southeast Asia and East Asia, including Japan, China, the Republic of Korea, Cambodia, Indonesia, the Lao People's Democratic Republic, Myanmar, the Philippines, Singapore, and Thailand, have ratified the convention (Stockholm Convention, 2019a). Under the regulation, deca-BDEs in plastic housing and parts used for heating home appliances are allowed at concentrations lower than 10% by weight (Stockholm Convention, 2019b). Although the convention does not set allowances for hexa-, hepta-, tetra-, and penta-BDEs, these have to be recycled through an environmentally sound mechanism, they are not allowed to be exported if their concentrations exceed the standard in the territory of the involved party, and their use must be under control of relevant stakeholders (Stockholm Convention, 2019c; Stockholm Convention, 2019d).

In 2003, the EU adopted the Restriction of Hazardous Substances (RoHS) Directive 2002/95/EC, which restricts the use of hazardous substances in electrical and electronic equipment. PBDEs are amongst the prohibited substances. The directive notes that PBDEs can be used only at 0.1% concentration by weight since they affect the endocrine system (RoHS Guide, 2020). Some Southeast Asian and East Asian countries have adopted a similar approach regarding PBDEs. For instance, China’s Requirements for Concentration Limits for Certain Restricted Substances in Electrical and Electronic Products SJ/T 11363-2006 states that PBDE concentration (deca-BDE not included) in products should not surpass 0.1% by weight. In general, China has regulations on PBDEs, such as the Ordinance on Management of Pollution and Control of Pollution from Electronic Information Products in 2007 and the Administrative Measures on Pollution Prevention of Waste from Electrical and Electronic Equipment in 2008 (revised in 2016) (Ni et al., 2012; Chem Safety Pro, 2019). Weak enforcement of those regulations, however, remains an issue (Ni et al., 2012). Viet Nam and Singapore allow the use of PBDEs with as much as 0.1% concentration by weight in electric or electronic products (Government of Viet Nam, 2011; Government of Singapore, 2020). As Thailand has no strong legal frameworks that control the use of PBDEs, they are found in some products, including electronics, furniture, and car seats. However, some types of BDEs (47, 99, 153, 175, and 183) will be added to the Thailand Hazardous Substances List, which is annexed to the Notification of Ministry of Industry on List of Hazardous Substances (No. 4) (Muenhor and Harrad, 2018). Malaysia also prohibits the use of PBDEs in parts of lighting equipment based on MS 2237:2009, which restricts certain hazardous substances in electrical and electronic devices (SCP Malaysia, 2014). In Indonesia, a recommendation on industrial waste management is still being formulated by the Ministry of Industry and the United Nations Development Programme. This recommendation will aim to reduce or eliminate substances, including PBDEs, that can endanger the environment (Pusat Penelitian Kimia LIPI, 2017).

2. Phthalates

Phthalates or phthalic acid esters (PAEs),  found mostly in polyvinyl chloride (PVC), are plasticisers that can take 10%–60% concentration by weight of PVC. Since these additives are not bounded to polymer matrix,  they can easily leach into the environment during their manufacture, use, and disposal. A big concern is that phthalates can serve as endocrine disruptors even in small concentrations (Hermabessiere et al., 2017). 

3. Bisphenol A (BPA)

As one of the most commonly and globally produced chemicals, BPA is primarily used as monomer of the main component of the lining of aluminium cans. Humans are exposed to BPA  once it is released from food and drink packaging. Like phthalates, BPA is a significant endocrine disruptor. Other types of bisphenol, including bisphenol B, F, and S, may also pose threats to the environment (Hermabessiere et al., 2017).

4. Nonylphenols (NPs)

NPs are widely used as antioxidants and plasticisers in plastic production. They leach out of plastic bottles. Effluents from wastewater treatment plants are also a major source of NPs. These additives disrupt the endocrine system and can have adverse impacts on human health and the environment. NPs are banned in the EU. NPs can be found in seafood, including oysters, mussels, and fish (Hermabessiere et al., 2017).

5. Antioxidants

Antioxidants help prevent ageing of plastic and delay oxidation but can leach out of plastic packaging and into food. The use of antioxidants in plastic can be harmful because they are oestrogen mimics (Hermabessiere et al., 2017). One of the classes of endocrine disruptors, an oestrogen mimic is an artificial hormone that biologically behaves as oestrogen but has a different chemical structure. Excessive amounts of estrogen in the marine environment can impact marine animals by delaying their sexual maturity, decreasing the size of male reproductive anatomy, and making eggs thinner (UWEC, 2020). 

These additives can be found in marine water, sediment, and microplastic. As the final stop of all wastewater, marine water receives huge volumes of additives. PBDEs, di (2-ethylexyl) phthalate (DEHP), and NP are mostly detected in marine water. Additives can also be found in sediments affected by anthropogenic discharge through wastewater, atmospheric deposition, and sewage sludge. Plastic additives are found in microplastics since they are added in the manufacture of polyethylene and polypropylene (Hermabessiere et al., 2017).

Several studies on the chemical impacts of plastic have been conducted in Southeast Asian and East Asian countries. A study in the Mekong River Delta in Viet Nam revealed PBDE contamination in catfish, posing risks to people who eat them. This study showed that runoffs from dumping sites during floods and rains are the possible drivers that bring additives to surrounding areas. In this case, municipal wastes in dumping sites, consisting of household goods and electrical equipment, might contain PBDEs. Research in informal e-waste recycling sites in Viet Nam found high PBDE contamination in surrounding sediment and in fish, particularly mud carp. This was attributed to the high level of PBDEs in plastic parts in obsolete electronic equipment in e-waste recycling sites. Liu et al (2011) discovered PBDE contamination in tissues of marine fish from the South China Sea, the Bohai Sea, the East China Sea, and the Yellow Sea, while Ilyas et al. (2013) indicated that a high level of PBDEs was observed in municipal dumpsites. Seabirds are also vulnerable to the impacts of chemicals in plastic. A study in the northern Pacific Ocean discovered oceanic seabirds ingesting plastic debris due to the growing amount of plastic entering the ocean. PBDEs were found in the abdominal adipose tissue of the species.


References

Leakage Estimation

 

Field researchers have undertaken several estimations to capture plastic leakage into the marine environment. Their results can differ depending on the scope and methodologies applied.

Land to Ocean Leakage

In 2010, Jambeck et al. (2015) estimated the leakage by calculating the amount of mismanaged plastic waste generated annually by populations living within 50 kilometres of a coast in 192 countries. The estimation framework included (1) annual waste generation per capita, (2) percentage of plastic waste, and (3) percentage of mismanaged plastic waste. The amount of mismanaged plastic waste was converted to the amount of marine plastic debris by applying a range of conversion rates.

Table 1 lists some countries that contributed the most leakage in 2010. Six Association of Southeast Asian (ASEAN) members (Indonesia, the Philippines, Viet Nam, Thailand, Malaysia, and Myanmar) were included in the top 20 countries. China topped the list. The global leakage estimation was 4.8 million–12.7 million metric tonnes/year (equivalent to 1.7%–4.6% of total plastic waste generated in those countries).

Table 1. Estimated Marine Plastic Debris Leakage in 2010

Rank

Country

Estimated Leakage in 2010 

(million metric tonnes/year)

 

Global (192 countries)

4.8–12.7

1

China

1.32–3.53

2

Indonesia

0.48–1.29

3

Philippines

0.28–0.75

4

Viet Nam

0.28–0.73

5

Sri Lanka

0.24–0.64

6

Thailand

0.15–0.41

7

Egypt

0.15–0.39

8

Malaysia

0.14–0.37

12

India

0.09–0.24

17

Myanmar

0.07–0.18

Source: Jambeck et al. (2015).

Land to River, Lake, and Ocean Leakage

Borrelle et al. (2020) update the annual amount of mismanaged plastic waste entering aquatic ecosystem (covering oceans, rivers, and lakes) from 2016 to 2030 in 173 countries. Applying a methodology similar to that of  Jambeck et al. (2015), the estimation integrates expected population growth, annual waste generation per capita, as well as proportion of plastic waste and mismanaged waste. Those variables were integrated using a distance-based probability function, considering the spatially explicit waste generation and downhill flow accumulation.

The leakage in 2016 becomes the baseline estimation (Table 2), while the leakage in 2030 is estimated for three scenarios: (1) business as usual, in which waste generation and plastic production follow current trajectories; (2) ambitious, which draws upon existing global commitments in reducing the leakage; and (3) target (<8 million metric tonnes), estimated in 2010 by Jambeck et al. (2015). Russia tops the list, while two East Asia countries (China and Japan) and five ASEAN countries (Indonesia, Thailand, the Philippines, Myanmar, and Viet Nam) are included in the top 20. Under the business-as-usual scenario, the global estimated leakage will reach up to 90 million metric tonnes/year by 2030.

Table 2. Estimated Aquatic Ecosystem Plastic Waste Leakage in 2016 and 2030

Rank in 2016

Country

Estimated Leakage in 2016

(million metric tonnes/year)

Estimated Leakage in 2030

(million metric tonnes/year)

Business as usual

Ambitious

Target

-

Global (173 countries)

19–23

35.8–90.0

19.8–53.3

3.4–12.0

1

Russia

2.99–3.40

4.72–10.46

1.32–5.43

0.02–2.63

2

India

2.51–3.21

4.74–13.93

2.50–7.28

0.49–1.42

3

Indonesia

1.55–1.83

2.83–6.42

2.04–4.71

0.40–0.90

4

China

1.41–1.74

2.46–7.12

2.03–5.87

0.04–0.11

5

Thailand

0.96–1.13

1.60–2.96

0.63–1.17

0.01–0.02

9

Philippines

0.46–0.52

0.88–2.48

0.49–1.37

0.10–0.27

11

Myanmar

0.33–0.39

0.61–1.39

0.47–1.13

0.23–0.54

15

Viet Nam

0.26–0.31

0.47–1.20

0.31–0.79

0.06–0.15

17

Japan

0.26–0.29

0.39–1.05

0.22–0.61

0.01–0.03

Source: Borrelle et al. (2020).

River to Ocean Leakage

Meijer et al. (2021) recently estimated that amongst 31,904 rivers in 163 countries, more than 1,500 rivers account for 80% of global plastic waste leakage. The global leakage of 0.8 million–2.7 million metric tonnes/year estimated by Meijer et al. (2021) is far below the amount estimated by Jambeck et al. (2015) in 2010. The reason behind the lower estimate is not the reduction of single-use plastics or the improvement of waste management systems but the estimation methodologies. In addition to common variables, such as population, waste generation per capita, and proportion of mismanaged waste, Meijer et al. (2021) utilised a probabilistic model that considered additional variables, including land use, terrain slope, wind, and precipitation. The model was then calibrated and validated against recent field observations from 2017 to 2020. Despite the difference, the results find that ASEAN countries remain as main contributors.

Table 3 lists five ASEAN countries as the top 10 contributors. Amongst these countries, the largest contributor is the Philippines, with seven rivers in the top 10 plastic-emitting rivers (Table 4), followed by Malaysia (3rd), Indonesia (5th), Myanmar (6th), Viet Nam (8th), and Thailand (10th).

Table 3. Recent Estimated Marine Plastic Leakage

Rank

Country

Recent Estimated Leakage

(million metric tonnes/year)

 

Global (163 countries)

0.8–2.7

1

Philippines

0.356

2

India

0.126

3

Malaysia

0.073

4

China

0.071

5

Indonesia

0.056

6

Myanmar

0.040

7

Brazil

0.038

8

Viet Nam

0.028

10

Thailand

0.023

Source: Meijer et al. (2021).

Table 4. Predicted Top 10 Plastic-Emitting Rivers

Rank

Catchment

Country

Recent Estimated Leakage

(million metric tonnes/year)

1

Pasig

Philippines

0.063

2

Tullahan

Philippines

0.013

3

Ulhas

India

0.013

4

Klang

Malaysia

0.013

5

Meycauayan

Philippines

0.012

6

Pampanga

Philippines

0.009

7

Libmanan

Philippines

0.007

8

Ganges

India

0.006

9

Rio Grande de Mindanao

Philippines

0.005

10

Agno

Philippines

0.005

Source: Meijer et al. (2021).

The results are consistent with Lebreton et al. (2017) and Schmidt et al. (2017), who found that 1.15 million–2.41 million metric tonnes and 0.41 million–4 million metric tonnes, respectively, of plastic flows from rivers to oceans annually. The top 20 polluting rivers were mostly in Asia (Table 5) and accounted for more than two-thirds (67%) of the global leakage (Lebreton et al., 2017). Amongst the top 20, seven rivers—Brantas (6th), Pasig (8th), Irrawaddy (9th), Solo (10th), Mekong (11th), Serayu (14th), and Progo River (19th)—are in ASEAN countries.

Table 5. Predicted Top 20 Polluting Rivers

Rank

Catchment

Country

Estimated Leakage

(million metric tonnes/year)

1

Yangtze

China

0.333

2

Ganges

India, Bangladesh

0.115

3

Xi

China

0.074

4

Huangpu

China

0.041

5

Cross

Nigeria, Cameroon

0.040

6

Brantas

Indonesia

0.039

7

Amazon

Brazil, Peru, Columbia, Ecuador

0.039

8

Pasig

Philippines

0.039

9

Irrawaddy

Myanmar

0.035

10

Solo

Indonesia

0.033

11

Mekong

Thailand, Cambodia, Lao People’s Democratic Republic, China, Myanmar, Viet Nam

0.023

12

Imo

Nigeria

0.022

13

Dong

China

0.019

14

Serayu

Indonesia

0.017

15

Magdalena

Colombia

0.017

16

Tamsui

Taiwan

0.015

17

Zhujiang

China

0.014

18

Hanjiang

China

0.013

19

Progo

Indonesia

0.013

20

Kwa Ibo

Nigeria

0.012

Source: Lebreton et al. (2017).

Using underlying mismanaged plastic waste data similar to that used by Lebreton et al. (2017), Schmidt et al. (2017) concluded that 10 rivers  (Table 6) account for 88%–95% of global leakage to the ocean. Eight out of the 10 rivers are in Asia, including the Mekong (10th), which flows through five ASEAN countries. The estimated leakage is higher because Schmidt et al. (2017) compiled a larger data set and treated microplastic and macroplastic separately. Reducing plastic leakage by 50% in the 10 top-ranked rivers would reduce total river-based leakage by 45%.

Table 6. Predicted Top 10 Polluting Rivers

Rank

Catchment

Country

Estimated Leakage

(million metric tonnes/year)

1

Yangtze

China

16.884

2

Indus

India, China, Pakistan

4.809

3

Huang He

China

4.099

4

Hai He

China

3.448

5

Nile

Egypt, Sudan, South Sudan, Ethiopia, Uganda, Congo, Kenya, Tanzania, Rwanda, Burundi

3.293

6

Meghna, Bramaputra, Ganges

Bangladesh, Bhutan, China, India, Nepal

3.017

7

Zhujiang

China, Viet Nam

2.515

8

Amur

Russia, China

2.087

9

Niger

Benin, Guinea, Mali, Niger, Nigeria

1.990

10

Mekong

Thailand, Cambodia, Lao PDR, China, Myanmar, Viet Nam

1.931

Source: Schmidt et al. (2017).

Recent estimation by Meijer et al. (2021) shows a significant increase of leakage from several rivers in the Philippines, compared with the estimation by Lebreton et al. (2017). For instance, the amount of leakage from the Pasig River increases more than 60%, from only 0.039 million metric tonnes/year in 2017 (Table 5). Rivers in ASEAN countries, especially in the Philippines, have toppled rivers in China from the top spot as emitters of plastic to oceans since Meijer et al. (2021) considered spatial variability of the amount of mismanaged plastic waste within a river basin and utilised climate and terrain characteristics to differentiate the probability of leakage. With these assumptions, relatively small river basins, including those in ASEAN countries (e.g. the rivers in the Philippines), contribute proportionally more leakage than larger river basins, where the amount of mismanaged plastic waste is similar but located further upstream. Meijer et al. (2021) answer the limitation on Lebreton et al. (2017) and Schmidt et al. (2017), who overestimated the leakage from large rivers and underestimated the leakage from smaller rivers due to the exclusion of those important assumptions. The trend is a backstep and a warning that the region must reduce marine plastic debris.

Harmonised Methodology to Support Effective Countermeasures

Although several estimations have been undertaken to capture plastic leakage into the marine environment, more data should be estimated periodically. The results of estimations differ from one another depending on the scope and methodologies applied. To avoid any underestimation, harmonising the estimation methodologies is important. With harmonised methodology, data can be compared and validated against each other. Using a larger set of data, as done by Schmidt et al. (2017) and Borrelle et al. (2020), will further increase estimations’ accuracy. However, some countries might not have country-specific data, so that the data estimated using a proxy value with some assumptions and a certain level of uncertainties might lead to underestimation. For instance, Schmidt et al. (2017) extended by 41 countries the estimation of Jambeck et al. (2015) of mismanaged plastic waste generation rate from 192 coastal countries. The waste generation rate and plastic composition for these 41 countries were taken from Hoornweg and Bhada-Tata (2012) based on past regional estimation, while the mismanaged plastic waste was calculated based on average values for each World Bank economic classification (high income, upper middle income, lower middle income, or low income). In most developing countries, including India (Nandy et al., 2015), where plastic waste is mostly recovered by the informal sector, a significant amount of plastic waste is excluded in such estimation.

To address this issue, government shall support such research by monitoring leakage in rivers and providing valid waste management data regularly. The lack of actual waste management data, especially in ASEAN countries, might lead to lower or higher leakage estimations, depending on the proxy data. The lower estimation by Meijer et al. (2021) does not necessarily mean the reduction of leakage. By utilising the appropriate harmonised methodology and supported by valid data from the respective governments, various policies can be formulated and/or evaluated to create effective countermeasures against marine plastic leakage.


References

    Borrelle, S.B., J. Ringma, K.L. Law, C.C. Monnahan, L. Lebreton, A. McGivern, E. Murphy, J. Jambeck, G.H. Leonard, M.A. Hilleary, M. Eriksen, H.P. Possingham, H. De Frond, L.R. Gerber, B. Polidoro, A. Tahir, M. Bernard, N. Mallos, M. Barnes, and C.M. Rochman (2020), ‘Predicted Growth in Plastic Waste Exceeds Efforts to Mitigate Plastic Pollution’, Science, 369, pp.1515–8. https://doi.org/10.1126/science.aba3656

    Hoornweg, D. and P. Bhada-Tata (2012), What a Waste: A Global Review of Solid Waste Management. World Bank, Washington, DC. https://openknowledge.worldbank.org/handle/10986/17388 (accessed 6 September 2021).

    Jambeck, J.R., R. Geyer, C. Wilcox, T.R. Siegler, M. Perryman, A. Andrady, R. Narayan, and K.L. Law (2015), ‘Plastic waste inputs from land into the ocean,’ Science, 347, pp.768–71. https://doi.org/10.1126/science.1260352

    Lebreton, L., J. van der Zwet, J.W. Damsteeg, B. Slat, A. Andrady, and J. Reisser (2017), ‘River Plastic Emissions to the World’s Oceans’, Nature Communications, 8, pp.15611. https://doi.org/10.1038/ncomms15611

    Meijer, L.J.J., T. van Emmerik, R. van der Ent, C. Schmidt, and L. Lebreton (2021), ‘More Than 1000 Rivers Account for 80% of Global Riverine Plastic Emissions into the Ocean’, Science Advances, 7, pp.eaaz5803. https://doi.org/10.1126/sciadv.aaz5803

    Nandy, B., G. Sharma, S. Garg, S. Kumari, T. George, Y. Sunanda, and B. Sinha (2015), ‘Recovery of consumer waste in India – A mass flow analysis for paper, plastic and glass and the contribution of households and the informal sector’, Resources, Conservation and Recycling, 101, pp.167–81. https://doi.org/10.1016/j.resconrec.2015.05.012

    Schmidt, C., T. Krauth, and S. Wagner (2017), ‘Export of plastic debris by rivers into the sea’, Environmental Science & Technology, 51, pp.12246–53. https://doi.org/10.1021/acs.est.7b02368

Material Flow Analysis for Plastics

 

Material flow analysis (MFA) is a quantitative method to figure out the flow of materials and energy through economy. MFA works by capturing mass balance in an economy, where extraction and import can be considered as inputs and consumption and export as outputs. The mass balance of inputs should be equal to outputs, which is useful in determining the efficiency of the use of material resources. From the perspective of waste in general, MFA is required to develop a standard tool of waste statistics between countries. However, it can be difficult to implement for plastic waste because many plastic materials, such as polyethylene and polypropylene, are used for different products (Moriguchi and Hashimoto, 2016).

MFA of Plastics in Thailand

Bureecaam, Chaisomphob, and Sungsomboon (2018) demonstrate the MFA for plastic waste and plastic waste management in Thailand. They use primary and secondary sources to obtain the data from 11 provinces.

Diagram, schematic

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Figure 1. MFA of Plastic in Thailand in 2013 (Source: Bureecaam et al., 2018). 

Figure 1 shows that the petrochemical industries in Thailand produced 7,827,481 tonnes of raw materials in 2013, around 1,101,329 tonnes of which were derived from recycled materials. After 2,732,675 tonnes were consumed, the generated plastic wastes were 3,560,595 tonnes. Some of the plastic wastes were then collected and disposed of by the local government, whilst 499,295 tonnes remained uncollected.  The collected plastic waste went to different treatment facilities, 765,883 tonnes of which were recycled while 220,949 tonnes of plastic waste were incinerated to generate energy. The remaining 1,986,648 tonnes of plastic waste were disposed of to a landfill site. Unfortunately, 597,115 tonnes of plastic waste were improperly managed in the collection and transportation process. The waste was then mixed with the uncollected waste in the previous process, resulting in 1,076,410 tonnes of plastic waste that ended up in the open environment, which potentially leaked into the oceans.

MFA of Plastics in the Philippines

MFA for plastic scraps in the Philippines is shown in Figure 2.

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Figure 2. MFA of Plastic Scraps in the Philippines (Source: Japan International Cooperation Agency, 2008). 

The Philippines produces 1,013,242 tonnes of plastic per year that are derived from three sources: imported resins (581,639 tonnes/year) and imported plastic waste (14,841 tonnes/year), local supply of recycled plastic (288,000 tonnes/year), and from local production of virgin raw material (128,762 tonnes/year). The number of total plastic products is then calculated by adding total plastic production and import of plastic finished product (344,493 tonnes/year) or 1,357,735 tonnes/year. To obtain the total local consumption, this number is deducted from the number of exported plastic finished product (96,330 tonnes/year), thus 1,261,405 tonnes/year.

Local consumption of plastics is processed in different phases: recycled, kept (still being used), and disposed of to landfill. Recycled plastic accounts for 243,267 tonnes/year. Those still being used and those disposed of to landfill account for 574,309 tonnes/year and 399,096 tonnes/year, respectively (Japan International Cooperation Agency, 2008).  Unfortunately, the study of MFA in the Philippines does not calculate the amount of unmanaged plastic waste that ends up in the open environment and could leak into oceans.  

MFA of Plastics in Malaysia

Malaysia’s plastic inventory was calculated based on a survey study, which showed 587,062 tonnes of local production of plastic products. Added to the 170,248 tonnes of imported plastic products, the amount of total plastic products was 733,828 tonnes. Local consumption of plastics was 511,697 tonnes, whilst exports were 222,131 tonnes. Of local plastic consumption, 47,843 tonnes were recycled whilst the rest (463,854 tonnes) went to final disposal. This study does not cover the amount of plastic waste that ended up in the open environment. Details of MFA plastics in Malaysia are shown in Figure 3.