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In 2019, the Government of Thailand released the and is developing the National Action Plan on Marine Plastic Debris to alleviate the current impacts and avert future damage caused by marine plastic debris. While these efforts are critical steps toward reining in the country¡¯s plastic pollution problem, further insight is needed into where the plastic waste comes from and how it moves in the environment.

This study presents the first large-scale assessment in Thailand to integrate national waste generation and waste management performance data with actual hydrological conditions to estimate how mismanaged plastic waste is carried and discharged into the marine environment. It aims to better understand how plastic waste travels from land-based sources to the marine environment by analyzing the material flow of plastic waste in five high-priority catchments (Phetchaburi, Mae Klong, Tha Chin, Chao Phraya and Bang Pakong) and three tourist hotspots (Krabi, Phuket and Ko Samui).

By mapping the relationship between waste sources, leakage pathways, and plastic discharges to the marine environment, this study identifies the most significant hotspots contributing to marine plastic debris and the specific associated waste handling practices (e.g., open dumpsites, household disposal behavior, etc.). Building on previous analysis on the material flow of plastics in Thailand and using the best available data from national sources, this study helps inform policy interventions and investments from the Government of Thailand and local administrative organizations to effectively reduce marine plastic debris. The models developed can also help monitor progress relative to environmental factors, such as seasonal rainfall variations.

KEY FINDINGS: HIGH-PRIORITY CATCHMENTS

• Despite a high municipal solid waste collection and recycling rate of 88.8% in Thailand, remaining uncollected plastic waste and many unsanitary disposal facilities result in an estimated 428 kton/year of mismanaged plastic waste.
• Most mismanaged plastic waste that is available for wash-off to rivers and the marine environment (defined as ¡®exposed mismanaged plastic waste¡¯) is generated in rural areas (70.1%) which have lower collection rates and contain the most disposal facilities,  A large amount of uncollected waste in the Chao Phraya catchment is disposed directly into waterways.
• 10 districts (of 247 in total) account for 51.7% of the total exposed mismanaged plastic waste in the high-priority catchments. These are all situated in or near Bangkok and are relatively close to the marine environment.
• Across four high-priority catchments (excluding Mae Klong), on average, 47.6% of mismanaged waste that ends up in the rivers is discharged into the marine environment.
• An annual average total of 9.3 kton/year of plastic waste is discharged into the marine environment from four high priority catchments (see figure below; numbers are excluding Mae Klong).
  • This is equivalent to a marine plastic footprint of 0.4 kg/capita/year.
  • During particularly rainy years this may increase to 14.3 kton/year, while it may be as low as 4.9 kton/year in drier years.

KEY FINDINGS: TOURIST HOTSPOTS

• A total of 16.8 kton/year of mismanaged plastic waste is generated, with the source varying across the tourist hotspots.
• There is an estimated 0.7 kton/year of exposed mismanaged plastic waste which is leaked into the environment primarily from unsanitary disposal facilities in cities and from uncollected waste in the more rural areas.
• The lack of reliable hydrological data in the tourist hotspots resulted in unreliable results for the transport of exposed mismanaged plastic waste to the marine environment.

RECOMMENDATIONS

Goal 1: Reduce transport of leaked mismanaged plastic waste (downstream in waste chain)

Initially, focus on areas at close distance from the coast that have been identified as key contributing districts:

• In urban areas: Install trash racks in urban drainage systems, just before the outlet to a main river or waterway, and clean them daily.
• In rural areas: Install trash racks in irrigation canals just downstream from villages.
• In rivers: Promote and expand river clean-up initiatives such as the one managed by the Bangkok Metropolitan Administration in the Chao Phraya River.
• Monitor plastic waste in the riverine environment as it is intercepted by trash racks.

Goal 2:  Reduce mismanaged plastic waste generation (mid-stream in waste chain)

• In urban areas: Further improve waste collection, particularly in the Chao Phraya catchment.
• In rural areas: Develop an efficient and coordinated waste collection system in rural Thailand.
• Invest in well-managed final disposal facilities and upgrade unsanitary disposal facilities (open dumpsites and controlled dumps), giving priority to the facilities nearby waterways, at close distance to the coast and in key districts.
• Consider introducing city-wide clean-up sweeps just before the start of the rainy season
• Improve laws and regulations to support the implementation of measures, including enforcing separation at source, monitoring and controlling the operation of waste disposal, and capacity building of local authority staff in waste management.

Goal 3: Improve the data and underlying models

• Increase systematic sampling of solid waste generation and composition at the Local Administrative Organization (LAO) or subdistrict levels. Require a daily log at disposal facilities of how much solid waste arrives at the facility and where each truck comes from.
• Include a specific solid waste management question in the National Statistical Office (NSO) annual survey module.
• Require recycling shops to provide a detailed overview of the amounts of the various types of waste that arrive at the locations and their individual recycling rate.
• Once better solid waste management data is available, the modelling can be further improved in the future by collecting hydrological data.

This study was conducted by a team from Deltares, Panya Consultants Co. Ltd., and HII and builds on methodology developed for a similar study in Indonesia. The study benefited from the inputs of various national stakeholders; extensive dialogue and inputs were provided by the Department of Marine and Coastal Resources and the Pollution Control Department in the Ministry of Natural Resources and Environment, Thailand. Funding for the study was provided by PROBLUE, an umbrella multi-donor trust fund, administered by the World Bank, that supports the sustainable and integrated development of marine and coastal resources in healthy oceans.