Marine Litter and Plastics Accounting

TG-6.12 Section 6: Thematic Methodologies Applied Draft

Circular ID	TG-6.12
Version	7.0
Badge	Applied
Status	Draft
Last Updated	May 2026

1. Outcome

1This Circular provides guidance on establishing stock-flow accounts for marine litter and plastics within the Ocean Accounts framework. Upon completing this Circular, readers will understand how to:

• 2categorise marine litter by material type and source
• 3compile flow accounts tracking litter from land-based and maritime sources to the marine environment
• 4develop stock accounts for accumulated litter in coastal zones, surface waters, the water column, and the seafloor
• 5attribute litter flows to economic sectors and geographic sources
• 6align marine litter accounts with SDG Target 14.1 indicators on marine pollution
• 7derive circular economy indicators linking litter accounts to plastics reduction targets under emerging international frameworks
• 8compile material flow accounts for synthetic materials from production through disposal to marine leakage

9The accounts compiled using this guidance support derivation of indicators for environmental pressure assessment in TG-2.7 Pollution Flows, contribute to assessment of residual flows from economy to environment in TG-3.4 Flows from Economy to Environment, inform circular economy indicators in TG-2.11 Resource Efficiency, and support reporting to the multilateral environmental agreements described in TG-2.10 MEA Indicators. Marine litter accounting also complements maritime transport activity accounts in TG-6.10 Maritime Transport where vessel-sourced litter is concerned.

2. Requirements

1This Circular requires familiarity with:

• 2

  TG-0.1 General Introduction — foundational Ocean Accounts components and SIDS-specific considerations relevant to marine litter accounting in small island contexts.

• 3

  TG-3.4 Flows from Economy to Environment — residual flow accounting, solid waste accounts, and attribution of emissions and waste to economic sectors, which underpins the marine litter flow accounting approach in Section 3.3.

3. Guidance Material

1Marine litter is defined as any persistent, manufactured or processed solid material discarded, disposed of, or abandoned in the marine and coastal environment. It constitutes one of the most visible forms of marine pollution¹. Plastics are the dominant material category, accounting for approximately 80 percent of all marine debris by count².

2SDG Target 14.1 (preventing and reducing marine pollution) provides the primary policy anchor for this Circular³. SDG indicator 14.1.1 specifically includes “floating plastic debris density” as a component of the index of coastal eutrophication and plastic debris density⁴. An INC process to develop a legally binding instrument on plastic pollution (UNEA Resolution 5/14, March 2022) is ongoing. Compilers should consult the UNEP INC website for current treaty status and emerging reporting obligations⁵⁶.

3Scope — microplastics. Microplastics (plastic particles less than 5mm in diameter, whether primary or secondary) are out of scope of this Circular. Detailed accounting for microplastic flows, stocks, and fragmentation is deferred pending further methodological development. This Circular addresses macroplastics (>25mm) and mesoplastics (5-25mm) only. Inline references to microplastics in the pathway descriptions are retained for completeness but are flagged as out-of-scope inputs that compilers should not attempt to quantify under this guidance. Countries developing experimental microplastic accounts should document methods separately and treat results as supplementary information.

4The SEEA CF physical supply and use table structure for solid waste records waste generation by economic sector and tracks flows to collection, treatment, and disposal destinations⁷⁸. For marine litter accounting, this framework is extended to capture waste that escapes management systems and enters the marine environment, as well as litter generated directly by maritime activities. General solid waste accounting structure follows TG-3.4 Flows from Economy to Environment.

3.1 Decision Use Cases and Upward Connections

Plastics treaty reporting and compliance monitoring

1Marine litter accounts link plastics material flow accounts (tracking production and use) to waste management accounts (tracking collection and disposal) to residual flow accounts (tracking marine leakage). This linkage eliminates redundant data collection across reporting obligations and keeps national waste statistics and international environmental monitoring consistent with one another.

Circular economy metrics for plastics

1Marine litter accounts quantify the proportion of plastic waste that escapes collection and treatment systems, providing the “leakage rate” indicator central to circular economy assessment. SEEA CF paras 3.268-3.278 establish the applicable residual flow framework⁹. These indicators feed directly into TG-2.11 Resource Efficiency.

Beach and ocean cleanup investment justification

1Stock accounts by environmental compartment (beach, floating, benthic) provide baseline estimates of litter volumes requiring removal. Flow accounts by source category enable prioritisation of interventions targeting high-contribution pathways. Time-series accounts tracking stock changes before and after cleanup programmes provide the quantitative basis for return-on-investment assessment. This use case links to environmental protection expenditure accounts addressed in TG-3.7 Governance Accounts.

Upward connections to indicator frameworks

• 1SDG 14.1.1 (Marine pollution) — directly supplies floating plastic debris density component¹⁰
• 2Pollution pressure indicators (TG-2.7) — provides physical flow data for litter generation intensity, mismanaged waste rates, and marine leakage indicators
• 3Circular economy indicators (TG-2.11) — enables calculation of recycling rates, waste utilisation rates, and decoupling factors
• 4MEA reporting (TG-2.10) — supports Kunming-Montreal Global Biodiversity Framework Target 2 and UNFCCC reporting

5The combined presentations approach in TG-3.8 Combined Presentations provides methods for integrating marine litter account data with economic and ecosystem condition accounts.

3.2 Marine Litter Framework: Categories, Sources, and Pathways

Material categories

1Plastics — the dominant component, requiring disaggregation by:

• 2Polymer type (polyethylene, polypropylene, polystyrene, PET, PVC, other polymers)
• 3Product category (packaging, single-use items, fishing gear, consumer goods, industrial materials)
• 4Size class (macroplastics >25mm, mesoplastics 5-25mm, microplastics <5mm)

5Bioplastics and materials marketed as biodegradable warrant careful treatment. Many do not degrade under marine conditions and should be accounted equivalently to conventional plastics. For materials with certified marine biodegradability (per ISO 18830:2016 and ISO 19679:2016 or equivalent), compilers may apply a degradation rate in the stock account’s outflow rows rather than treating the material as persistent. ISO 18830 and ISO 19679 certify aerobic biodegradation potential under controlled laboratory conditions and do not directly yield field rate constants. Compilers wishing to apply a degradation outflow should derive a first-order rate constant from field studies, document the temperature, UV, and turbulence assumptions applicable to the accounting area, and record the mass outflow in a dedicated “Certified biodegradation” row separate from the general “Degradation” row. Where certified degradation rates are unavailable, conservative practice treats all plastics as persistent.

6Other materials — including glass and ceramics, metal, rubber, textiles, paper and cardboard, processed wood, and other manufactured materials.

7The GESAMP Guidelines for the monitoring and assessment of plastic litter in the ocean provide a harmonised categorisation framework¹¹. The European Waste Catalogue (EWC-Stat) offers additional detail for waste source identification¹².

Source categories

1Land-based sources — estimated to contribute approximately 80 percent of marine litter globally (Jambeck et al. 2015), including municipal solid waste, industrial and manufacturing residues, construction and demolition waste, agricultural plastics, sewage-related debris, coastal tourism and recreation waste, and riverine transport from inland areas.

2Sea-based sources — including: fishing activities (abandoned, lost, or discarded fishing gear — ALDFG); shipping (cargo loss, operational waste); offshore energy operations; aquaculture (equipment, floats, feed bags); recreational boating; and maritime structures and port operations.

3The relative contribution of different sources varies by location. SIDS may have higher proportionate contributions from sea-based sources. See SIDS-specific considerations in TG-0.1 General Introduction¹³.

Pathways to the marine environment

Pathway	Description
Direct coastal input	Waste deposited, blown, or washed directly from coastal zones into the sea.
Riverine transport	Waste carried by rivers from upstream sources; rivers are major conduits for land-based marine litter14.
Stormwater and urban runoff	Waste transported through drainage systems during precipitation events.
Wastewater discharge	Microplastics and other debris not removed during wastewater treatment.
Atmospheric transport	Lightweight items and microplastics transported by wind.
Direct disposal at sea	Deliberate dumping (regulated under the London Convention and Protocol)15.
Accidental loss at sea	Cargo loss, equipment failure, vessel incidents.

1The SEEA CF notes that controlled landfills are within the economy, whilst uncontrolled disposal to the environment represents a residual flow¹⁶. For marine litter accounting, waste reaching marine waters represents a flow to the environment recorded in residual flow accounts.

2The diagram below is provided in two equivalent forms: an interactive Observable rendering for the GOAP web portal, and a Mermaid flowchart fallback that renders correctly in static PDF and print exports.

flowchart TB
  managed["Managed waste<br/>(economy)"]
  mismanaged["Mismanaged waste"]
  land["Land-based<br/>accumulation"]
  riverine["Riverine &<br/>stormwater transport"]
  coastal["Coastal stock<br/>(beaches, shoreline)"]
  floating["Floating stock<br/>(surface, water column)"]
  benthic["Benthic stock<br/>(seafloor)"]
  fragmentation["Fragmentation<br/>(macro to micro)"]
  degradation["Degradation<br/>& mineralisation"]
  seabased["Sea-based sources<br/>(ALDFG, shipping)"]

  managed -->|leakage| mismanaged
  mismanaged -->|uncontrolled disposal| land
  mismanaged -->|runoff & drainage| riverine
  land -.->|wash-off| riverine
  land -->|direct coastal input| coastal
  riverine -->|river mouth deposition| coastal
  riverine -->|riverine discharge| floating
  seabased -->|at-sea loss| floating
  seabased -.->|sinking gear & cargo| benthic
  coastal <-->|wave action & tides| floating
  floating -->|sinking| benthic
  floating -.->|beaching| coastal
  coastal -.->|UV & abrasion| fragmentation
  floating -.->|UV & wave action| fragmentation
  fragmentation -.->|over time| degradation

3Figure 6.12.1 summarises marine litter stock-flow relationships (see also TG-3.4 Section 3.2).

Figure 6.12.1 Marine solid-plastic residual flows from managed and mismanaged sources through coastal, floating, and benthic stocks toward microplastics. Dashed edges = conditional/episodic paths; double arrow = coastal↔floating exchange; microplastics terminal muted (out of scope). Stocks non-summable. Scope: Escape residuals only; economy-side waste SUT out of scope -- TG-3.4. Source: TG-6.12 (marine solid plastic waste accounting framework); SEEA CF 2012, Chapter 3 (residual flows and waste treatment); UNEP/GESAMP 2021 (Sources, Fate and Effects of Microplastics in the Marine Environment, Pt. 2), paras. 2.1--2.4.

3.3 Flow Accounting: Litter Inputs to the Marine Environment

1Flow accounts record the quantity of litter entering the marine environment during an accounting period, measured in mass units (tonnes) or, for monitoring purposes, item counts.

Land-based source flows

1Land-based litter flows require estimation of:

• 2Mismanaged waste — waste not formally collected or improperly disposed after collection
• 3Leakage rates — the proportion of mismanaged waste that reaches marine waters (dependent on proximity to coast, hydrological connectivity, and waste characteristics)

4The methodology developed by Jambeck et al. (2015) estimates plastic waste input from land to ocean based on coastal population, waste generation rates, waste management infrastructure, and modelled leakage¹⁷:

Plastic marine debris = Coastal population ×
                        Waste generation rate ×
                        Plastic content of waste ×
                        Inadequately managed waste share ×
                        Leakage factor to ocean

5Lau et al. (2020) extended this framework for scenario analysis of waste management interventions and material substitution¹⁸. Borrelle et al. (2020) projected plastic waste growth trajectories¹⁹.

6For ocean accounting purposes, this estimation approach should be disaggregated by economic sector where possible, geographically referenced to identify priority coastal areas, and time-series consistent to track trends.

7The SEEA CF physical supply and use table for solid waste provides the structural framework²⁰:

Flow Category	Physical Unit	Recording
Waste generation by industry	Tonnes	Supply table, by ISIC class
Waste generation by households	Tonnes	Supply table, household sector
Waste collected	Tonnes	Use table, waste management industry
Waste to controlled disposal	Tonnes	Use table, controlled landfill/incineration
Waste to environment	Tonnes	Use table, environment (residual flow)

8For marine-specific accounting, “waste to environment” is disaggregated to distinguish:

• 9Waste to marine and coastal waters
• 10Waste to inland waters (with subsequent marine pathway)
• 11Waste to land (coastal littering, beach deposits)

Maritime source flows

1Fishing gear losses — ALDFG estimation uses fishing and aquaculture activity data from TG-6.7 and TG-6.8. Abandoned, lost, or discarded fishing gear is estimated at 5.7 percent of fishing nets, 8.6 percent of traps, and 29 percent of fishing lines lost globally each year²¹. These global average rates may not reflect conditions in artisanal fisheries. Compilers should apply gear-specific and fishery-specific loss rates where available from national or regional fisheries management organisations²². Accounting requires data on fishing fleet composition, gear types, estimated loss rates, and conversion to mass units.

2Vessel operational waste — MARPOL Annex V regulates discharge of garbage from ships²³. Accounting draws on port reception facility records, MARPOL incident reporting, and vessel surveys.

3Offshore operations — Waste from offshore energy platforms, aquaculture installations, and maritime structures. Cross-reference to TG-6.9 Offshore Energy for offshore accounting context.

4Cargo losses — Container losses and other cargo overboard incidents, reported under maritime incident databases.

Riverine inputs

1Rivers transport substantial quantities of litter from inland areas to the marine environment, with a small number of rivers contributing a disproportionate share of global riverine plastic input²⁴. Accounting requires:

• 2Monitoring of litter concentrations in river outflows
• 3Estimation of total transport based on flow volumes
• 4Attribution to upstream catchment sources where possible

5For national ocean accounts, riverine inputs represent the cumulative effect of upstream waste management and should be linked to inland waste generation and management accounts. Hydrological data used for water flow accounting may serve as a basis for estimating litter transport volumes where direct litter monitoring data are limited.

3.4 Stock Accounting: Marine Litter Accumulation

1Stock accounts record the quantity of litter accumulated in the marine environment at the opening and closing of an accounting period. The following template provides a compilation framework.

2Table 3.4.1: Marine litter physical stock-flow account (tonnes)

Entry	Floating	Beach	Seabed	Water Column	Total
Opening stock	850	1,240	3,100	420	5,610
Inflows
Land-based input (rivers)	180	—	—	—	180
Land-based input (direct coastal)	—	95	—	—	95
Sea-based input (shipping, fishing)	45	—	12	—	57
Import via ocean transport (transboundary)	0	0	0	0	0
Transfer from other compartment	25	110	65	15	215
Total inflows	250	205	77	15	547
Outflows
Collection/removal	—	140	—	—	140
Degradation	12	8	5	3	28
Transfer to other compartment	135	65	—	15	215
Export (currents)	25	—	—	—	25
Total outflows	172	213	5	18	408
Closing stock	928	1,232	3,172	417	5,749

3The “primary entry” notation indicates the compartment where each source type is first recorded. Subsequent redistribution is captured through transfer rows. Inter-compartment transfers balance: total outflows as transfers (215 tonnes) equal total inflows from transfers (215 tonnes), maintaining mass conservation. Column arithmetic: for each compartment, opening stock + total inflows - total outflows = closing stock. The “import via ocean transport” row records transboundary litter flows arriving via ocean currents. Receiving-coastline countries (e.g., Pacific island states in North Pacific Gyre currents) should populate this row to distinguish externally-sourced accumulation from domestic inputs (see Section 3.5).

4Note on terminal sinks: The seabed compartment is treated as a terminal sink, with no resuspension or redistribution from seabed to other compartments recorded. Where monitoring data indicate significant resuspension (e.g., in high-energy shallow-water environments), compilers should add a transfer outflow row for the seabed compartment and a corresponding inflow row for the water column.

Beach and coastal stocks

1Beach litter is the most accessible stock for monitoring, with established survey methodologies²⁵. Stock accounts record mass or item counts per unit area (beach length, surface area), aggregated to total coastal stock and disaggregated by material category.

2Beach stock accounts recognise that beaches are dynamic interfaces:

• 3New litter deposits during each tidal cycle and storm event
• 4Removal occurs through clean-up activities, burial, and resuspension
• 5Opening and closing stocks relate through: Closing stock = Opening stock + Deposits - Removals - Degradation

6Clean-up activities should be recorded as economic flows (environmental protection expenditure under CEPA 3) and their effect on beach stocks quantified²⁶. This links to environmental expenditure accounts in TG-3.7 Governance Accounts.

Floating litter stocks

1Surface and near-surface floating litter is measured through visual surveys, net tows, or remote sensing. SDG indicator 14.1.1 specifies floating plastic debris density as a monitoring parameter²⁷. Stock accounts for floating litter face specific challenges:

• 2Dynamic distribution influenced by currents, winds, and convergence zones
• 3Variable vertical distribution (surface to depth)
• 4Difficulty in scaling point observations to total stock estimates

5Global accumulation zones (ocean gyres) represent areas of elevated floating debris concentration. Stock accounts may record density estimates (items or mass per km2) for defined ocean areas, total estimated stock based on density and area, and uncertainty ranges. Litter density may also serve as an ecosystem condition indicator. The relationship between accumulation and ecosystem condition is addressed in TG-2.1 Biophysical Indicators.

Water column stocks

1Litter suspended in the water column is less well characterised than surface or benthic stocks. Accounting approaches are necessarily more experimental and may rely on depth-stratified sampling data, modelled vertical distribution based on particle characteristics, or extrapolation from limited survey data.

Seafloor stocks

1Benthic litter accumulates on the seabed, particularly in areas of high sedimentation, submarine canyons, and deep-sea plains. Monitoring uses trawl surveys, remotely operated vehicle (ROV) transects, and baited camera systems. Stock accounts should record density by seabed type and depth zone, estimated total stock within national waters, and composition by material category. The SEEA EA addresses ecosystem condition, including pollutant presence as a condition variable²⁸.

3.5 Source Attribution and Material Flow Accounts

1Effective marine litter policy requires attribution of litter to the economic units and locations responsible for its generation. The SEEA CF principle of recording residual flows by source industry applies²⁹.

Industry source attribution

1Industry sources of marine litter, classified by ISIC:

Sector	ISIC	Marine litter nexus
Plastic resin/product manufacture	20, 22	Production waste, pellet losses
Food, beverage, tobacco	10-12	Packaging waste
Textiles and apparel	13-14	Microfibre release
Marine fishing	0311	Fishing gear losses, operational waste
Marine aquaculture	0321	Equipment losses, feed bags
Water transport	50	Vessel waste, cargo losses
Accommodation and food service	55-56	Disposable items, packaging
Waste management	38	Leakage from collection and disposal

2Where direct industry-level data on marine litter contributions are unavailable, compilers may use waste composition data from beach litter surveys to attribute litter to source industries through product-to-industry concordances. For example, packaging items in beach surveys can be mapped to the manufacturing industry that produced them (ISIC 10-12 for food packaging) and to the retail or hospitality industry that distributed them (ISIC 47, 55-56). Detailed guidance on industry classification is in TG-3.3 Economic Activity.

Household source attribution

1Households are major sources of marine litter through consumer product disposal, littering, inadequate waste storage, and microplastic releases (laundry, personal care products). Household marine litter is recorded in the household sector column of the physical supply table.

Geographic allocation

1Coastal zone delineation — Coastal zone definitions should align with administrative boundaries whilst recognising functional connectivity to marine waters³⁰. See TG-1.2 Marine Spatial Planning.

2Catchment-based accounting — River catchments as accounting units enable tracking of riverine litter pathways.

3Maritime zone accounting — Recording of sea-based source litter by location (territorial sea, EEZ, high seas) supports jurisdictional analysis.

4Transboundary litter flows. Litter originating in foreign jurisdictions and transported by ocean currents should be recorded separately in physical flow accounts using the “import via ocean transport” row in Table 3.4.1. Failure to do so will distort domestic source attribution. The three principal estimation approaches are: (a) ocean debris transport modelling (using circulation models to back-calculate probable source regions); (b) source-marker or polymer-signature analysis (comparing polymer types and additive profiles to known source regions); and (c) branded-product origin analysis from beach surveys. Each approach carries substantial uncertainty, so transboundary import estimates should always be reported with a sensitivity range and a method tag. Attribution of transboundary litter to source countries requires international coordination through regional seas conventions (e.g., SPREP for the Pacific)³¹. For SDG 14.1.1 reporting, domestic source attribution takes precedence, and transboundary flows should be reported as supplementary information.

5The SEEA CF supports sub-national disaggregation where data permit³². Priority geographic units include coastal municipalities, river catchments with marine outlets, port areas and shipping lanes, and marine protected areas.

3.6 Material Flow Account for Synthetic Marine Litter: Worked Example

1This section presents a worked example tracking plastics from production through consumption, waste generation, collection and treatment, to marine leakage.

Compilation procedure overview

1. 1Identify synthetic material production and imports — from industrial production statistics and trade data
2. 2Estimate synthetic material consumption — using supply-use balancing (domestic production + imports - exports)
3. 3Record waste generation by sector — from waste surveys and composition studies
4. 4Estimate waste collection and treatment — from municipal and industrial waste management records
5. 5Model mismanaged waste — as the difference between waste generated and waste formally collected
6. 6Estimate marine leakage — applying leakage factors to mismanaged waste based on proximity to marine environment

Step 1: Synthetic material production and imports

1From industrial production statistics (ISIC 20, 22) and customs trade data (HS chapters 39, 54, 55):

Flow	Quantity (tonnes)	Source
Domestic production of plastic resins	125,000	Industrial census
Imports of plastic products	68,000	Trade statistics
Exports of plastic products	42,000	Trade statistics
Net supply to domestic economy	151,000	Calculated

Step 2: Synthetic material consumption by sector

Consuming Sector	ISIC	Quantity (tonnes)	Share (%)
Food & beverage manufacturing	10-11	35,000	23.2
Retail trade (packaging)	47	28,000	18.5
Accommodation & food service	55-56	18,000	11.9
Fishing	0311	12,000	7.9
Construction	41-43	15,000	9.9
Households (direct consumption)	HH	38,000	25.2
Other industries	Various	5,000	3.3
Total consumption		151,000	100.0

Step 3: Waste generation

Waste Source	ISIC/Sector	Waste Generated (tonnes)	Plastic Content (%)	Plastic Waste (tonnes)
Food manufacturing	10-11	45,000	60	27,000
Retail & hospitality	47, 55-56	38,000	55	20,900
Fishing	0311	15,000	75	11,250
Construction	41-43	22,000	40	8,800
Households	HH	95,000	35	33,250
Other industries	Various	12,000	30	3,600
Total waste generated		227,000	—	104,800

1Material balance closure. The 46,200-tonne difference between consumption (151,000 tonnes) and waste generation (104,800 tonnes) represents the net addition to the stock of plastic products in use (durable goods with remaining service life), together with minor losses from degradation during the use phase. The SEEA CF material balance principle requires that all material inputs be accounted for in outputs, stock changes, or dissipative losses. This in-use stock change should be recorded in a separate physical balance sheet:

Opening stock of plastic products in use
  + Consumption
  - Waste generation
  - Use-phase dissipative losses
  = Closing stock of plastic products in use

2The recycling rate is calculated against waste generated, not total consumption: 18,500 / 104,800 = 17.7% (see Step 4). Compilers should clearly state the denominator when reporting recycling rates to ensure comparability with international reporting.

Step 4: Waste collection and treatment

Treatment Pathway	Quantity (tonnes)	Share (%)
Collected for recycling	18,500	17.7
Collected for incineration	12,300	11.7
Collected for controlled landfill	48,200	46.0
Total formally collected	79,000	75.4
Mismanaged waste	25,800	24.6
Total waste generated	104,800	100.0

Step 5: Mismanaged waste estimation

Geographic Zone	Mismanaged Waste (tonnes)	Share (%)
Coastal zone (<50km from coast)	14,800	57.4
Inland zone (>50km from coast)	11,000	42.6
Total mismanaged	25,800	100.0

Step 6: Marine leakage estimation

1Apply Jambeck et al. (2015) leakage factors as defined in Section 3.3. The values below are illustrative central estimates. Compilers should calibrate factors to national monitoring data or published country-level estimates where available.

Source Category	Mismanaged Waste (tonnes)	Leakage Factor (central)	Sensitivity Range (low—high)	Marine Leakage (tonnes)	Source basis
Coastal zone land-based	14,800	0.25	0.15 — 0.40	3,700	Jambeck et al. (2015), range from inadequately managed waste estimates17
Inland (via riverine transport)	11,000	0.08	0.02 — 0.15	880	Lebreton et al. (2017) riverine emission rates14; Lau et al. (2020) sensitivity18
Fishing gear losses (direct)	1,200	1.00	0.80 — 1.00	1,200	Richardson et al. (2019)21; gear losses assumed to enter marine environment directly
Maritime operational waste	450	0.60	0.10 — 0.60	270	Assumption pending peer review; see note below
Total marine litter input				6,050

2Note on the maritime operational waste factor. MARPOL Annex V requires all ships to deliver garbage to port reception facilities (PRFs) before discharge, with compliance monitored through Garbage Record Books and Port State Control (PSC) inspections. The 0.60 central value is an upper-bound assumption that does not reflect MARPOL Annex V compliance rates and should be replaced with a country-specific estimate based on PRF utilisation data (IMO GISIS database) and PSC inspection statistics. Where empirical national data are unavailable, compilers should report a sensitivity range rather than a single point estimate and flag the assumption as requiring expert peer review.

3Compilers should (1) cite the source for each leakage factor used, (2) report a low—high sensitivity range alongside the central estimate, (3) calibrate factors to national monitoring data where these exist, and (4) document any departures from published source-methodology values.

Interpretation

• 1Collection gap: 24.6% of plastic waste is mismanaged, representing the primary intervention target
• 2Coastal concentration: 57% of mismanaged waste is in coastal zones where leakage probability is highest (25% vs 8% for inland)
• 3Sector priorities: Fishing, retail/hospitality, and households together account for 62% of total plastic waste generation
• 4Marine leakage rate: 6,050 / 104,800 = 5.8% of plastic waste generated ultimately enters marine environment

5Policy implications:

• 6Expanding waste collection coverage in coastal zones from 75% to 85% would reduce coastal mismanaged waste and marine leakage from this source by an estimated 1,480 tonnes annually
• 7Extended producer responsibility for packaging (ISIC 10-11, 47) could address approximately 48,000 tonnes of plastic waste at source
• 8Fishing gear deposit-return schemes could recover a portion of the 1,200 tonnes of gear losses

9Quality assurance for this worked example is addressed in TG-0.7 Quality Assurance.

3.7 SDG 14.1 Alignment and Multi-Target Linkages

1SDG Target 14.1 states: “By 2025, prevent and significantly reduce marine pollution of all kinds, in particular from land-based activities, including marine debris and nutrient pollution”³³. SDG indicator 14.1.1 comprises an index of coastal eutrophication and floating plastic debris density³⁴.

Indicator components

1Floating plastic debris density is measured as items per square kilometre of sea surface or mass (grams or kilograms) per square kilometre, using beach litter surveys, visual surveys, net-based sampling (manta trawls, neuston nets), or remote sensing approaches.

2Index of coastal eutrophication (ICEP) addresses nutrient pollution separately and is not the focus of this Circular. See TG-3.4 Flows from Economy to Environment for nutrient accounting.

3Composite index construction. SDG 14.1.1 is currently reported as two parallel sub-indicators rather than a single numerical composite. Countries should report both sub-indicators with consistent temporal and spatial reference units, following the UNSD SDG 14.1.1 metadata document. Compilers should coordinate their marine litter and nutrient pollution accounting programmes to ensure temporal and spatial consistency between the two sub-indicator datasets. The UNSD SDG 14.1.1 metadata should be consulted directly before publication, as the composite methodology continues to be refined.

Multi-target linkages

• 1SDG 12.4 (Environmentally sound management of wastes) — Marine litter flow accounts quantify waste escaping management systems.
• 2SDG 12.5 (Reduce waste generation) — Time-series accounts track progress in material circularity as reflected in declining leakage rates.
• 3SDG 6.3 (Improve water quality) — Riverine litter transport estimates link land-based pollution to downstream marine impacts.

4The multi-indicator framework for deriving ocean policy indicators is addressed in TG-2.7 Pollution Flows.

Indicator derivation from accounts

Indicator	Calculation	Unit
Litter generation intensity	Litter generated / GDP	Tonnes per million USD
Per capita litter generation	Litter generated / Coastal population	kg per capita
Mismanaged waste rate	Mismanaged waste / Total waste generated	Percent
Marine leakage rate	Litter to ocean / Total waste generated	Percent
Fishing gear loss rate	ALDFG mass / Active gear mass	Percent
Beach litter accumulation	Beach stock change / Coastline length	Items per km
Clean-up effectiveness	Removed litter / Beach stock	Percent

1Guidance on indicator derivation and interpretation is in TG-2.7 Pollution Flows.

4. Data Sources and Compilation

1Compilation of marine litter and plastics accounts draws on multiple data sources. General guidance on data collection methods is in TG-4.1, TG-4.8, and TG-4.9. Administrative data sources are addressed in TG-4.3 Administrative Data.

2Key data sources include:

3Waste management statistics — National waste statistics and composition surveys, municipal solid waste data, recycling and recovery rates by material type, and industrial waste reporting.

4Environmental monitoring programmes — Beach litter surveys (national programmes, OSPAR, HELCOM, regional seas conventions); marine litter monitoring; microplastics monitoring; citizen science and clean-up organisation data.

5Maritime and fisheries data — Port reception facility records (MARPOL Annex V), fishing gear inventories and loss reporting, maritime incident databases, and vessel tracking data (AIS).

6Economic statistics — Industry production data for plastic-intensive sectors, trade data for plastic products, and tourism statistics.

7Modelling and estimation — Waste leakage models (Jambeck methodology and derivatives), river transport models, ocean circulation and debris transport models, and fragmentation and degradation models.

8International reporting — UNEP marine litter databases, regional seas convention assessments, and Global Partnership on Marine Litter data.

Compilation pathways and phased implementation

1Phase 1: Foundation — Beach litter survey data are the most widely available starting point. Countries with established beach monitoring programmes (OSPAR, HELCOM, or national programmes) can compile initial stock accounts for coastal compartments and use survey composition data to estimate source attribution.

2Phase 2: Flow estimation — Building on waste management statistics, compilers estimate land-based litter flows using the Jambeck methodology. Maritime source flows are estimated from fisheries and port data using the physical supply and use table framework (Section 3.3).

3Phase 3: Full accounts — Integration of floating and benthic stock data and refined geographic disaggregation produces complete stock-flow accounts. This phase requires investment in monitoring infrastructure and modelling capacity.

4Data gap assessment and prioritisation guidance is in TG-4.6 Data Harmonisation. Quality assurance considerations are addressed in TG-0.7 Quality Assurance.

5. Acknowledgements

1This Circular has been approved for public circulation and comment by the GOAP Technical Experts Group in accordance with the Circular Publication Procedure.

2Authors: [To be confirmed]

3Reviewers: [To be confirmed]

6. References and Further Reading

1This Circular should be read in conjunction with:

• 2SEEA Central Framework, Chapter III: Physical flow accounts, particularly section 3.6.5 on solid waste accounts³⁵
• 3GESAMP (2019). Guidelines for the monitoring and assessment of plastic litter in the ocean
• 4UNEP (2021). From Pollution to Solution: A Global Assessment of Marine Litter and Plastic Pollution
• 5SDG Framework, Target 14.1 and Indicator 14.1.1 methodology
• 6Regional seas convention marine litter monitoring protocols (OSPAR, HELCOM, Barcelona Convention, NOWPAP)
• 7TNFD disclosure recommendations for waste and pollution metrics³⁶
• 8Lau, W.W.Y. et al. (2020). Evaluating scenarios toward zero plastic pollution. Science
• 9Borrelle, S.B. et al. (2020). Predicted growth in plastic waste exceeds efforts to mitigate plastic pollution. Science
• 10SPREP (2018). Pacific Regional Action Plan: Marine Litter 2018-2025. Secretariat of the Pacific Regional Environment Programme.
• 11ISO 18830:2016 and ISO 19679:2016, Marine biodegradability test methods for plastic materials.

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Footnotes

1. 1

   UNEP (2021). From Pollution to Solution: A Global Assessment of Marine Litter and Plastic Pollution. Nairobi: UNEP, p. 10. ↩

2. 2

   GESAMP (2019). Guidelines for the Monitoring and Assessment of Plastic Litter in the Ocean, paragraph 2.1. ↩

3. 3

   United Nations (2015). Transforming our world: the 2030 Agenda for Sustainable Development. A/RES/70/1, Target 14.1. ↩

4. 4

   UN Statistics Division. SDG Indicator 14.1.1: Index of coastal eutrophication and floating plastic debris density. Metadata document. ↩

5. 5

   UNEP (2022). Resolution adopted by the United Nations Environment Assembly on 2 March 2022: End plastic pollution: towards an international legally binding instrument. UNEP/EA.5/Res.14. ↩

6. 6

   UNEP Intergovernmental Negotiating Committee on Plastic Pollution. Live status page: https://www.unep.org/inc-plastic-pollution. Compilers should consult this page for the current state of negotiations and any adopted reporting obligations. ↩

7. 7

   SEEA CF, paragraph 3.84. This aligns with the concept of waste in EU Directive 2008/98/EC Article 3(1). ↩

8. 8

   SEEA CF, paragraphs 3.268-3.278 and Table 3.18. ↩

9. 9

   SEEA CF, paragraphs 3.268-3.278. Paragraph 3.268 describes solid waste accounts as “useful in organizing information on the generation of solid waste and the management of flows of solid waste to recycling facilities, to controlled landfills or directly to the environment.” ↩

10. 10

    UN Statistics Division. SDG Indicator 14.1.1 Metadata. ↩

11. 11

    GESAMP (2019). Guidelines for the Monitoring and Assessment of Plastic Litter in the Ocean. IMO/FAO/UNESCO-IOC/UNIDO/WMO/IAEA/UN/UNEP/UNDP Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection. ↩

12. 12

    European Commission (2010). Guidance on the interpretation of the waste classification. Commission Notice 2010/C 252/03. ↩

13. 13

    SPREP (2018). Cleaner Pacific 2025: Pacific Regional Waste and Pollution Management Strategy 2016-2025. ↩

14. 14

    Lebreton, L.C.M. et al. (2017). River plastic emissions to the world’s oceans. Nature Communications, 8: 15611. ↩ ↩²

15. 15

    International Maritime Organization. London Convention (1972) and London Protocol (1996) on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter. ↩

16. 16

    SEEA CF, paragraphs 3.78-3.79. ↩

17. 17

    Jambeck, J.R. et al. (2015). Plastic waste inputs from land into the ocean. Science, 347(6223): 768-771. Inadequately managed waste leakage range 15-40%, central estimate 15%. ↩ ↩²

18. 18

    Lau, W.W.Y. et al. (2020). Evaluating scenarios toward zero plastic pollution. Science, 369(6510): 1455-1461. ↩ ↩²

19. 19

    Borrelle, S.B. et al. (2020). Predicted growth in plastic waste exceeds efforts to mitigate plastic pollution. Science, 369(6510): 1515-1518. ↩

20. 20

    SEEA CF, Table 3.18 and paragraphs 3.268-3.278. ↩

21. 21

    Richardson, K. et al. (2019). Estimates of fishing gear loss rates at a global scale. Fish and Fisheries, 20(6): 1218-1231. ↩ ↩²

22. 22

    Richardson et al. (2019) remains the primary source for global ALDFG loss-rate estimates. No comprehensive post-2019 update providing regional or gear-specific rates is yet available in the peer-reviewed literature. Compilers requiring country- or fishery-specific rates should consult national and regional fisheries management organisation (RFMO) data and outputs from the FAO/IMO GloLitter Partnerships programme (https://glolitter.imo.org/), which is developing improved gear-loss datasets by gear type and region. Hodgson (2022) is a legal analysis and does not contain gear-specific loss-rate data; Macfadyen et al. (2009) is a precursor study that informed Richardson et al. (2019) and should not be cited as an independent source of loss-rate values. ↩

23. 23

    International Maritime Organization. MARPOL Annex V: Regulations for the Prevention of Pollution by Garbage from Ships. ↩

24. 24

    Schmidt, C., Krauth, T., and Wagner, S. (2017). Export of plastic debris by rivers into the sea. Environmental Science and Technology, 51(21): 12246-12253. ↩

25. 25

    OSPAR Commission (2010). Guideline for Monitoring Marine Litter on the Beaches in the OSPAR Maritime Area. ↩

26. 26

    Classification of Environmental Protection Activities and Expenditure (CEPA), Class 3.2: Collection and transport. ↩

27. 27

    UN Statistics Division. SDG Indicator 14.1.1 Metadata. ↩

28. 28

    SEEA Ecosystem Accounting (2021), Chapter 5 on ecosystem condition; see Table 5.1 on condition variable classification and paragraphs 5.15-5.30 on ecosystem condition characteristics, including physical and chemical state (abiotic characteristics). ↩

29. 29

    SEEA CF, paragraphs 3.268-3.277 and Chapter VI on combined presentations. ↩

30. 30

    SEEA Ecosystem Accounting (2021), Chapter 3 on spatial units, particularly paragraphs 3.38-3.45 on marine areas. ↩

31. 31

    SPREP (2018). Pacific Regional Action Plan: Marine Litter 2018-2025. Secretariat of the Pacific Regional Environment Programme. https://pacific-data.sprep.org/system/files/Pacific%20Regional%20Action%20Plan%20-%20Marine%20Litter.pdf. UNEP (2021), From Pollution to Solution: A global assessment of marine litter and plastic pollution, Nairobi. ↩

32. 32

    SEEA CF, paragraphs 2.121-2.123 on geographical boundaries; see also paragraph 5.493 on spatial and temporal detail for water resources. ↩

33. 33

    United Nations (2015). Transforming our world: the 2030 Agenda for Sustainable Development. A/RES/70/1. ↩

34. 34

    UN Environment Programme (2021). SDG 14.1.1 Indicator Methodology: Index of Coastal Eutrophication and Floating Plastic Debris Density. ↩

35. 35

    United Nations et al. (2014). System of Environmental-Economic Accounting 2012 — Central Framework. New York: United Nations, paragraphs 3.268-3.278. ↩

36. 36

    TNFD (2023). Recommendations of the Taskforce on Nature-related Financial Disclosures, Metrics for nature-related risks and opportunities. ↩