Global Ocean Accounts Partnership Secretariat · GOAP Technical Guidance on Ocean Accounting · circular
This 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:
The 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.
This Circular owns the stock and flow accounts for marine litter and plastics: the material and source categories, the land-based and maritime input flows, the accumulation stocks by marine compartment, and the source attribution that connects them to economic units.
It specialises TG-3.4 Flows from Economy to Environment, which owns the residual-flow framework and the solid waste account this Circular’s flows enter, and cross-refers for survey and administrative data methods (TG-4.2, TG-4.3, TG-4.4) and readiness (TG-0.8).
Indicator derivation is not this Circular’s: SDG 14.1.1 and the circular-economy indicators are built in TG-2.7, TG-2.10 and TG-2.11; Section 3.7 states only what the accounts must carry for them. Nutrient pollution — the other half of SDG 14.1.1 — is TG-6.13 and TG-3.4.
This Circular requires familiarity with:
TG-0.1 General Introduction — foundational Ocean Accounts components and SIDS-specific considerations relevant to marine litter accounting in small island contexts.
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.
Marine 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 pollution. Plastics are the dominant material category, accounting for approximately 80 percent of all marine debris by count.
SDG Target 14.1 (preventing and reducing marine pollution) provides the primary policy anchor for this Circular. SDG indicator 14.1.1 specifically includes “floating plastic debris density” as a component of the index of coastal eutrophication and plastic debris density. 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 obligations, .
Scope — 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.
The 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 destinations, . 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.
Operational companion. This Circular specifies what a marine litter and plastics account contains and how its entries relate to one another. The GOAP Plastics Data Collection and Reporting Handbook specifies how a country finds, scores and generates the underlying data, and is the operational companion to this Circular. Where this Circular calls for a quantity, the Handbook names the instrument that produces it — the Plastics Data Checklist, the Global Plastics Data Tracker, the survey and sampling protocols, and the classification code sets. The two documents share a deliberate scope boundary: neither provides quantified guidance for microplastics or for certified biodegradable materials, and neither covers extraction and processing upstream of primary polymer manufacture.
The Handbook also establishes the maturity sequence inside which this Circular’s compilation phases sit. Improving individual data points yields a plastics data inventory — a coherent collection of data points measuring flows across the value chain. An inventory becomes a plastics account only when its data categories are reproduced periodically under a documented, standing methodology. The distinction has practical force: a single well-researched estimate of marine leakage is an inventory entry, not an account, and the accounting entries in Sections 3.3 to 3.6 assume the repeatability that Section 4 sets out to secure.
The starting point for most countries is sparse. A 2025 review of government-reported plastics data for every UN Member State found that 10 percent of countries report no plastics data at all and 60 percent report no data on waste generation. Compilers should expect the first cycle to be a data-development exercise as much as an accounting one, and should read Section 4 before attempting the flow and stock tables.
Marine 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.
Marine 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 framework. These indicators feed directly into TG-2.11 Resource Efficiency.
Where the case for cleanup rests on protecting tourism revenue, the revenue figure should be taken from the marine and coastal tourism segment compiled in TG-6.14, so that the benefit claimed and the sector account agree.
Stock 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.
The combined presentations approach in TG-3.8 Combined Presentations provides methods for integrating marine litter account data with economic and ecosystem condition accounts.
The terms on which marine litter accounts depend — mismanaged waste, leakage, litter, dumping — carry materially different definitions across the frameworks a compiler will draw on. UNEP’s 2024 assessment of plastics terminology records at least two competing definitions each for mismanaged waste, leakage and sanitary landfill, advocated respectively by the UNEP/IUCN Hotspotting methodology, the OECD, GIZ’s Waste Flow Diagram and UN-Habitat’s Waste Wise Cities Tool. The divergences are not cosmetic.
Accounts are not comparable across countries unless the definition applied to each entry is stated. Compilers should record, for every row of the flow and stock accounts, which definition has been applied and which source it comes from, and should not mix readings within a single time series. Where a country’s own legal definitions differ from all of the above, the national definition governs the account and the divergence is documented in the metadata.
The three waste measurement points must also be kept distinct, because they are measured at different places in the chain and are not interchangeable:
Collection and treatment figures should each be split between formal and informal management (Sections 3.3 and 3.5).
Plastics — the dominant component, requiring disaggregation by:
Bioplastics 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.
Other materials — including glass and ceramics, metal, rubber, textiles, paper and cardboard, processed wood, and other manufactured materials.
The GESAMP Guidelines for the monitoring and assessment of plastic litter in the ocean provide a harmonised categorisation framework. The European Waste Catalogue (EWC-Stat) offers additional detail for waste source identification.
Accounts assembled from production, trade and waste statistics inherit those statistics’ classifications. The code sets below are the ones a compiler will actually query, and using them consistently is what makes the material flow account in Section 3.6 reconcilable against official statistics.
The systems carrying a legal mandate — HS for trade, ISIC and NAICS for production, and the Basel Convention for waste — are the most consistently populated and should anchor the account; the others supply detail. One break in comparability is worth flagging: the Basel Convention’s plastic waste entries took effect on 1 January 2021, so transboundary plastic waste series do not run continuously across that date.
Where polymer disaggregation is attempted, the practical reporting set is PET, HDPE, PVC, LDPE and LLDPE, PP, and PS and EPS.
Land-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.
Sea-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.
Release routes within the waste system — uncollected, dumped and burned waste are distinct release routes rather than a single residual, and the distinction carries into the account:
Open burning matters to the account for a reason easily missed: it removes mass from the pool available for marine leakage while creating an emissions flow recorded elsewhere. Burned plastic should be recorded as an explicit outflow from the mismanaged waste pool rather than left implicitly available to leak, with the corresponding emissions cross-referenced to greenhouse gas inventory reporting (Section 3.3).
The 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 Introduction.
The SEEA CF notes that controlled landfills are within the economy, whilst uncontrolled disposal to the environment represents a residual flow. For marine litter accounting, waste reaching marine waters represents a flow to the environment recorded in residual flow accounts.
Figure 6.12.1 summarises marine litter stock-flow relationships (see also TG-3.4 Section 3.2).
· Figure 6.12.1
Source Scope: Escape residuals only; economy-side waste SUT out of scope -- TG-3.4.
Flow 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 litter flows require estimation of:
The 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 leakage:
Lau et al. (2020) extended this framework for scenario analysis of waste management interventions and material substitution. Borrelle et al. (2020) projected plastic waste growth trajectories.
For 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.
Default composition data where national studies are absent. Every term in a Jambeck-type estimator after coastal population depends on the plastic fraction of municipal solid waste, which many countries have never measured. Two fallbacks precede borrowing a neighbouring country’s figure. Countries reporting to the UNFCCC often already hold waste composition data compiled for national atmospheric emissions inventories, prepared in order to calculate landfill emissions; this is the preferred fallback because it is nationally specific and already quality-assured. Failing that, the IPCC’s regional default plastic shares of municipal solid waste provide a documented tier-1 assumption:
A regional default is an interim device, not a result. It should be tagged as such in the account’s metadata and replaced by a national waste composition study — systematic sampling and manual sorting of waste streams, typically 100-200 kg per sampling event, repeated to capture seasonal variation — as soon as one exists. Because composition studies are point-in-time and resource-intensive, they are usually run quarterly or annually rather than continuously, so the account should state which study year each composition assumption comes from.
Open burning. Where open burning is material, the IPCC provides a standardised estimator that can be adapted to yield the plastic mass burned rather than only the resulting emissions:
SW=P×Pfrac×SWc×Bfrac×365×10−6
Here SW is the total solid waste openly burned (Gg per year), P the population, Pfrac the fraction of the population burning waste, SWc per capita waste generation (kg per person per day), and Bfrac the fraction of waste burned relative to total waste treated. Multiplying through by the plastic fraction of the waste stream gives the plastic mass burned. Some of this waste originates from uncollected sources and some from collected sources, so compilers must take care not to deduct it twice.
Collection coverage and the informal sector. Mismanaged waste is normally derived as generation minus formal collection, which systematically overstates it wherever an informal collection sector operates. Three collection systems should be measured separately:
Informal recovery is not marginal. An estimated 15 million people work as informal waste collectors in developing countries, around one percent of the urban population. Omitting their recovery from the collected column transfers that mass to the mismanaged pool and then, through the leakage factor, into the marine leakage estimate. Collection coverage — the share of population or area with access to collection services — should be recorded alongside tonnages, because the two constrain one another.
The SEEA CF physical supply and use table for solid waste provides the structural framework:
For marine-specific accounting, “waste to environment” is disaggregated to distinguish:
Fishing 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 year. 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 organisations. Accounting requires data on fishing fleet composition, gear types, estimated loss rates, and conversion to mass units.
Vessel operational waste — MARPOL Annex V regulates discharge of garbage from ships. Accounting draws on port reception facility records, MARPOL incident reporting, and vessel surveys.
Offshore operations — Waste from offshore energy platforms, aquaculture installations, and maritime structures. Cross-reference to TG-6.9 Offshore Energy for offshore accounting context.
Cargo losses — Container losses and other cargo overboard incidents, reported under maritime incident databases.
Rivers 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 input. Accounting requires:
For 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.
Stock 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.
Table 3.4.1: Marine litter physical stock-flow account (tonnes)
The “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).
Note 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.
The accounting compartments correspond to distinct sampling problems, and the appropriate protocol differs for each. The mapping below follows the IUCN Global Ecosystem Typology so that litter monitoring aligns with the spatial units used for ecosystem accounting.
Sampling in pelagic waters requires specialist and costly platforms. The recommended practice is to acquire these observations opportunistically — during biodiversity surveys, oceanographic research cruises, fisheries assessments, or offshore engineering and exploration missions — rather than commissioning dedicated survey effort that a national programme is unlikely to sustain. Compilers should record the survey platform alongside each estimate, because opportunistic sampling carries spatial biases that a dedicated design would avoid.
Remote sensing. Satellite imagery, drone survey, thermal imaging, multispectral analysis, LiDAR volume estimation and fixed monitoring cameras each address a different part of the detection problem, and openly available imagery libraries make several of them inexpensive. Two constraints govern their use in accounts. Detection must be converted to quantity through a validated model, and results must be ground-truthed at selected locations before they enter the account; without that step remote sensing yields extent, not mass. Resolution, cloud cover and seasonality all interrupt time series, so acquisition conditions should be documented for each period. Thermal imagery additionally detects the heat signatures of active open burning, linking this method to the burning estimator in Section 3.3.
Beach litter is the most accessible stock for monitoring, with established survey methodologies. Stock accounts record mass or item counts per unit area (beach length, surface area), aggregated to total coastal stock and disaggregated by material category.
Beach stock accounts recognise that beaches are dynamic interfaces:
Clean-up activities should be recorded as economic flows (environmental protection expenditure under CEPA 3) and their effect on beach stocks quantified. This links to environmental expenditure accounts in TG-3.7 Governance Accounts.
Surface 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 parameter. Stock accounts for floating litter face specific challenges:
Global 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.
Litter 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.
Benthic 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 variable.
Effective 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 applies.
Industry sources of marine litter, classified by ISIC:
Where 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.
Households 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.
The informal collection and recovery sector is a recovery pathway rather than a source, and misplacing it distorts both the collected column and the mismanaged residual. It is also the hardest segment to enumerate: operations are irregular, records are rarely kept, and engagement depends on trust that a statistical exercise cannot assume. The practical attribution routes are cooperative-level reporting of recovered volumes by material type, market price data from itinerant buyers and aggregators, and recycler input records traced back to supply channel. Where the sector is enumerated, the corresponding employment and livelihood data should be captured in the same exercise (Section 3.7).
Coastal zone delineation — Coastal zone definitions should align with administrative boundaries whilst recognising functional connectivity to marine waters. See TG-1.2 Marine Spatial Planning.
Catchment-based accounting — River catchments as accounting units enable tracking of riverine litter pathways.
Maritime zone accounting — Recording of sea-based source litter by location (territorial sea, EEZ, high seas) supports jurisdictional analysis.
Transboundary 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). For SDG 14.1.1 reporting, domestic source attribution takes precedence, and transboundary flows should be reported as supplementary information.
The SEEA CF supports sub-national disaggregation where data permit. Priority geographic units include coastal municipalities, river catchments with marine outlets, port areas and shipping lanes, and marine protected areas.
This section presents a worked example tracking plastics from production through consumption, waste generation, collection and treatment, to marine leakage.
The procedure is a material flow analysis: a systematic quantification of the flows and stocks of a material within a defined system boundary over a defined period, closed by mass balance. Stated formally it has five stages — system definition (geographical and temporal boundaries, processes and actors), data collection, flow quantification, balance calculation, and visualisation and interpretation. The balance stage is what converts a collection of unrelated statistics into an account: an unexplained residual is either a real stock change or a data error, and the analysis must say which.
National precedents exist and are worth consulting before designing a first compilation. Sri Lanka’s national plastic waste inventory (2024) and Statistics Norway’s plastic account are the closest analogues to the procedure below, both built as national-scale material flow analyses; the Netherlands, Germany (healthcare sector), Australia, New Zealand, and a four-country South-East Asian study through the ERIA Regional Knowledge Centre on Marine Plastic Debris provide further worked national and sectoral examples.
From industrial production statistics (ISIC 20.16 and 22.20) and customs trade data (HS 3901-3914 for primary forms, 3916-3926 for products, and 3915 for waste and scrap; HS chapters 54 and 55 additionally cover the man-made filaments and staple fibres relevant to synthetic textiles):
Material 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:
The collected-for-recycling rate is calculated against waste generated, not total consumption: 18,500 / 104,800 = 17.7%. It is a collection rate, not a recycling rate (see the measurement-point note in Step 4). Compilers should clearly state the denominator when reporting recycling rates to ensure comparability with international reporting.
Measurement point of the treatment figures. The rows above are collection figures, measured at the point of collection and before sorting, and they therefore include contamination and material that will be rejected downstream. The 18,500 tonnes collected for recycling is not the tonnage recycled. The recycling rate international reporting expects is built on recovered tonnes: material that completes the recycling process and leaves the facility as saleable recyclate. Compilers holding both figures should report the recovered-tonnes rate as the headline and the collected-for-recycling rate as a supplementary measure of collection performance, stating the measurement point for each; the gap between them is itself a useful indicator of sorting loss. Where only collection data exist, the rate must be labelled a collection rate and not a recycling rate. Facility-level reject and residual waste tonnages, where reported, close the difference.
Apply 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.
Note 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.
Compilers 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.
Policy implications:
Quality assurance for this worked example is addressed in TG-0.7 Quality Assurance.
SDG 14.1.1 is derived in TG-2.7 Pollution and Other Flows to Environment Section 3.5, and its MEA reporting route in TG-2.10, . Neither the indicator definition, the sub-indicator structure nor the composite construction is restated here. This Section states only what the litter accounts must supply so that the indicator can be built from them without a parallel data collection.
Floating plastic debris density — the sub-indicator this Circular feeds — is reported as items or mass per square kilometre of sea surface. The stock accounts at Section 3.4 must therefore carry the surveyed area alongside the count or mass, in the compartment the indicator expects (sea surface, not beach or seafloor), and at a temporal reference matching the reporting year. An account that records national totals without the denominator cannot supply the indicator.
Index of coastal eutrophication (ICEP) is the other sub-indicator and is outside this Circular; nutrient accounting is at TG-3.4 Flows from Economy to Environment and TG-6.13 Section 3.2. The two sub-indicators are reported in parallel rather than combined, so the practical requirement on a compiler running both is that the spatial and temporal reference units match; where a country’s litter surveys and nutrient monitoring use different coastal segmentations, reconciling them is the work that has to be scheduled.
Marine litter accounts describe a workforce as well as a material, and the plastics data system that produces them can carry social indicators at marginal additional cost. Employment across the value chain (production, collection, sorting, recycling, administration) with demographic breakdown; formal against informal participation rates; income levels compared with regional living wage standards; working hours and occupational injury and illness rates; and community awareness and participation in collection are all collectable through the same household and workforce surveys that generate waste composition and disposal-behaviour data. These indicators support SDG 1, 3, 5, 8, 10, 11 and 12, and they are the evidence base for a just transition in waste management — a question that arises directly whenever an account identifies informal recovery as a material part of the collection system (Section 3.5).
The multi-indicator framework for deriving ocean policy indicators is addressed in TG-2.7 Pollution Flows.
Guidance on indicator derivation and interpretation is in TG-2.7 Pollution Flows.
Compilation of marine litter and plastics accounts draws on multiple data sources. General guidance on data collection methods is in TG-4.1 Remote Sensing and Geospatial Data, TG-4.2 Survey Methods for Ocean Economic Activity, and TG-4.4 Citizen Science and Community-Based Monitoring. Administrative data sources are addressed in TG-4.3 Administrative Data.
Key data sources include:
Waste management statistics — National waste statistics and composition surveys, municipal solid waste data, recycling and recovery rates by material type, and industrial waste reporting.
Environmental monitoring programmes — Beach litter surveys (national programmes, OSPAR, HELCOM, regional seas conventions); marine litter monitoring; microplastics monitoring; citizen science and clean-up organisation data.
Maritime and fisheries data — Port reception facility records (MARPOL Annex V), fishing gear inventories and loss reporting, maritime incident databases, and vessel tracking data (AIS).
Economic statistics — Industry production data for plastic-intensive sectors, trade data for plastic products, and tourism statistics.
Modelling and estimation — Waste leakage models (Jambeck methodology and derivatives), river transport models, ocean circulation and debris transport models, and fragmentation and degradation models.
International reporting — UNEP marine litter databases, regional seas convention assessments, and Global Partnership on Marine Litter data.
The repositories below should be checked before any new collection is commissioned. Several hold country-level data that a national programme has itself reported and may not know is retrievable.
Methodological guidance to pair with these sources: GESAMP (2019) for ocean plastic litter monitoring; UNEP (2021) Understanding the State of the Ocean for SDG 14.1.1, 14.2.1 and 14.5.1 measurement; UNEP/IOC (2009) for beach, benthic and floating litter surveys; UNEP (2020) for rivers and lakes; UNEP/IUCN national guidance on plastic pollution hotspotting; the IUCN marine plastic footprint methodology for leakage at the waste stage; and the European Commission’s 2023 guidance on monitoring marine litter in European seas. The GPML Community of Practice on Harmonisation of Monitoring and Assessment of Plastic Pollution is the forum in which the interoperability of these methods is being worked out, and compilers with unresolved comparability problems should raise them there rather than resolving them privately.
Score what exists before generating anything new. Two independent scales apply to every data point, and the pairing matters: data can be available but unreliable, and a reliable one-off study is not a usable account input.
Availability:
Reliability:
Applying these scales to the entries this Circular requires yields the honest statement of account quality on which the sensitivity ranges in Section 3.6 depend. A marine leakage estimate built on medium-reliability composition data and default leakage factors should be published with that provenance visible rather than as a point estimate.
Not every gap is worth closing, and the cheapest are rarely the most useful. Score each data category on four dimensions and prioritise the lowest total, so that low availability, low reliability, easy remedy and high impact all pull in the same direction:
Ease and impact are judgements rather than measurements and should be drawn from the stakeholders identified below, not assigned by the compiling agency alone. The same technique settles which plastics to cover first: wholly plastic products are easier to measure than composites, and high-volume or policy-salient streams repay measurement sooner. A completed prioritisation should be validated through expert review, stakeholder consultation, cross-reference to national policy objectives and international commitments, and a final check of available resources against ambition.
Each category fails in characteristic ways, and the countermeasures are known:
Verification of any individual figure follows four steps: check the definition in use; cross-validate against an independent source; account for double-counting wherever the method sums across sources; and confirm that assumptions and conversion factors are listed, evidence-based and referenced.
Divergent figures for the same quantity are the normal condition rather than an exception, and the account must resolve them visibly. Establish a hierarchy of data reliability with a designated primary source for each category and a protocol governing when a secondary source may override it. Triangulate across independent sources, and document rather than suppress the discrepancies. Where a figure is missing, bound it: establish upper and lower values, run a sensitivity analysis, and state the confidence level. Proxy measurement (economic indicators, plastic-to-product weight ratios, data from comparable economies), statistical modelling and step-down scaling from national to sub-national estimates are all legitimate provided the derivation is recorded. Standardised templates, conversion tools between classification systems, automated validation at the point of data entry, and expert review panels for persistently problematic figures are the institutional means of holding this together. Every reconciliation decision belongs in the metadata with its rationale.
Units follow a single convention: tonnes or kilotonnes for absolute quantities, and kilograms per capita for cross-country comparison. Each data point carries at minimum its weight, reference year and source, and wherever possible its polymer type, the industry of consumption or disposal, and the assumptions and conversion factors used to derive it.
The generic institutional readiness framework — the mandate questions, the lead-agency choice, the coordination architecture and the readiness self-assessment — is set out in TG-0.8 Implementation Readiness Assessment Sections 3.1 and 3.5, and in TG-4.7 National Data Coordination Architectures. It is not restated here. What follows is what is specific to a plastics account.
None of the above survives a change of government or a staff departure unless it is somebody’s job. Securing the institutional foundation precedes stakeholder engagement, because an agency without a mandate cannot compel data provision, and coordination without a designated lead fragments. Four questions settle the arrangement: which agencies already hold legal authority to collect plastics-related data; which is best placed to lead, typically the environment ministry, the national statistical office or the waste management authority; what each agency already collects that could be reused rather than duplicated (customs for trade, industry ministries for production, municipalities for waste); and what inter-agency data-sharing protocols exist, with what formats, timelines, quality assurance procedures and named contact points.
Stakeholder mapping proceeds in three phases: desktop research across agencies, trade databases, business registries, waste service providers, NGOs and research institutions; initial consultations to validate the list and begin building relationships; and snowball identification in which each stakeholder names others, the stage that surfaces the informal sector and other actors absent from registries. The resulting arrangement is best expressed as an action matrix stating, for each stakeholder, the lifecycle stage covered, the data to be provided, the reporting frequency, the path the data travels, and the support required. Indicative frequencies run monthly for customs and municipal collection records, quarterly for producers, recyclers and the coordinating agencies, and annually for survey-based consumption and research inputs.
The obstacles are predictable and should be planned for rather than discovered: institutional and sectoral data silos; overlapping or conflicting mandates; commercial confidentiality; political sensitivity around waste generation rates and illegal dumping; limited technical capacity; interoperability between systems; and the difficulty of sustaining engagement and funding beyond a pilot phase.
An account is repeatable when the obligation to produce it is written down. Legislative frameworks should establish which agency is responsible for what; set reporting thresholds, frequencies and deadlines; specify verification procedures and consequences for non-compliance; protect commercial sensitivity while allowing publication of aggregates; and align with international commitments, including the instrument under negotiation on plastic pollution. Precedents include the EU Packaging and Packaging Waste Directive (94/62/EC, as amended) together with the 2019 Single-Use Plastics Directive, which mandate material-specific packaging waste reporting; South Korea’s 2003 Act on the Promotion of Saving and Recycling of Resources, whose extended producer responsibility system produces one of the most detailed national plastics datasets; and the 2022 amendments to the Canadian Environmental Protection Act, which created a national plastics registry with threshold-based reporting by manufacturers, importers and users.
Three supporting practices keep a standing account functioning. Continuing engagement, through multi-stakeholder advisory committees, industry working groups on sector-specific measurement problems, and user forums that keep the statistics useful — the Australian Packaging Covenant Organisation and the UK Plastics Pact are working models. Continuing capacity development, through training in collection and validation methods, documented standard operating procedures, knowledge transfer between senior and incoming staff, and research partnerships; Eurostat’s European Statistical Training Programme offers modules on plastic waste characterisation and material flow accounting. And digitalisation: secure online reporting in place of paper submission, automated validation at the point of entry, application programming interfaces transferring data directly from company systems, integration with customs data and business registries to reduce reporting burden, and mobile tools for field waste characterisation. Germany’s LUCID packaging register is an operating example of the reporting-platform pattern. Dedicated funding can be sought through environmental fees on plastic products, earmarked allocations from waste management budgets, or international financing for plastic pollution and circular economy work.
Phase 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.
Phase 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).
Phase 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.
These three phases describe the widening coverage of the litter account specifically, and sit inside the general phased implementation pathway at TG-0.8 Section 3.2 rather than replacing it. They are also orthogonal to the maturity ladder set out at the start of Section 3: a Phase 1 compilation repeated annually under a documented methodology is already an account, whereas a Phase 3 compilation produced once is an inventory entry. Countries should secure repeatability at whatever coverage they can sustain before extending coverage, because a broken time series cannot be repaired retrospectively.
Data gap assessment and prioritisation guidance is in TG-4.6 Data Harmonisation. Quality assurance considerations are addressed in TG-0.7 Quality Assurance.
Authors: [To be confirmed]
Reviewers: [To be confirmed]
This Circular should be read in conjunction with:
Plastics Data Collection and Reporting Handbook — the operational companion to this Circular.
Cite this report
Marine Litter and Plastics Accounting (2026) (GOAP Technical Guidance on Ocean Accounting, TG-6.12, v0.8.1). GOAP Secretariat. https://guidance.oceanaccounts.org/circulars/section-6/6-12-marine-litter/
guidance.oceanaccounts.org/circulars/section-6/6-12-marine-litter
© 2026 Global Ocean Accounts Partnership Secretariat · CC BY-NC 4.0 · The report, its PDF and this deck are built from the same source.
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