Methodological Approaches to Green Accounting: Expenditure, Physical, and SNA Extension Systems

Traditional GDP tells us how much a country produces, but it says nothing about the environmental costs of that production. Green accounting tries to fix this gap by adjusting national income figures to reflect pollution, resource depletion, and ecological degradation. But how exactly do economists and statisticians go about it? There are three major methodological approaches – pollution expenditure accounting, physical accounting, and extensions of the System of National Accounts (SNA). Each tackles the environment-economy relationship from a different angle, with its own strengths and trade-offs.

Pollution expenditure accounting 🔗

Pollution expenditure accounting is one of the earliest and most straightforward methods. It tracks how much money governments, businesses, and households spend on reducing or eliminating environmental damage – think wastewater treatment, air filtration systems, or hazardous waste management.

The United States began maintaining data series on pollution abatement and control expenditure as early as 1972. The OECD developed a methodology for Pollution Abatement and Control (PAC) Expenditure that became a widely adopted framework , and many other industrialised nations followed suit. Environmental protection expenditure (EPE) statistics show how much different sectors spend on reducing or eliminating pressures on the environment, such as air or water pollution . These figures are typically broken down by sector – industry, government, and households – and classified using standardised categories like the Classification of Environmental Protection Activities (CEPA).

How pollution expenditure data is used 🔗

Environmental expenditure data provide an important basis for developing effective and efficient environmental policies . Policymakers use them to assess whether sufficient resources are being directed toward environmental priorities, identify financing gaps, and evaluate trade-offs between new investments and maintenance of existing infrastructure. For instance, if a country’s spending on air quality control is stagnant while air pollution levels are rising, that discrepancy signals a problem.

Limitations of the expenditure approach 🔗

Despite its practicality, pollution expenditure accounting has notable shortcomings. First, the data only capture expenses that have already been incurred. They do not reflect environmental damage that goes unaddressed or future liabilities. Second, there is a risk of double-counting. Materials and resources used in pollution abatement may already be included in value-added calculations within the national accounts. Counting them again as environmental expenditures inflates the figures.

Third – and perhaps most misleadingly – comparing total pollution abatement spending with GDP can paint a distorted picture. GDP measures primary economic output without double-counting intermediate inputs. Pollution expenditure, on the other hand, is a mix of intermediate and final costs. Stacking these two numbers side-by-side can suggest that environmental spending is a larger (or smaller) share of the economy than it actually is.

Physical accounting 🔗

Physical accounting takes a completely different route. Instead of measuring the environment in monetary terms, it tracks changes in environmental assets using physical units – tonnes of carbon emitted, hectares of forest lost, cubic metres of water consumed, or indices of biodiversity. The idea is to supplement conventional economic accounts with non-monetary data about the state of natural resources.

Countries like France, Germany, Norway, and Sweden have been pioneers in this area. France, for instance, developed its Patrimoine Naturel accounts as early as the 1980s to monitor changes in natural heritage. Germany built extensive material and energy flow accounts that track the physical throughput of its economy. Norway developed resource accounts for oil, gas, forests, and fish stocks.

The Netherlands’ NAMEA system 🔗

The most well-known example of physical accounting is the Netherlands’ National Accounting Matrix including Environmental Accounts (NAMEA). NAMEA shows environmental pressures in physical units that are consistent with the monetary figures in the national accounts . It converts emissions from various pollutants into “theme equivalents” – grouping them under categories like the greenhouse effect, ozone depletion, and acidification.

Since 1994, the standard national accounts publication in the Netherlands has contained not only the conventional economic accounts, but also an integrated system of environmental and economic accounts . This setup allows analysts to compare each industry’s contribution to GDP and employment against its contribution to environmental problems. For example, a sector might represent 5% of GDP but be responsible for 20% of the country’s greenhouse gas emissions – a comparison that becomes immediately visible in NAMEA.

NAMEAs now exist in several European countries including Denmark, Germany, the UK, Sweden, and Japan , making it one of the more widely adopted physical accounting frameworks.

Limitations of physical accounting 🔗

Physical accounting is valuable because it avoids the controversial task of putting a monetary price tag on nature. But it has its own set of challenges.

Unit incomparability: Tonnes of CO₂ cannot be directly compared with hectares of deforested land or cubic metres of polluted water. Each environmental asset uses a different unit of measurement, making it difficult to aggregate impacts into a single summary figure.

Difficulty in condensing information: Because there is no common currency (like money), it is hard to create compact descriptions of overall environmental status. Policymakers who need to set priorities across different environmental problems – say, air pollution versus water scarcity – find it difficult to weigh incommensurable physical data against each other.

Data demands: Physical accounting requires extensive and continuous data collection across many resource categories. Not all countries have the statistical infrastructure for this, particularly developing nations.

Severity blindness: A tonne of a mildly harmful pollutant and a tonne of a highly toxic one look the same in raw physical terms. Without some form of weighting or valuation, physical accounts may not adequately communicate which environmental problems are most urgent.

Extension of SNA-type systems 🔗

The most ambitious approach to green accounting involves modifying the existing System of National Accounts itself to incorporate environment-economy interactions across all accounts. Rather than running a parallel data system (as physical accounting does) or tracking a narrow set of expenditures, this method restructures national accounting from the inside out.

Two major frameworks represent this approach: the UN System of Environmental-Economic Accounting (SEEA) and the Environmental and Natural Resource Accounting Project (ENRAP) developed in the Philippines. While both aim to expand conventional accounts to reflect the environment, they differ in important ways.

The SEEA framework 🔗

The SEEA organizes and presents statistics on the environment and its relationship with the economy, bringing together economic and environmental information into a common framework . It follows a similar structure to the SNA and uses compatible concepts, definitions, and classifications. The SEEA Central Framework was adopted by the United Nations Statistical Commission as the first international statistical standard for environmental-economic accounting in 2012 .

The SEEA has several core objectives. It aims to separate environment-related flows and stocks from conventional economic data, link physical resource accounts with their monetary counterparts, assign economic values to environmental goods and services, measure natural capital as an asset class, and generate environmentally adjusted economic indicators such as “green GDP.”

The system monitors pressures exerted by the economy on the environment (in terms of resource extraction and emissions), impacts in terms of changes in environmental condition, and how the economy responds through spending on environmental protection and resource management .

Key components of SEEA 🔗

The SEEA is organized into four broad categories of accounts:

Physical flow accounts: These cover environmental flows – the movement of natural inputs, products, and residuals between the environment and the economy, and within the economy, in both physical and monetary terms . This includes tracking energy, water, materials, emissions to air, and waste generation.

Environmental asset accounts: These record the stocks of individual natural assets – minerals, timber, water, fish, land – and how they change over time due to economic activity and natural processes. The SEEA follows an accounting structure similar to the SNA and uses consistent concepts to facilitate the integration of environmental and economic statistics .

Environmental protection expenditure accounts: These track monetary flows associated with environmental activities – how much governments and businesses spend on pollution control, waste management, and ecosystem restoration.

Environmentally adjusted aggregates: Using data from the other three account types, SEEA enables the calculation of adjusted macroeconomic indicators. These include environmentally adjusted net domestic product (EDP), which accounts for the depletion of natural resources and the costs of environmental degradation.

The ENRAP approach 🔗

Environmental accounting in the Philippines started in 1990 under the Environmental and Natural Resources Accounting Project (ENRAP) . Funded by USAID, ENRAP was designed to modify the Philippines’ national economic accounts so they could better reflect interactions between the economy and the natural environment.

ENRAP addresses deficiencies in the SEEA approach by explicitly recognizing that the natural environment is a productive economic sector . While SEEA adheres closely to SNA conventions and minimises the use of estimated (imputed) values, ENRAP encourages the use of imputation approaches that draw on techniques common in the environmental economics literature . In practical terms, this means ENRAP assigns economic values to services that nature provides for free – such as the waste absorption capacity of rivers or the air filtration role of forests – even when no market transaction exists for these services.

Multiple phases of ENRAP have been implemented in the Philippines, covering areas like waste disposal services, pollution loads and control costs, pollution damage, natural resource depreciation, and non-market household production . The data generated from ENRAP have been applied to national policy decisions, particularly around pollution management and production technology improvements.

SEEA vs. ENRAP: key differences 🔗

The fundamental distinction is philosophical. SEEA adopts conventional SNA definitions of productive sectors and attempts to minimize the use of imputations to maintain a close relationship with the existing national accounts . ENRAP, on the other hand, emphasizes consistency with economic theory, even if that means departing from SNA conventions.

For example, SEEA does not account for many non-marketed environmental services (like clean air or water purification by wetlands) in its formal accounting structure. ENRAP does, by treating the environment as a sector of the economy that provides valuable outputs. This makes ENRAP theoretically richer, but also more reliant on estimated values that can be debated.

The goals of ENRAP are to build data useful for analysis of public policy and to encourage policy-makers to use that data . SEEA, by contrast, focuses more on generating a standardised, internationally comparable statistical framework. Both approaches have their merits, and many experts argue they are complementary rather than competing.

Why these approaches matter together 🔗

No single methodology captures the full picture of how economies interact with the environment. Pollution expenditure accounting gives us a measure of economic effort. Physical accounting provides concrete, measurable data on resource stocks and environmental pressures. SNA extensions like SEEA and ENRAP attempt to integrate both monetary and physical information into a unified framework.

Environmental accounts provide an integrated framework for data, indicators, and analysis, and integrating environment-related data with the national accounts framework makes the resulting indicators more consistent and permits alignment with the social aspects of sustainable development . In practice, countries often use a combination of these approaches. The Netherlands, for example, uses physical accounts (NAMEA) alongside its participation in the SEEA framework. The Philippines has run ENRAP concurrently with a SEEA pilot project.

The broader trend is toward convergence. Since its adoption in 2012, the SEEA Central Framework has evolved in response to new demands for integrated environmental and economic data in support of climate change, circular economy, biodiversity, and other policies . The SEEA Ecosystem Accounting standard, adopted in 2021, extends the framework further by incorporating spatially explicit data on ecosystem extent, condition, and services.

As environmental crises intensify, the ability to measure what is happening to natural capital – and to integrate those measurements into the same accounts that guide economic policy – becomes essential, not optional.

What do you think? Should countries prioritise one green accounting method over others, or is a hybrid approach that combines expenditure, physical, and SNA-based accounting the most realistic path forward? And how much weight should imputed values for non-market environmental services carry in official national accounts?

References

1. https://www.sciencedirect.com/science/article/abs/pii/S0954349X98000587
2. https://seea.un.org/content/about-seea
3. https://link.springer.com/chapter/10.1007/978-94-017-1433-4_6
4. https://seea.un.org/ecosystem-accounting