When governments approve a new wastewater plant, landfill, incinerator or power station, they rely on environmental impact assessments to judge whether the project is safe. These reports often contain complex computer models that show how pollution spreads in the air and water.
But a new February 2026 report from the Asian Development Bank argues that many assessments may be missing a crucial first step. Before modeling how pollution spreads, officials must first accurately determine how much pollution is produced at the source. If the starting numbers are wrong, even the best computer model will give misleading results.
Authored by senior environmental specialist Xin Ren, the study draws on methods used by global institutions such as the Intergovernmental Panel on Climate Change, the European Environment Agency, the United States Environmental Protection Agency and the World Health Organization. Its core message is simple: environmental protection begins with solid, realistic numbers at the smokestack, wastewater pipe or landfill cell.
Four Practical Ways to Measure Pollution
The report explains four main ways pollution can be estimated. The first is analogy, using data from similar facilities that already exist. If a new plant uses the same technology as an existing one, its emissions are likely to be similar.
The second method uses emission factors. These are average values developed over many years that link a specific activity, such as burning one ton of waste, to a typical amount of pollution.
The third approach uses mass balance formulas based on a basic scientific rule: what goes into a system must come out in some form. For example, if fuel contains sulfur, that sulfur must appear in emissions or waste.
The fourth method is direct measurement, which is the most reliable but not always practical because it requires time, equipment and laboratory capacity.
The report emphasizes that simple, well-tested methods often work better than complicated modeling, especially in developing countries with limited resources.
What Happens in Sanitation and Waste
In urban sanitation, wastewater volume is often estimated as 80 to 90 percent of water used by households, since some water is lost through leakage or evaporation. Domestic wastewater tends to have similar characteristics worldwide, making estimation more reliable.
Treatment plants also generate sludge. On average, about 6 to 9 tons of sludge are produced for every 10,000 cubic meters of wastewater treated. Managing this sludge safely is a major challenge. Odor from sludge handling is another common concern in growing cities.
Landfills present different risks. Rainwater mixing with waste creates leachate, a highly polluted liquid that must be treated. Landfills also produce methane, a powerful greenhouse gas. Estimating methane emissions accurately is essential for climate reporting and safety planning.
Waste treatment through anaerobic digestion and composting can reduce landfill use, but these systems also produce wastewater and air emissions. Without proper control, they can cause odor and water pollution.
Incineration, often promoted as waste-to-energy, reduces waste volume but creates its own pollution. High moisture content in waste can produce leachate before burning. Incinerators also emit gases such as nitrogen oxides, sulfur dioxide and fine particles. Even after burning, about one quarter of the original waste may remain as ash that must be disposed of safely.
The Energy Sector Challenge
Thermal power plants, especially those using coal, oil or gas, are major pollution sources. Sulfur dioxide emissions are linked directly to sulfur content in fuel. Particulate matter depends on ash content and the effectiveness of dust filters. Heavy metals reflect their presence in fuel and the performance of pollution control systems.
Nitrogen oxides are harder to estimate because they form both from fuel and from high-temperature reactions during combustion. Cooling systems in power plants also consume large amounts of water and can cause thermal pollution if discharged back into rivers without proper control.
The report shows that many of these emissions can be estimated with straightforward formulas and emission factors, provided the underlying data are reliable.
A Warning About “Modeling the Limit”
One of the report’s strongest criticisms concerns a practice in some environmental assessments: using the legal emission limit as the input for pollution models instead of predicting actual emissions.
In simple terms, some projects assume they will emit exactly the maximum amount allowed by law and then model how that amount spreads in the environment. This approach can either exaggerate impacts or hide real problems. It may also lead to unnecessary design costs or weaken regulatory standards.
The Asian Development Bank’s message is clear. Environmental impact assessments should guide project design early, helping avoid or minimize pollution before construction begins. That requires honest, transparent and realistic estimates of emissions at the source.
In a world increasingly dependent on sophisticated models and climate accounting, the report offers a practical reminder: environmental protection starts with knowing what is really coming out of the pipe or the stack. Without that foundation, everything built on top of it becomes uncertain.