The Bureau of Indian Standards (BIS), through its Environment and Ecology Department (EED) and the Air, Soil and Noise Pollution Control Sectional Committee, EED 02, has taken up an important new draft Indian Standard titled “Methodology for Preparation of Industrial Emission Inventory – Code of Practice.”
The document, identified as EED 2 (34315) WC, has been issued as a Wide Circulation Draft for Indian Standard for review and comments. The draft was circulated on 31 August 2026, with the last date for submitting comments specified as 30 October 2026.
What is the Proposed Standard About?
Industrial activities are significant sources of air pollutant emissions. Preparing a reliable industrial emission inventory is therefore important for understanding emission sources, estimating pollution loads, planning environmental management measures and evaluating emission trends.
The proposed BIS methodology aims to establish a systematic and transparent framework for preparing industrial emission inventories. According to the draft, it covers:
- Identification and classification of emission sources
- Collection of activity data
- Selection of appropriate emission estimation methods
- Calculation of emissions
- Quality Assurance and Quality Control (QA/QC)
- Documentation and reporting
- Periodic updating of emission inventories
The proposed methodology may be used for existing and new industrial units, industrial clusters and sectors.
Why is an Industrial Emission Inventory Important?
An emission inventory provides a structured picture of where emissions are generated and how much is being released.
The draft highlights that reliable emission inventories can support:
- Air quality management
- Environmental planning
- Pollution control strategies
- Assessment of mitigation measures
- Environmental Impact Assessment
- Air quality modelling
- Industrial cluster assessments
- Environmental management planning
- Regulatory reporting
- Tracking emission trends over time
A consistent methodology can also improve the comparability and reliability of emission inventory data across different industries and locations.
Key Principles Proposed by BIS
The draft states that an industrial emission inventory should be:
Transparent, Consistent, Comparable, Complete and Accurate.
The methodology selected should be appropriate to the purpose of the inventory, the availability of data and the required level of accuracy.
It also proposes that assumptions, data sources, calculation methodology, uncertainty and limitations should be properly documented.
Identification of Emission Sources
One of the important aspects of the proposed methodology is the identification and classification of emission sources within a defined inventory boundary.
Sources may include:
- Point sources
- Area sources
- Line sources
- Fugitive emission sources
- Process releases
- Combustion sources
- Solvent, chemical and material handling
- Transportation and internal combustion sources
- Stationary DG sets and off-road engines
The draft also recommends preparing a source map or flow diagram to illustrate the location and nature of emission sources.
Pollutants Covered
The inventory may include pollutants based on the applicable regulatory requirements, inventory objective and nature of industrial processes.
The draft identifies common pollutants such as:
- Particulate Matter – PM₁₀ and PM₂.₅
- Sulphur Dioxide – SO₂
- Oxides of Nitrogen – NOₓ
- Carbon Monoxide – CO
It also discusses hazardous and industry-specific pollutants, including VOCs, heavy metals and certain organic pollutants, depending on the industrial process.
Data Collection and Data Quality
Reliable data is a critical component of an emission inventory.
The draft provides for both primary and secondary data, with primary data preferred wherever practicable. Data should be source-specific and representative of the inventory period.
The proposed data hierarchy gives preference to:
- Direct monitoring data, such as CEMS or periodic measurements
- Plant-specific operational and production data
- Published literature or sector-specific databases
- Default emission factors or generalized estimates
Where lower-tier data is used, appropriate justification should be provided.
For area and fugitive emission sources, the draft proposes collection of activity data using a grid-based matrix, with grid size determined according to the industrial processes and spatial extent of the industrial area or cluster.
Proposed Emission Estimation Methods
The draft identifies three principal approaches for estimating emissions:
1. Direct Measurement Method
This approach uses actual monitoring data, such as pollutant concentration and exhaust gas flow rates.
The methodology discusses monitoring locations, measurement planning, instrumentation and calibration, sampling, data correction, emission calculation and data validation.
2. Emission Factor Method
Where direct monitoring data is limited, emissions may be estimated by applying appropriate emission factors to activity data.
The draft recommends considering factors such as:
- Process characteristics
- Fuel type
- Raw materials
- Operating conditions
- Pollution control systems
- Control efficiency
Preference is given to India-specific emission factors, where available.
3. Material or Mass Balance Method
This method estimates emissions based on the conservation of mass within a defined process or facility boundary.
Inputs, outputs, accumulation and unaccounted losses are considered to estimate potential emissions. The draft also requires assumptions, calculation steps, analytical data, uncertainties and limitations to be documented.
Accounting for Pollution Control Measures
The proposed methodology also considers the performance of existing Air Pollution Control Devices (APCDs).
Control efficiency may be based on:
- Manufacturer specifications
- Performance monitoring data
- Conservative assumptions where data is limited
The draft further notes that control downtime, malfunction, bypass, maintenance and operational variations should be considered where relevant while estimating net emissions.
Quality Assurance, Reporting and Documentation
A QA/QC plan should be established for the emission inventory.
The draft proposes activities such as:
- Data validation
- Plausibility checks
- Cross-checking calculations
- Comparison with historical data or benchmarks
- Assessment of uncertainty
The emission inventory report should provide information such as the study area, industrial activities, methodology, data sources, source-wise and pollutant-wise emission estimates, assumptions, limitations and uncertainties.
The minimum reporting content further includes source identification, process description, pollutants estimated, activity data, estimation method, calculated emissions and pollution control measures considered.
Periodic Updating of Emission Inventories
Industrial operations can change due to changes in production, technology, raw materials, fuels and other operational factors.
Therefore, the draft proposes that emission inventories should be periodically updated to reflect such changes. It also recommends maintaining a consistent methodology over time to enable meaningful emission trend analysis.
Illustrative Examples Included in the Draft
The proposed document contains illustrative examples demonstrating how the methodology can be applied.
These include:
- Direct measurement-based estimation
- Emission factor-based estimation
- Material/mass balance for SO₂ and SO₃
- Mass balance for solvent handling and VOC emissions
- Emission estimation for on-road vehicles
- Emission estimation for off-road vehicles and equipment
The draft clearly states that these examples are illustrative and that the numerical values used do not constitute normative emission factor values.
Important Note for Industries and Environmental Professionals
The proposed standard is significant for industries, environmental consultants, industrial clusters, research organisations, regulatory agencies and other stakeholders involved in environmental assessment and air pollution management.
However, it is important to note that this is currently a Wide Circulation Draft. The draft itself states that it does not prescribe emission limits, regulatory reporting formats or compliance requirements.
Stakeholders are invited to examine the document and submit comments for its further improvement. As per the BIS cover letter, comments are to be submitted through the prescribed template via the specified portal, with the last date for comments being 30 October 2026.
Conclusion
The BIS initiative to develop a “Methodology for Preparation of Industrial Emission Inventory – Code of Practice” represents an important step toward creating a consistent methodological framework for industrial emission inventories.
By providing guidance on source identification, data collection, emission estimation, pollution control measures, QA/QC, reporting and periodic updating, the proposed standard can help bring greater consistency and transparency to industrial emission assessment.
Industries and environmental professionals should closely review the draft and understand how the proposed methodology may affect future approaches to industrial emission inventory preparation and environmental data management.
GYE LLP can support organisations in understanding applicable BIS standards, environmental requirements and management-system related compliance requirements.
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