Set the boundary before collecting data
The inventory should document the organisational boundary, operational boundary, reporting period and consolidation approach. Without this, the organisation may collect large volumes of data yet remain unable to explain which entities, branches, vehicles, generators, leased assets or value-chain activities are included.
A source register should identify every relevant emission source, its scope, data owner, activity unit, collection frequency, evidence and calculation method.
- Scope 1: owned or controlled combustion, vehicles and fugitive emissions
- Scope 2: purchased electricity, steam, heat or cooling
- Scope 3: relevant value-chain categories such as travel, procurement, waste and financed emissions
Activity data must retain context
A number without a period is not useful. One thousand litres of diesel may represent one week, one month or six months. Every record should therefore retain period start, period end, location, source, unit and supporting evidence.
Controls should reject incompatible units and prevent conversion from being hidden from the reviewer. Where energy content is required for a calculation, the system should preserve the original litres and show the conversion method rather than replacing the activity value with terajoules.
- Electricity in kWh
- Diesel and petrol in litres
- Refrigerants in kg by gas type
- Waste in kg or tonnes by treatment route
- Travel in passenger-kilometres or route/class data
Govern emission factors
Emission factors are not universally interchangeable. Selection depends on the activity, geography, technology, reporting year, gas coverage and calculation method. The library should record publisher, source reference, version, validity period, unit basis, scope category and global warming potentials.
Nigeria-specific grid factors should be used where authoritative and appropriate. International factors such as IPCC fuel combustion methods or recognised travel and waste datasets may be used where local factors are unavailable, with the choice disclosed.
- Version-controlled factor library
- Review and approval before use
- No silent replacement of historical factors
- Transparent factor provenance in calculation records
Connect calculation to assurance
Each calculated emission should trace back to approved activity data, evidence and the exact factor version. Review should test completeness, duplicates, unit conversion, period allocation, factor choice and reconciliation to utility, procurement or financial records.
The resulting inventory should explain recalculation policy, exclusions, estimation, uncertainty, methodology changes and performance against targets. That is what turns a carbon figure into decision-useful and assurance-ready information.