Clause 15 of the NPI NEPM requires occupiers to use the estimation techniques in the published industry reporting materials, or another technique the jurisdiction agrees is likely to be more representative. The occupier must document any alternative technique it uses and keep the data needed to verify its estimates for the period its jurisdiction requires.
Key points
- Clause 15 of the NPI NEPM governs estimation techniques
- Four standard techniques, from mass balance to emission factors
- 94 industry EET manuals, used with the NPI Guide Version 6.1
- Alternative techniques need written agency approval
- Verification data must be kept and alternative techniques documented
The four standard techniques
- Mass balance, tracking inputs and outputs of a substance through a process.
- Fuel analysis or engineering calculation, using fuel composition or process chemistry.
- Sampling or direct measurement, including continuous emission monitoring systems.
- Emission factors, relating the quantity emitted to a unit of activity, graded from A (excellent) to E (poor) or U (unrated).
Where the methods are published
DCCEEW lists 94 approved EET manuals by industry sector, including mining, combustion in boilers, combustion engines, fuel and organic liquid storage and explosives detonation. They are used together with the NPI Guide, currently Version 6.1. Excel calculation tools based on the manuals work offline or with the Online Reporting System.
Using a different method
Alternative techniques, such as predictive emission monitoring, need written approval from the state or territory agency before the report is submitted. Estimates made with a published or approved technique are shown as having acceptable reliability in the NPI database. Where no EET exists for an activity, the facility should contact its state or territory NPI team.
State rules on choosing a technique
Some jurisdictions add their own rules. In New South Wales the occupier must choose the technique likely to be most reliable, and an application to use an alternative is taken to be refused if the EPA has not decided within 90 days.
Why it matters
The technique chosen can change a reported figure substantially, and a change of method between years can appear in the public data as a change in pollution. Recording why a technique was chosen, and noting any change in method, helps readers and regulators interpret year-on-year movements.
References & sources
Primary regulatory documents and authoritative references underpinning this answer.