The use of estimation techniques is also a key aspect of a PRTR programme. Releases and transfers of pollutants are usually estimated rather than calculated through exact quantifiable measurements mainly because estimation is generally easier and less expensive. Different estimation methods are used depending on the industrial process, equipment and operating conditions at each factory or specific source.
The aim of this project is to help countries develop and implement PRTR systems by making the data about chemical releases and transfers easier to find and use. Since 2000, The Task Force on PRTRs has been developed a compendium of techniques used to estimate releases from various sources.
Four volumes of Resource Compendium have been published so far regarding point sources (2002), diffuse sources (2003), off-site transfers (2005) and releases from products (2011, Part I and Part II). The Framework for Selecting and Applying PRTR Release Estimation Techniques complements these Resource Compendiums by providing information on general principles for producing release data and the selection and application of the various release estimation techniques to different industrial sectors.
The Resource Centre for Release Estimation Techniques is also developed as a web-based clearinghouse of guidance manuals and other documents on release estimation techniques.