Estimating emissions of NMVOC from solvent and other product use

This report is the end product of a project revising the Norwegian emission calculations of NMVOCs¹ from the use of solvents and other products. The development of a new emission model started in 2007, and the results will be used for reporting from the year 2008.

According to international emission reporting guidelines, emissions shall be recalculated if new information about emission factors or improved calculation methods is available. The emissions of NMVOC from solvents and other product use were previously calculated using data on import, export and production of solvent-containing substances. The previous solvent balance was developed in 1995, and by the year 2000 the method was considered obsolete. It was thus decided to keep the emission estimates at the year 2000 level until a revised method was developed. A replacement of the solvent balance was due because the assumptions about solvent content and the emission factors were out of date.

The new model uses a new data source, namely the Norwegian Product Register. The data includes information on a substance level of the product type in which the substance enters into and the industrial sector in which the product is used (including private households). Because the data are given on a substance level, no assumptions about solvent content must be made. A list of substances satisfying the NMVOC criteria has been developed as part of the project, and these substances form the basis for the data selection from the Product Register.

The emission of NMVOCs to air is calculated by multiplying the amount consumed of an NMVOC by an emission factor. The consumption is expressed as the sum of production and import, minus export, declared to the Product Register. The emission factor represents the fraction of the substance emitted to air, and takes into account if a substance is incorporated in another product, transformed into a new compound, or handled in some other way (e.g. as waste). The fraction of an NMVOC emitted is dependent both on the type of product used and the industrial sector (including private households) in which it is used. The emission factors are specific for the combination of product type and industrial sector (including private households), and are mainly gathered from two Swedish reports.

The total NMVOC emissions in Norway was 199 000 tonnes in 2007, of which NMVOC emissions from solvent and other product constituted 48 570 tonnes. The use of solvents and other products was thus responsible for about 25 per cent of the total emissions. The lion's share of the emissions from solvents and other product use took place within the NFR²/CRF³ category "Other", which is NMVOC emissions from sources other than paint application, degreasing and dry cleaning and manufacture and processing of chemical products.

The new solvent model makes it possible to study emissions of NMVOC at a detailed level. The substance with the highest emissions in 2007 is ethanol, followed by hydrodesulfurized heavy naphta and ethylene glycol. Emissions were highest within construction, households, and sale, maintenance and repair of motor vehicles and motorcycles and retail sale of automotive fuel. The product types leading to the largest emissions of NMVOC were biocides, cleaning agents and degreasers, paint and varnish, and solvents.

International reporting requires the time series of NMOVC emissions to be consistent from 1989. The Product Register data were only deemed of sufficient quality from the year 2005, however, and the time series from the previous solvent balance was thus adjusted in order to obtain as much consistency as possible in the time series. This resulted in an elevation of emission estimates of between 3 500 to 5 500 tonnes per year for the years 1989 to 2004.

¹ Non-Methane Volatile Organic Compounds

² Reporting format in which emissions are reported to the Convention on Long-Range Transboundary Air Pollution (Gothenburg protocol)

³ Reporting format in which emissions are reported to the UNFCCC according to the Kyoto protocol

Conclusion

The new calculation method for emissions of NMVOC from solvents and other product use covers a wide range of substances and a wide range of industrial sectors and product types at a much more detailed level than the previous solvent balance. The coverage is deemed to be better for the new than for the previous model, and sufficient for reporting requirements. In addition, the new model makes no assumptions about solvent content in products, as the calculations are based on amounts of the substances deemed to be NMVOC. The new model is thus more accurate than the previous model.

Acknowledgements: This work was carried out in cooperation with Mette Follestad (the Norwegian Product Register), Jan Kraft (the Norwegian Product Register) and Kathrine Loe Hansen (Statistics Norway). The uncertainty analysis was performed by Marie Lillehammer (Statistics Norway).

The project received financial support from the Norwegian Pollution Control Authority (SFT). Eilev Gjerald and Hans Kolshus at the Norwegian Pollution Control Authority made important consultative contributions during the work process.