5.1 Sector overview (CRF 3)
Solvents and related compounds are a significant source of emissions of NMVOC. Some solvents have been banned under the Montreal Protocol and there is an international trend away from solvent use in paints towards water-based (acrylic) paints.
This sector includes emissions from chemical cleaning substances used in dry cleaning, printing, metal degreasing and a variety of industrial and household uses. Also included are emissions from paints, lacquers, thinners and related materials. Emissions arise from the evaporation of the volatile chemicals when solvent based products are exposed to air.
Emissions from the solvents and other product use sector in 2004 comprised 31.94 Gg of NMVOC. This is an increase of 4.23 Gg (15.2 percent) from 27.71 Gg in 1990. The categories dominating the sector are NMVOC emissions from paint application and domestic and commercial use (Figure 5.1.1).
Gg CO2 equivalent
Percent of total
Degreasing and drycleaning
In 2004, N2O emissions from anaesthesia use totalled 0.16 Gg N2O or 48.36 Gg CO2 equivalent. This is a small increase on 1990 emissions from anaesthesia which totalled 0.13 Gg N2O.
Ethanol and methanol are the only solvents produced in New Zealand and the majority of both products are exported. All other solvents are imported, including some ethanol and methanol (due to quality and price reasons).
5.1.2 Methodological issues
The IPCC revised guidelines (IPCC, 1996) do not provide detailed methodologies for emissions from solvents and other product use. It does however document two basic approaches for estimating emissions: consumption and production-based estimates. The IPCC guidelines note that for many applications of solvents, the end uses are too small-scale, diverse and dispersed to be tracked directly. Therefore, emission estimates are generally based on total consumption and an assumption that once these products are sold to end users, they are applied and emissions produced relatively rapidly. For most surface coating and general solvent use, this approach is recommended. The New Zealand inventory estimates solvent emissions with a consumption-based approach. Information is obtained via a survey of industry and industry organisations (CRL Energy Ltd, 2006). Worksheets for the solvents and other products sector are included in Annex 8.3.
Emission factors are developed based on the likely ultimate release of NMVOC to the atmosphere per unit of product consumed. The emission factors are applied to sales data for the specific solvent or paint products. The four categories of solvents and other products specified in the CRF are detailed below.
Consumption and emissions from paints and thinners are based on information from Nelson (1992) and the Auckland Regional Council (1997). Additional information for 1993 to 1996 was provided by the New Zealand Paint Manufacturers Association.
Degreasing and dry cleaning
Most drycleaners in New Zealand use perchloroethylene and a few use white spirits. Trichloroethylene has never been used in dry-cleaning but it is used in degreasing, for instance in the leather manufacturing industry. In general, solvent losses from the drycleaning industry have reduced substantially as closed circuit machines and refrigerated recovery units are increasingly used. Consumption of perchloroethylene and trichloroethylene are assumed to equal the volume of imports. Import information is supplied by Statistics New Zealand.
Chemical products (manufacturing and processing)
The solvents tetrabutyl urea and alkyl benzene are used in the production of hydrogen peroxide. Emissions of NMVOCs are provided by the sole producer of hydrogen peroxide in New Zealand. The hydrogen-peroxide plant has an on-line, continuous, activated-carbon solvent recovery system. Solvent losses are recorded annually as the difference between input solvent and solvent collected for incineration.
Losses of ethanol (and other minor components such as methanol, acetaldehyde and ethyl acetate) are monitored in the three ethanol plants in New Zealand. Using these figures, an emission factor for NMVOC of 6 g/litre has been calculated. Ethanol used for alcoholic beverage production has been reported under food and drink production in the industrial processes sector.
Other - printing ink use
One major printing ink company with approximately 50 percent of the solvent ink market share provided a breakdown on the type of ink used. Approximately 50 percent of inks used are oil inks (paste inks) which contain high boiling temperature oils. These are evaporated off during "heat setting" but it is understood that the volatiles are generally treated in a solvent burner that minimises emissions. The remaining 50 percent of inks are liquid of which 60 percent are solvent inks (the remaining 40 percent are water based).
Other - aerosols
Approximately 25 million aerosol units are sold in New Zealand each year. Based on the assumptions that the units are fully discharged within two years of purchase, the average propellant charge is 84 grams and 95 percent are hydrocarbon based, total NMVOC emissions in 2004 were 1.9 Gg.
Other - domestic and commercial use
This category includes NMVOC emissions from domestic and commercial solvent use in the following areas: household products, toiletries, rubbing compounds, windshield washing fluids, adhesives, polishes and waxes, space deodorants, and laundry detergents and treatments. Emissions for this category are based on a per capita emission factor. The emission factor used is 2.54 kg NMVOC/capita/yr (USEPA, 1985). It is assumed that the emissions rate per capita derived by the United States Environmental Protection Agency (USEPA) is applicable to the average product use in New Zealand (CRL Energy Ltd, 2006). Population figures are from the Statistics New Zealand website.
N2O for anaesthesia
Activity data for 2004 was obtained from the sole importer of bulk N2O into New Zealand. The importer supplies its competitor with its requirements so the figure represents full coverage of N2O use in New Zealand. Most of the N2O is used for anaesthesia and the production of Entonox (a 50/50 mix of nitrous oxide and oxygen for pain relief). There is a very small amount used in motor sports and in scientific analysis.
5.1.3 Uncertainties and time-series consistency
Estimates of uncertainty are based on information provided by industry in the questionnaires and discussions with respondents (CRL Energy Ltd, 2006). The overall uncertainties are assessed to be:
- paint application: ±40 percent
- degreasing/drycleaning: ±30 percent
- chemical product emissions: ±20 percent
- printing, aerosols and domestic/commercial use: ±50 percent, ±20 percent and ±60 percent respectively.
- N2O for anaesthesia: ±10 percent for annual imports.
5.1.4 Source-specific QA/QC and verification
The consumption data from Auckland Regional Council (1997) and Nelson (1992) were compared to import data and discrepancies analysed and clarified by the consultant. There are considerable uncertainties and inconsistencies in applying the USEPA per capita emission factors based on international experience. Nevertheless, there is generally very little information available on New Zealand use of the various products and their consequent NMVOC emissions.
5.1.5 Source-specific recalculations
Data in this sector for the 2004 inventory are derived using the same method used for previously reported data. No changes have been made to the methodology.
5.1.6 Source-specific planned improvements
There are no planned improvements for this sector. There are large uncertainties, however the emission levels from the solvents and other products sector are negligible compared to other sectors. In accordance with Good Practice, New Zealand will continue to focus its inventory development on key source categories (IPCC, 2001).