Section IV – Ten-year Projections of Mercury Loadings:
2 Methodology
A variety of methods have been used to calculate forecasts for anthropogenic emissions in ten year’s time (2018 using 2008 as the baseline). In some instances industry estimates have been used, e.g. for CFLs sales into the future. However, a large part of the anthropogenic emissions calculated in Section II are for emissions associated with energy use in New Zealand. Prediction of New Zealand’s energy use are therefore required to project mercury emissions into the future.
A number of official forecasts exist for energy use into the future. These include modelling by the Ministry of Economic Development to predict energy use through to 2030 (MED, 2006) and the Electricity Commission forecasting locations and types of electricity generation for planning electricity grid upgrades (EC, 2008, 2009). These reports have been used, together with supplementary information, to forecast future coal, natural gas and transport fuel use and to predict geothermal electricity generation. Later forecasts have been used in preference to earlier forecasts, where they contain similar information.
The MED Energy Outlook 2030 report (MED, 2006) considered energy use by sector (e.g. residential, commercial, heavy industrial, electricity generation) and fuel type (oil, gas, coal, geothermal) using 2005 as the baseline. Where GDP was used to forecast future growth in this document, New Zealand Treasury predictions were used for the five years between 2005 and 2010 followed by a linear decline in GDP growth from 2.6 to 2% from 2010 to 2020. It is necessary to examine these assumptions in the light of recent economic performance and the possibility of a prolonged economic downturn. These could affect the validity of the MED (2006) predictions.
Treasury has recently updated their quarterly economic forecast for the next five years (Treasury, 2009). These forecasts together with GDP statistics from Statistics New Zealand13 were used to assess the validity of the MED (2006) GDP forecasts.
A comparison is set out in Table IV-1. The updated forecasts uses the actual GDP increases for the period 2005 – 2008, the treasury forecasts for 2009 – 2013 and the long-term average between 1988 and 2008 (2.7%) for the period 2014 – 2018. It can be seen that while the MED (2006) forecasts slightly over-predicted actual performance for the period 2005 – 2008, for the period 2009 – 2018 it is more pessimistic than the updated forecasts, mainly because the long-term increase MED has used is less than the long-term average to date. The overall increase from 2005 – 2018 is very similar and therefore it seems reasonable to use the MED (2006) forecasts to predict increases in energy use for the period from 2008 to 2018, in the absence of better information. However, where later information has been available, this has been used.
| Period | MED (2006) | Updated forecast | ||
|---|---|---|---|---|
| Cumulative | Average | Cumulative | Average | |
| 2005—2008 | 9.2 | 3.0 | 8.2 (actual) | 2.6 |
| 2009—2018 | 26.8 | 2.5 | 28.2 | 2.4 |
| 2005—2018 | 38.6 | 2.5 | 38.4 | 2.5 |
In calculating the 10-year forecasts, it has been assumed that emission factors applicable to the current situation will be the same, that is, there will be no improvement in technology to improve the capture of mercury emissions following combustion. This assumption is conservative.
Some of the mercury emission projections in this section have been calculated based on expected population or household number increases to 2018. Statistics New Zealand provides such estimates. It is expected that New Zealand’s population will increase around 9% from 2008 to 2018 (Statistics New Zealand, 2009)14, and household numbers will increase around 14.3% (Statistics New Zealand, 2009)15. Population and household number increases have been used to project the emissions from some of the consumer products with intentional use of mercury (Section IV-5). Further information on the derivation of 10-year predictions is outlined in the individual sections.
A summary of the 10-year predictions is compiled at the end of the section, followed by an assessment on whether the relative contribution of mercury from mercury-containing lamps will change significantly over the next ten years when compared to New Zealand’s anthropogenic load, and overall mercury load. In this study, the natural mercury emissions in ten year’s time have been assumed to be the same as that assessed for 2008.
This may or may not be true depending on whether there are any volcanic eruptions over the next ten years. Volcanic eruptions have the potential to completely overshadow New Zealand’s current mercury load. With the remaining natural sources, geothermal emissions are expected to remain constant over time, while volatilisation of mercury from soils may increase. The latter is due to a gradual increase in airborne concentrations of mercury over time, which when deposited, will lead to slight increases of average soil concentrations. This increase cannot be quantified and, given the slow increase in atmospheric concentrations, is not considered significant.
14 Projected Population Characteristics, 2006 (base) – 2061. Sourced from http://wdmzpub01.stats.govt.nz/wds/TableViewer/tableView.aspx?ReportName=Population%20Projections/Projected%20Population%20Characteristics,%202006%20(base)%20-%202061. Series 5 (middle) predictions have been used.
15 Projected households by household type, 2006 (base) – 2031. Series 5 (middle) predictions have been used.
http://www.stats.govt.nz/browse_for_stats/population/estimates_and_projections/nationalfamilyandhouseholdprojections_hotp06-31projections.aspx
