Primary energy includes the use of coal, natural gas, electricity and oil.
The MED’s on-line energy data16 records coal use amounted to 86 PJ/year, or 3.88 Mt in 2008. The biggest use was for the generation of electricity at 1.96 Mt (predominantly at Huntly Power Station, although coal is used in a small way to generate electricity as part of industrial co-generation).
MED (2006) assumed that Huntly Power Station would be using 18 PJ of coal for most of the period from 2005 to 2020. The actual recent use of coal at Huntly Power Station is currently considerably greater. If Huntly Power Station consumed 92% of the coal used for electricity in 2008, then its actual coal use would equate to 40.6 PJ (Section II-3.2.1).
The actual use of coal at Huntly Power Station over the next few years is difficult to predict as it depends on the availability and price of gas as an alternative fuel at Huntly and the price and availability of competing power generating capacity. The conservative position is to assume that Huntly Power Station continues using about 2 Mt /year and otherwise use the MED (2006) forecasts to increase the other coal uses. For non-electricity uses this amounted to about an 8% increase over ten years. Applying this to the mercury emission calculations from Section II‑3.2.1 (of 237 kg Hg/year) would result in mercury emission of approximately 260 kg.
It should be noted, however, that the EC (2008) in its forecasts assumes that Huntly Power Station will generate less electricity in ten years time than now in four out of the five scenarios it modelled. In these four scenarios, Huntly was assumed to continue generating with coal at a high level for the next few years but reduce to about half by 2018. Both MED (2006) and EC (2008) assume there will be no new coal-fired generation within the next ten years.
Not accepting the EC (2008) assumption of reduced generation at Huntly is inconsistent with also accepting its scenarios of increased gas and geothermal generation (with associated increases in mercury from these forms of generation). Thus, the above estimate for Huntly is conservative by about 100% (the equivalent of about 1 million tonnes of coal) and a better estimate for Huntly in ten year’s time is 130 kg of mercury. In 2008 Huntly made up 92% of coal-fired power generation, with the balance being industrial co-generation. Mercury emissions from other generation are estimated to have been 21 kg in 2008. If this amount is assumed to remain unchanged over the next ten years, the total mercury emissions for coal-fired power generation in 2018 would be 151 kg Hg/yr.
As noted earlier in this report, the main non-power station uses of coal are in steel manufacture, cement and lime manufacture, the dairy industry, the meat industry and other uses. The largest use of coal after Huntly is the Glenbrook steel plant. The future emissions from Glenbrook are considered under the primary metals production sector in Section IV-3.2. Future emissions from cement and lime manufacturing have also been specifically calculated in Section IV-3.3.
For the dairy sector, MED (2006) assumed that cow numbers would increase by 1% per year and therefore coal use would do the same, or about an 11% increase over ten years. However, the Ministry of Agriculture and Forestry, in its 2008 outlook document (MAF, 2008), suggests dairy herd increases of 2 – 3% per year for the next few years. This may not be sustainable for the next ten years, but if the lower figure is taken and it is assumed milk production and coal use increases at the same rate, then the current dairy sector mercury emissions from coal will increase 22% from 39 kg Hg/yr to about 48 kg Hg/yr.
MAF (2008) is pessimistic about the meat industry growth, with sheep numbers declining and beef numbers stable. Based on this it is assumed the meat sector coal use stays static over the next ten years. In other words, the current 16 kg Hg/yr remains unchanged. This leaves other industrial users, with a current emission rate of 7 kg Hg/yr. If it is assumed coal use increases at the assumed rate of GDP increase, i.e. 28%, emissions will increase over ten years from 7 to 9 kg Hg/yr.
The MED’s projected fuel oil (petrol and diesel) demand in New Zealand use amounted to 288.97 PJ/year in 2008 (MED, 2006). The MED forecasts that this figure will increase to 340.94 PJ in 2018. In 2008, approximately 70% of the fuel oil used in New Zealand was refined at the Marsden Point refinery and about 30% of the fuel oil was imported into New Zealand as refined product (NZRC, pers. com, 2009).
To estimate the amount of mercury generated from oil in 2018, the following assumptions have been made:
The 10-year mercury forecast based on these assumptions is 83 kg Hg/yr from approximately 7,400 million litres of petroleum products.
The EC has recently produced a new forecast for natural gas use (EC, 2009) as part of its forecasting for electricity generation. This has been used in preference to early forecasts by MED (2006).
The EC used Monte Carlo simulations to predict gas use for a number of different scenarios, based on current gas production and known reserves, with different assumptions for such things as future gas use, gas imports and new finds of gas in New Zealand. Gas use is very difficult to predict given the unknowns with respect to future prices, government policy on measures to limit greenhouse gas emissions (which affects price), price-sensitive competing uses for gas, and future production in New Zealand.
Taking EC’s “Medium gas production forecast” 50th percentile prediction as a reasonable average, gas use is predicted to decrease from around 170 PJ in 2008 to about 125 PJ in 2018. This translates to a decrease in mercury emissions from 60 kg/year (Section II-3.2.1) to 48 kg/year.
The MED (2006) forecasts predict an increase in biomass energy use between 2005 and 2020 of 10%. On a pro rata basis, the 10-year increase from 2008 would be about 7%.
The majority of biomass energy use is home heating. Increasing the mercury emissions from use of wood from home heating in Section II-3.2.1 by 7%, results in an increase of mercury emissions to 11 kg Hg/yr in 2018.
Geothermal power generation has been forecast by the EC (2008). Using the "Medium Renewables Scenario" (as an “average” scenario, but all scenarios are similar for geothermal power), EC (2008) predicts about a 190% increase in geothermal generation. Taking the current mercury emissions estimate of 350 kg Hg/year (Section II-3.2.1 ) and multiplying by 2.9 results in 1020 kg Hg/year in 2018.
The current contributors to mercury emissions in the primary metal sector are gold mining and steel production. The major contributor is steel production, the majority of which is expected to be from use of coal.
Glenbrook steel mill is currently running at close to capacity. There are no known plans to expand the current capacity and lead times for expansion are relatively long. On that basis it is assumed that mercury emissions will be the same in ten years, that is, 26 kg Hg/yr.
Emissions from gold production are relatively small; less than the error estimates from other sources. No information exists on what gold production may be in ten year’s time. The mining at Waihi has known reserves that will take mining through to 2011, but active exploration is continuing and the mine’s life may be extended17.
New Zealand’s other major gold mines are operated by Oceana Gold. The 2008 Oceana Annual Report (Oceana, 2008) states the mines have a further operational life of five years. However, exploration is on-going.
On the basis of current information, gold production will decrease and therefore mercury emissions will decrease. However, given the uncertainties, it is assumed gold production will remain static for the next ten years.
Section II-3.2.3 provided estimates of current emissions from the cement and lime industries.
The primary source of emissions from the cement and lime industries is from the use of coal in the manufacturing process.
The current Holcim plant in Westport is running at capacity. Holcim is planning to build a new plant at Weston in North Otago to replace their Westport plant. This will have a larger capacity than the current plant and therefore use more coal. However, in information provided with the Weston resource consent application, Holcim predicts an annual increase in cement use of 1.5%, and presumably a coal use increase of similar magnitude. The consent application reported18 that the plant was expected to emit around 0.0018 kg of mercury per hour, based on an annual usage of coal of 190,000 tonnes, the average mercury content of the coal to be used and assuming 40% of mercury being emitted. This translates to about 18 kg Hg/year for the plant running 24 hours per day. This compares with about 3 kg Hg/year for the current Westport plant.
The Weston plant will have a capacity of up to 790,000 tonnes of clinker per year, which equates to a mercury emission rate of 0.022 g/tonne, which is higher than the reported Westport emissions of 0.007 g/tonne, but similar to Holcim's international average (Section II-3.2.3). The UNEP (2005) default is 0.1 g/tonne. An annual increase of 1.5% is the equivalent of a 16% increase after ten years. Increasing Holcim’s current production by 16% and applying an emission factor of 0.022 g Hg/tonne translates to 11.7 kg Hg/yr. Similarly, taking the current emission estimate for Golden Bay Cement and increasing by 16% results in an emission rate of 11.6 kg Hg/yr. Combined, the projected total for 2018 from cement manufacturing is about 23 kg Hg/yr, compared with the current estimate of 13 kg Hg/yr.
There are no forecasts on the amount of burnt lime production in New Zealand, however, using the data in the MfE (2009) New Zealand Greenhouse Gas Inventory 1990-2007 it is possible to extrapolate the amount of lime that might be produced assuming that the increasing rate of lime production between 1990-2007 is continued to 2018 (Figure IV-1). Using this assumption, approximately 210,000 tonnes of lime is expected to be produced in 2018, which would equate to mercury emission rate of approximately 1.9 kg/yr or a 35% increase on the 2008 emission rate (Section II-3.2.3).
Figure IV-1 Projection for burnt lime production in New Zealand to 2018
Illustrated as a line-graph of date in years from 1995 to 2025 and burnt lime production in hundred thousand of tonnes.
The graph shows an exponential growth in burnt lime production over time from a 1990 figure of about 118,000 tonnes to a 2005 figure of 180,000 tonnes. Using the assumed increasing rate of 1.9kg/yr, the graph shows approximately 210,000 tonnes of burnt lime is expected to be produced in 2018.
18 Reported in the resource consent application decision of independent hearings commissioners appointed by Otago Regional Council and Waitaki District Council , available at: http://www.orc.govt.nz/Documents/ContentDocuments/resource_consents/Feb_2008/Final%20Dec%20Feb%2008.pdf (PDF, 4 MB)