Overall the air pollution and resulting health impacts of thermal electricity generation in New Zealand is relatively small. One reason for this that most thermal generation uses natural gas. While natural gas generation can cause elevated levels of NOx, particulate emissions are generally very low.
Currently, the coal power plant at Huntly is the only large operational coal plant in New Zealand (some smaller co-generation facilities are operated by the industry sector and can run on coal) (Table D1). However, there are two coal stations in the initial planning and consenting phases in Waipara, Auckland and Buller, West Coast (Table D2). Some stations can, and do, operate on fuel oil (for instance New Plymouth and Whirinaki).
There are also eight geothermal power generations in New Zealand with a combined generating capacity of around 400 MW with another four plants in various planning stages. Geothermal plants emit approximately a third of the CO2 as would a power plant of the same capacity on gas, or about one-fifth that on coal. The main pollutants of concern resulting from geothermal power plants are hydrogen sulphide and mercury. Emissions of mercury are rarely sufficiently high to warrant monitoring, but are generally well below New Zealand guidelines. While hydrogen sulphide is toxic at high concentrations, geothermal emissions of H2S generally represent more of an odour nuisance than a health risk, and these emissions are not considered here.