From 1996 to 2013, the number of households that burnt wood or coal for home heating decreased 25 percent.
Home-heating and air quality
Burning wood or coal for heating homes emits many pollutants, including PM10, carbon monoxide, sulphur dioxide, benzo(a)pyrene, and arsenic (if treated timber is used). Nationally, burning wood or coal for home-heating is the main source of human-made PM10 emissions (Kuschel et al, 2012).
Home-heating generally occurs during May to August and so does not affect air quality throughout the year.
Nearly all exceedances of the national environmental standard for PM10 (94 percent from 2010 to 2012) occur during the cooler months. These exceedances are due to:
- increased emissions from burning wood or coal for home heating, which accounts for 90 percent of human-made winter-time PM10 emissions in some areas of Waikato, Hawke’s Bay, Nelson, Canterbury, Otago, and Southland (Airshed progress reports provided by regional councils to the Ministry for the Environment for compliance reporting)
- the increased incidence of weather conditions that prevent dispersal of pollutants, such as low wind speeds and temperature inversions.
Case study: Fewer households are burning wood or coal for home heating:
The number of households burning wood or coal for home heating decreased 25 percent from 1996 to 2013. Approximately 788,000 dwellings (or 62 percent of all dwellings) burnt wood or coal for home heating in 1996, reducing to 594,000 dwellings (38 percent of all dwellings) in 2013 (see figure 25). Data sourced from Statistics NZ’s 2013 Census.
Between 1996 and 2013, the number of households burning wood for home heating fell 12 percent (from approximately 622,000 dwellings to 546,000), while those burning coal fell 71 percent (from approximately 166,000 dwellings to 49,000). This decrease occurred despite a 22 percent increase in the number of households in New Zealand.
Burning wood or coal for home heating is the key source of New Zealand’s PM10 concentrations during the cooler months (Kuschel et al, 2012). The decrease in homes burning wood or coal has likely resulted in a decrease in emissions from home heating, which is likely to have led to lower PM10 concentrations from 2006 to 2012. The rate at which wood burners are being replaced by newer more efficient appliances is unknown but will likely result in a further decrease in emissions from home heating. Other factors, such as quantities of wood and coal burnt also affect emissions.
This graph shows households burning wood or coal for home heating 1996–2013 Censuses. Visit the data files page for the full breakdown of the data.
Despite reductions in the number of households burning wood or coal for home heating, it still causes high levels of PM10, PM2.5, arsenic (due to burning treated timber offcuts), and benzo(a)pyrene in some locations (see the state of New Zealand's air section of this report for more information).
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Home-heating is the main source of PM10 in most urban areas
Studies by some councils (Auckland, Waikato, Hawke’s Bay, Manawatu-Wanganui, Wellington, Marlborough, Nelson, Tasman, Canterbury, West Coast, and Southland) showed that home-heating using coal or wood is the main source of PM10 in most urban locations – particularly in winter (Airshed progress reports provided by regional councils to the Ministry for the Environment for compliance reporting).
Many factors influence people’s home-heating choices, such as how cold the winters get, local regulations on options for home heating, and the ease of access to and the cost of wood, coal, or other heating sources. These factors can result in differences in the number of appliances, and likely emissions, at the local level (see figure 26 to see home-heating using coal or wood by area).
Figure 26: Home-heating using wood and coal burners, by area 2013
Source: Data provided by Statistics New Zealand
This image shows home-heating using wood and coal burners, by area 2013