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5 Conclusions

As part of the Warm Homes trial in Tokoroa, emissions from four pellet burners were tested in situ under real-life conditions. This has provided valuable information that has not been available before in New Zealand. Previously emissions data for wood-pellet burners has been based on laboratory results and overseas data.

The real-life testing revealed the presence of a pellet burner that was not working correctly. This meant that the data contained several outliers, which are probably not representative of the wider population of pellet burners. To account for this situation, means were calculated with and without the faulty burner. These were 3.9 g/kg and 1.4g/kg respectively. Air quality practitioners are recommended to make their own assumptions about the number of faulty pellet burners in the underlying population when preparing emissions inventories.

The Ministry recommends that the emissions factors for pellet burners calculated in this report be applied in air shed modelling because this represents the best available information on real-life emissions in New Zealand to date. However, as with all emission factors based on limited data, we advise exercising caution. It is important to take into account the small sample size, test methodology, faulty burners and narrow range of burner designs covered.