Volume 15, No. 6, November 2015, Pages 2346-2356 PDF(784 KB)
An Investigation of the Variability of Particulate Emissions from Woodstoves in New Zealand
Guy Coulson, Richard Bian, Elizabeth Somervell
National Institute of Water and Atmospheric Research, Private Bag 99940, Auckland 1149, New Zealand
- Seven in-situ woodstove emissions measurement campaigns in New Zealand reanalysed.
- All show log-normal distribution as does combined dataset.
- No correlation between co-efficient of variance and sample size.
- Emissions are inherently variable.Emission factors 9.8 (± 2.4) g kg–1 (older stoves) and 3.9 (± 3.8) g kg–1 (low-emission).
Woodburning is the dominant source of PM10 in most of New Zealand, and the principal cause of exceedances of the national air quality 24-hr standard (50 µg m–3). Over the last decade New Zealand researchers have used multiple techniques to characterise woodstove emissions, including seven campaigns to measure real-life PM10 emissions from in-situ woodstoves. All measurements have shown considerable variation, both within and between campaigns. PM10 emission factors from in-situ tests exhibit a log-normal distribution with a geometric mean (± standard deviation) of 9.8 g kg–1 (± 2.4 g kg–1) and 3.9 g kg–1 (± 3.8 g kg–1) (dry wood) for older and low-emission stoves respectively. Since the distribution is log-normal we recommend the use of geometric mean rather than arithmetic mean as the emissions factor used for inventories. This paper examines the variability of PM10 emissions from woodstoves using a Kernel Density Estimate to compare the distributions within and between campaigns and correlations between coefficients of variations (c.v.) to see whether the variation in emissions factors could be reduced by the collection of further measurements to increase the size of the total dataset. We conclude that variation in emissions is inherent in the way woodstoves are used in real-life and that regulators will need to allow for a range of emissions in management plans as a definitive emission factor may not be possible.
Woodsmoke; PM10; Emission factors.