Report: TR2006/05 

Author: Emily Wilton (Environet Limited), Jeff Smith (Environment Waikato), reviewed by Guy Coulson (NIWA)

Abstract

Reliable emission factors are essential for air quality practitioners as they underpin emissions inventories that are commonly used to identify sources and discharges of contaminants to air. There may be reliability issues with historical methods of establishing emission factors that involve either laboratory simulations of real life operation of burners or information from overseas research.

Under the National Environmental Standards for Air Quality (NES), AS/NZS4013 authorisation of low emission woodburners is required to verify, during laboratory testing, that less than 1.5 grams of particles are discharged for each kilogram of wood burnt (1.5 g/kg). While the authorisation limit is 1.5 g/kg, an emission factor of 3 g/kg is commonly used as an estimate of real life emissions for this group of appliances. However, recent research suggests that some low emission appliances may produce emissions that are substantially higher than the “real-life” emission factor of 3 g/kg.

The difference between laboratory and real life emissions may be because of variability of woodburner operation, installation characteristics or fuel type and quality in real life circumstances. Because this variability applies to woodburners of all ages, emission factors currently used for older woodburners are also uncertain. The objective of this investigation is to establish a real life emission factor for pre-1994 woodburners.

Twelve burners were selected for testing and each was monitored for at least seven days. The results indicate an emission factor of 10.4 g/kg is appropriate for pre 1994 wood burners and this is similar to particulate emission factors that are currently used for older burners in air quality management exercises. However, it is still uncertain what emission rates are appropriate for NES-compliant burners under real-life operation.

Real Life Emissions Testing of Pre 1994 Woodburners in New Zealand [PDF, 145 KB]