Emissions from residential wood-burning heaters : a study of the problem, its measurement and control, and the determination of some emission factors

In Australia there has been a sharp increase in residential wood-heating since the late 1970s, and the trend is expected to continue for some years. Overseas research has shown that, under certain conditions, wood-heating can be a source of serious air pollution problems. The particulates resulting from wood-burning appliances are primarily organic in nature and, being in the respirable size range, can cause a variety of health ailments including cancer. The reaction of affected communities overseas has been varied. New Zealand followed the British example by allowing Christchurch to be declared a Clean Air Zone, but the results are not comparable to those achieved in Britain. In the United States, the Environmental Protection Agency has proposed a new source performance standard for wood-burning appliances which will become effective in July 1988. However, a number of control measures are already in force in several states and towns. In Europe, voluntary performance certification of appliances occurs in the Netherlands and Switzerland; and fire insurance premiums are linked to regular inspections and maintenance in France. In Australia, there is currently no co-ordinated control strategy to deal with this potential problem. Only the New South Wales Clean Air Act gives limited powers to local councils. Recently some brochures on wood-heater smoke reduction have been published and are available in some states. A standard measurement technique is of vital importance in controlling pollution. In wood-heater applications this has been lacking and the task of its development is made difficult by the non-discrete nature of the particulates in wood-smoke as well as the variations in the wood-burning process. An assortment of methods have been used to measure particulate emissions from wood-heaters. Oregon Method 7 was the first \standard method\" for this source and is a modification of EPA Method 5. The ASTM has proposed a dilution tunnel method which is finding popular support; it has been accepted by the New Zealand Clean Air Council as the \\Standard Method and also by the US EPA. Another dilution method is the Condar Method which has been accepted by the Oregon DEQ as equivalent to OM-7. This is a very simple and relatively inexpensive method which can identify periods of high emissions during a burn. This method was used in the experimental part of this study. Seventy three tests were conducted on two models of heaters (one catalytic and the other non-catalytic) using three types of fuel wood and varying fuel loads and burn rates. Statistical analysis revealed no difference between the catalytic and the non-catalytic models and no effect of varying burn rates on emissions; emissions increased with larger fuel loads for one fuel wood type whereas for the other two types there was no significant increase. Correlations between particulate emissions and average flue gas concentrations of 02 co2 and CO were very poor. Particulate emission factors obtained during the experimental programme ranged from 0. 4 to 32. 7 g/kg (0. 9 to 56 .1 g/h) with an average of 8. 2 g/kg (15 .1 g/h) for eucalypt firewood. Lower emissions were obtained for eucalypt and pine brands; with eucalypt brands the range was 0.4 to 4.4 g/kg (0.9 to 13.9 g/h) with an average of 1.8 g/kg (4.4 g/h) whereas for pine brands the range was 1.3 to 5.5 g/kg (2.6 to 13.5 g/h) with an average of 3.3 g/kg (7.2 g/h). On the basis of this study it is recommended that detailed studies be initiated to estimate the impact of this source on ambient air quality in the areas where wood-burning is popular. This should then lead to the formulation of an appropriate control strategy. Meanwhile greater importance should be given to public education programmes."