Impact on Standards
There are currently seven national ambient air quality standards as noted in Table V and others are being considered. The major emissions and their emission factors for woodburning stoves (WBS) and fireplaces are listed in Table VI. These emissions normalized to a hypothetical WBS particulate level in the ambient environment are compared with ambient standards in Table VII for an acute impact where WBS emissions are postulated as accounting for 260 pg/m3 of particulates. The standards which would be impacted most significantly are the 24-hr particulate standard (260 ug/ms), the 3-hr volatile hydrocarbon standard (160 ug/m3) and the carbon monoxide 8-hr standard (10,000 ug/m3). The 14-hr ambient particulate standard could be exceeded while the other impacts would be less than 50% of their respective standards. The volatile hydrocarbon standard would be the limiting standard for fireplaces, however, because of its tenfold greater volatile hydrocarbon emission factor.
Emissions from RWC sources appear even more significant, when compared to other fuels for residential space heating and transportation sources as shown in Table VIII. The different fuels are compared on the basis of lb emissions/million Btu gross energy output. This is an acceptable comparison for gas, oil, coal and WBS since their efficiencies are approximately equal. Fireplace efficiencies are at best 10% and typically much less. Their emissions, therefore, should be increased by about 5 to 10 times to make a valid comparison.
A typical winter heating load in Portland, OR for a single family residence is about 0.5 X 106 Btu/day which would require the combustion of about 106 Btu of wood based on a 50% wood stove efficiency. This clearly shows that residential solid fuels such as wood and coal emit between 10 and 1000 times more CO, benzo(a)pyrene, and particulates than other residential fuels. Wood-burning stoves emit about ten-fold more CO on a typical winter heating day than a typical highway vehicle would in a 50-mile trip. Gas and WBS emit much less SO,/Btu than either oil or coal which are about equal and strongly dependent on the sulfur content of the fuel. It is clear from this table that it will be difficult to regulate the use of coal independently from wood on the basis of any of the current ambient air quality standards other than the SO; standard. Perhaps this might take the form of a specification for the maximum sulfur content in coal as is currently done for oil. Although wood may replace some oil and coal, it will also replace some much cleaner fuels such as gas and electrical energy.
Table VII. Wood-burning stove emissions normalized to particulates compared to ambient air quality standards. Again, this table is omitted because the standards have changed since this paper was written in 1980.