ENVIRONMENTAL IMPACT OF RESIDENTIAL WOOD COMBUSTION EMISSIONS AND ITS IMPLICATIONS

John A. Cooper
Oregon Graduate Center
Beaverton, Oregon

Currently available information suggests a substantial environmental impact from residential wood combustion emissions. Air pollution from this source is widespread and increasing. Current ambient measurements, surveys, and model predictions indicate winter respirable (<2 pm) emissions from residential wood combustion can easily exceed all other sources. Both the chemical potency and deliverability of the emissions from this source are of concern. The emissions are almost entirely in the inhalable size range and contain toxic and priority pollutants, carcinogens, co-carcinogens, cilia toxic, mucus coagulating agents, and other respiratory irritants such as phenols, aldehydes, etc. This source is contributing substantially to the nonattainrnent of current particulate, carbon monoxide, and hydrocarbon ambient air quality standards and will almost certainly have a significant impact on potential future standards such as inhalable particulates, visibility, and other chemically specific standards. Emission from this growing source is likely to require additional expenditures by industry for air pollution control equipment in nonattainment areas. _

Man has been exposed to a large number of complex and hazardous chemicals from forest and domestic fires throughout his evolution. Thus, environmental concern over increasing use of wood as a residential energy source is not exposure to a new form of air pollutant, but is, instead, concern over the level of exposure and its impact on public health, current and future ambient air quality standards, and industrial growth. Increasing costs of energy, decreasing availability of fossil fuels, and government encouragement will assure the continued growth of this source of pollution over the next few years. This dramatic shift in energy utilization, however, is being encouraged without an adequate understanding of either the environmental impact or the total costs and benefits. Our forests and their wood wastes are a vital national resource and their use for single family residential space heating is just one of many possible options. The environmental impact is an essential component in the cost-benefit analysis and effective decisions relative to the use of this source of building materials, chemicals, and energy will require an accurate understanding of their impact on the environment.

Currently available information on the impact of residential wood combustion (RWC) sources on air quality is minimal and previously available impact assessment methods inadequate. Recently developed and applied assessment methods using chemical mass balance (CMB) and carbon-14 measurements by Cooper, et al.(1-3) have shown promise of improving our understanding and impact assessment capabilities. The primary objectives of this presentation are to review the available information on potential environmental impacts, note areas where conflicts are likely, and suggest areas of future research.

Use Trends

Increased energy costs and the availability of wood over a large part of the country has stimulated a rapid increase in the use of RWC devices for space heating in the last few years.(1-4) Coal and wood were the predominant fuels available for residential heating in the U. S. before the twentieth century. Near the turn of the century gas and oil became available and signaled the decline of coal and wood use for home heating. This decline in the use of wood was rapid from 1940 to the early 1970's as the population shifted to urban centers and gas, oil, and electricity for heating. This decline continued until about 1973 when the oil embargo occurred. Since then, the use of wood was increased dramatically. The number of stove-type residential heating units shipped in 1972 was about 228,000, but jumped to about 603,000 units by 1975(4-6) and are expected to be about one million in 1979 as illustrated in Figure 1. A large number of these units, however, are being installed in major metropolitan population centers and this trend is likely to continue with the increasing costs of fossil fuels. In addition, the use of already installed RWC units will be extended from secondary to primary heat sources, for heating over a greater portion of the heating season and to include the heating of water. New uses such as trash incineration and coal combustion may also develop.

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