A dialogue with one of our well-informed visitors

Dear woodheat.org:

I am an environmental engineer and an air quality consultant. My initial opinion is that open wood-burning fireplaces should be outlawed, or at least governments should provide incentives to homeowners and builders to install alternative "clean" technologies.

Following is my summary of the environmental impacts of modern wood burning space heaters. I would sincerely appreciate your comments on each issue so that I can better understand the issues and better advise my clients and friends.

First the good news:

1) Wood Heaters Reduce Global Warming! Combustion of fossil fuels is the overwhelming cause of increased carbon dioxide in the atmosphere, and carbon dioxide is the primary cause of global warming. Trees absorb carbon dioxide from the atmosphere, and by photosynthesis, release oxygen and store carbon in the wood. When wood is burned, the carbon dioxide is re-created and released into the atmosphere. This is the same amount of carbon dioxide that would be released should the tree die and rot on the forest floor. This is the known as the “carbon cycle” and is environmentally neutral. Wood heaters reduce Global Warming because they displace carbon dioxide that would otherwise have resulted from burning fossil fuels (i.e., coal, oil, propane, or natural gas).

2) Wood Heaters Reduce Acid Rain! Combustion of fossil fuels is the overwhelming cause of anthropomorphic (man caused) NOx and SOx in the atmosphere. These compounds react in the atmosphere to create nitric and sulfuric acid, which fall to the earth as acid rain. Wood heaters generate less NOx and SOx emissions than fossil fuel burners (i.e., coal, oil, propane, or natural gas).

3) Wood Heaters Reduce Smog! Smog (ground level ozone) results from complex reactions of NOx and VOC and sunlight in stagnate air. Wood heaters generate less NOx and VOC emissions than burning fossil fuel (i.e., coal, oil, propane, or natural gas).

4) Wood Heaters Reduce Fuel Use! Central heat is a huge waste of fuel. Using modern wood stoves to heat only the spaces that are occupied reduces fossil fuel consumption by 40% in an average American home. This reduction in fossil fuel usage further reduces Global Warming, Acid Rain, and Smog. In many homes, the reduction in fuel usage also saves money.

Then the bad news:

5) Wood Heaters Increase Particulate Pollution! Modern wood heaters generate only a fraction of particulate (smoke) emissions as open fireplaces and obsolete wood heaters. However, even a properly operated modern wood heater generates four times the particulate emissions than oil combustion  and ten or more times the particulate emissions than natural gas combustion.

6) Wood Heaters Increase Toxic Air Pollution! The amount and toxicity of the hazardous components in wood smoke is hotly contested. Some compare it to cigarette smoke and breathing diesel exhaust. Others claim the toxic emissions from a modern wood heater are similar to emissions from burning fossil fuels. Seems both sides can find credible data to support their positions. However, there is little doubt that burning treated wood, waferboard, plastic, styrofoam, and other “unauthorized” material has the potential to create significant toxic air pollution.

Bottom line is - I am considering installing and using a modern EPA certified wood heater insert into my own seldom-used open fireplace. Friends and family see me as an environmentalist and may follow my lead. Is this the "right" thing to do?


Hi Clyde,

Thanks for your note. The analysis you use to weigh the pros and cons of choosing wood fuel is a good example of what we would encourage everyone to employ in their energy decision making. Sadly, such an objective is not realistic given the low level of energy literacy among most North Americans. The dominance and control of the energy production industries and those manufacturing for the consumption side (automotive), and with the active support of government, effectively prevent energy users from learning about the cause and effect relationships that result from their choices. We think the act of using wood fuel helps people get closer to the realities of energy production and consumption.

I think your analysis is generally good, but I do have a couple of comments.

Open fireplaces are certainly a major problem for at least three reasons: as a source of outdoor emissions; their tendency to spill smoke inside houses; and because they are wasteful of what we consider to be a valuable fuel.

Unfortunately, many, if not most, people have sentimental notions about the romance of an open fire. And since the banning of them is politically explosive and therefore unlikely in most jurisdictions, we promote education aimed at informing people about the downsides of choosing a 200 year old technology for their new homes.

Regarding VOC emissions, wood burners are fairly serious emitters, but tend not to be implicated in the production of ground level ozone because of the counter-seasonal pattern of use. That is, the intense sun and heat tend to occur in summer when VOC emissions from wood burning tend to be lowest. As a result, gas and diesel automotive exhaust is more strongly associated with smog than is wood burning. Also, smog and ozone are mostly generated in densely populated urban areas where wood burning is less frequent.

I would add one more piece of good news. Wood burning can be done with a fairly high energy return on energy invested, or, to state it more simply, high net energy. All energy that is made available for useful work requires energy inputs for extraction/harvesting, refining/processing and transportation to market. Because wood is only slightly processed from its natural form and because its use tends to be local, far less energy is consumed in making it available as a heating fuel than virtually all other options. In contrast, as the remaining oil and gas reserves get consumed, producers must go into more inhospitable places to get more, places like the Arctic and offshore under oceans.

They also have to tap into less appealing sources, like tar sands, in which huge energy investments must be made to get small returns. Then these fuels must be refined (at great efficiency losses) then piped half a continent away to market. Needless to say, wood wins hands-down in the net energy competition.

We strongly agree with your caution about toxics resulting from burning garbage. This is a serious problem that is only now attracting some attention.

One final point, we support the idea of regionally appropriate energy use. We certainly don't promote wood as a great fuel for all people everywhere, the way the conventional energy producers do. As I think we say somewhere on the site, wood is a good and appropriate fuel at the urban fringe and beyond and specifically in those regions where forested areas are plentiful. So, when wood is burned away from densely populated areas there are fewer people to breathe whatever emissions are produced. And while there continues to be some debate on the issue, it is our contention that wood smoke is a natural substance which is not inherently damaging to the environment, provided it is not breathed in high concentrations while it is airborne.

Installing an insert into your open fireplace is certainly the right thing to do. If it is installed correctly, you'll get around 70% net efficiency, a gorgeous fire, and a steep reduction in your conventional energy use. Given your knowledge of energy and environment, your choice and your explanation of it can be a powerful influence on those you come in contact with. Make sure you get that insert installed right.

Thanks again for your thoughtful note.

John Gulland