Burning Questions: Some Thoughts on Firewood and the Environment, Part 2

My head is feeling better so I’m back blogging on firewood, picking up where I left off on Part 1 of this theme.

Did anyone take a look at the Manomet Report? It concludes that using wood for heat (or for combined heat and electricity generation) is most likely to have a carbon benefit over the next 40 years, especially when compared to using it just to generate electricity. The report also states that this benefit would be about a 25 percent reduction in carbon emissions, again over a 40-year period, when compared to burning #6 heating oil for heat if the timber harvesting were done pretty moderately. (We generally burn #2 heating oil in Maine, which releases less CO2 per unit of energy than #6 oil, so in the case of burning firewood in a typical Maine house, the benefit might be less than 25 percent, and Manomet was not looking at residential heating specifically, so keep that in mind, too).  Manomet’s numbers on the carbon benefit of burning wood as compared to fossil fuels vary greatly depending on how the harvesting is done and how efficiently the wood is burned.

When a biomass plant in Maine uses wood to make electricity, for example, the wood is often “green” (wet), and that means burning it is less efficient. Also, biomass plants that just make electricity can only be about 20-25 percent efficient at best because of the laws of thermodynamics, whereas a good wood stove can be 60-80 percent efficient (mine is 72 percent efficient according to the manufacturer, but of course, you have to run your stove correctly for it to be efficient). So, using wood for heat certainly makes more sense than using it for electricity-generation at the typical biomass plant. In fact, Manomet concludes that burning wood for electricity at stand-alone biomass plants—the type we have in Maine—results in slightly greater carbon emissions than burning coal to make electricity and much greater carbon emissions than using natural gas over a 40-year period. We need to figure out other ways to generate electricity cleanly, and we need to conserve more and focus on efficiency. Big biomass electric plants are not the answer.

So, why do I burn wood to heat my house? My wood stove and cutting my own firewood are two of the things I do in Maine that make me the most happy. I guess that’s the biggest reason. Getting my own wood makes me feel a strong connection to the land around me, and though I know it is largely an illusion, it also gives me a greater sense of control over my own fate. I know many other people are equally attached to their woodstoves even if they don’t spend six months a year cutting firewood by hand. The best we can all do is to make sure we try to use our wood well. That makes it most likely that we will see some carbon benefit from heating with wood, as the Manomet report predicts.

Here are some things that can help with that:

• Insulate your house well. If your house is well insulated, you need less fuel of any type to keep warm and that reduces carbon dioxide emissions.
• Make sure your stove is as efficient as possible. If you have an old stove and can bear and afford to part with it, get an EPA-certified wood stove. They are much more efficient and emit less of the pollution that causes respiratory problems (I have asthma, so I appreciate people using cleaner burning stoves).
• Make sure your wood is as dry as possible. The drier it is the more efficiently it will burn. This is important! One way you can do this is to make sure your wood sits in a good, sunny spot (that’s how I do it).  Another way is to get your wood a year in advance so it gets two summers to try (this is for very organized people only).
• Make sure you run your stove at the temperature the manufacturer says makes it most efficient.
• Try to make sure your wood is coming from a source where the trees will likely be allowed regrow. Getting wood from well managed forests can only be good for the environment.

There are many other factors that will affect how burning wood impacts carbon emissions.  These are just a few, and there are other things to consider when burning wood than climate change. Wood spills are easier to clean up than oil spills (See, for example, http://www.nytimes.com/2010/06/17/world/africa/17nigeria.html for a horrifying description of oil spills in Nigeria).  Although particulate emissions are high from burning wood to heat homes and can aggravate asthma, sometimes severely, living near an oil refinery or oil flare can also aggravate asthma (for another example from Nigeria see: www.independent.co.uk/news/world/africa/visible-space-deadly-earth-gas-flares-nigeria-1955108.html).

Burning wood is not going to save us from climate change or end our addiction to oil. It can only be a small help at best, both because it emits a lot of CO2 and because wood is a very limited resource. David Pimental at Cornell University estimates that Americans use more than twice as much energy each year as every green plant in the U.S. can photosynthesize (Pimentel, David and Patzek, Tad. 2006. Green Plants, Fossil Fuels, and Now Biofuels BioScience 56(11): 875).  We cannot just substitute wood or other biofuels for fossil fuels and go on our merry way. We need to reduce the amount of carbon-containing material we burn as a society dramatically.

For me, I like using firewood to heat my home too much not to use it, and it reduces my use of heating oil by about 60%. I take the steps I can to make sure I use the wood efficiently.

(My wood pile. Or is it art? Or both!)

I get my wood close to home. And again, I don’t even use a chainsaw. That only makes a little difference in terms of reducing greenhouse gas emissions, but it greatly reduces smell and noise pollution.  I am also forced to cut down smaller trees and make greater use of tops and limbs than if I used a chain saw (this is because it takes a lot of work to fell a tree with an axe and hand saw, more work than cutting a tree up.  I can’t be picky and just take the nice big wood that splits easily and then move on to another tree). This may help reduce the carbon footprint, because there is less “carbon debt” associated with smaller trees. Tops and limbs may have a lower carbon profile than the stems (trunks) of trees because they are likely to rot faster (so says one theory, although it has not been rigorously tested). But, I don’t use all of the tops and limbs because it is important to leave a fair amount of them behind to replenish soil nutrients and provide habitat and food for all kinds of critters. Large pieces of wood are important to leave behind for similar reasons.

(My two dogs – Percy, in the top photo, and Atlas, second photo – appreciate that I use a hand saw rather than a chain saw, not because of the carbon emissions, but because it allows more restful naps!)

I guess, in addition to liking the workout and the quiet, I use a handsaw because trees work so hard for so long to get big enough to burn. It makes me feel better to have to work for a while to cut a tree down. I don’t kid myself into thinking burning wood is wonderful for the environment, but burning oil isn’t either, and I like burning wood. I believe wood-burning can be helpful for the environment in some ways and in some circumstances, and heating homes is likely to be one of the best ways to use wood fuel. I hope this blog makes it clear, though, that there are lots of caveats to this, and that it is important to use our wood as efficiently as possible. In a complex world, sometimes that’s as good as it gets.