Concentration of CO2 in the Atmosphere

Burning Wood to Save the Forest

Once it is rotting, wood will not make good firewood. Decomposition driven by mushrooms might produce as much CO2 as a fire would. Photo: Nipunm, CC-BY-SA 4.0, Wikimedia Commons,

George Harvey

Generally speaking, I favor letting nature govern itself. There are times, however, when this simple approach really needs to be examined and modified. With increasingly extreme weather and the invasive species driven by climate change, there are times when human intervention may be necessary.

One such time is when fallen wood lies on the land. In one way or another, wood will become other substances when it is left to nature, and the question of which substances it becomes is especially important.

There are several ways wood decomposes in nature. Among the most important decomposing agents are fungi and insects. Another important way for wood to decompose is by burning, whether in natural fires or man-made ones. Each of these produces different results.

When fungi decompose wood, it is digested aerobically. Most of the carbon given off is carbon dioxide (CO₂), a greenhouse gas that causes global warming. In an entirely natural system, the CO₂ will eventually be absorbed by plants which convert it into chemicals they need for life.

Insects, such as termites, eat wood and use bacteria in their digestive systems to break it down anaerobically. This produces methane (CH₄), a much more powerful greenhouse gas than CO₂. Sometimes CH₄ is said to be over 80 times more powerful when considered over a short term such as 20 years. But over the long term, such as 100 years, CH₄ is said to be 20 times as powerful because it decomposes on its own in the atmosphere.

When wood burns naturally, the result can be a terrible mess. CO₂ may be the most important product of combustion, but there are lots of other products, including all sorts of particles that rise in the smoke, only to settle down at some distance as ground-level pollution.

The wildfires in the West this year have been horrible. The destruction of plants and animals has been extremely sad. And many people have seen their homes burn or their jobs lost. More have had to evacuate and live away from home, which is all the worse because of the Covid-19 pandemic. And even where the fires are hundreds of miles away, their pollution makes people sick. To some extent, forest falls contributed to this problem.

When we intentionally burn wood, the results can be very different. Years ago, an exceptionally fine scientist told me something that didn’t make sense at the time. He said, “You should have a Franklin stove. They make the air cleaner.” Decades later, I realized he said this because it is possible to burn wood while producing almost no emissions beyond CO₂. At the time, Franklin stoves and kitchen ranges were good bets for that.

Now, there are a lot of ways to burn wood cleanly in the home or commercially. Modern stoves and furnaces engineered for clean burning can be even cleaner, coming close to having only CO₂ and water as products of combustion that are released. In terms of emissions, they are much better than the cleanest stoves that existed when I was young.

One of the best things we can do with forests is to keep them clean by removing dying and dead trees and using them in well-engineered equipment. That way we can avoid methane emissions that insects give off, and we can reduce the probability of wildfires. But if you are going to harvest wood, remember to be safe. And use an electric chain saw with natural bar oil.

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