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Ask the Conservationist

September 2010: Campfires and CO2

Did you go camping this summer? Campfires often spark more than just flickering light — they can lead to bright ideas and questions, like this one from a reader in Florida who wonders how the CO2 output of campfires compares to letting wood rot.

Find out the answer from Conservancy scientists, and when you're done reading, send us your questions on any conservation subject for one of the Conservancy's hundreds of staff scientists. (Note: We regret that we can only answer one or two questions each month and that we cannot answer the others offline.)

Ross P. Henderson of Tallahassee, Florida, writes:

My burning question: Is burning dead wood (e.g. campfire) much worse for CO2 production than letting it rot?

Mary Huffman, fire ecologist for the Conservancy's North America region, and David Ganz, forest carbon science director, reply:

Dear Ross,

Hmm. For an exact answer, we would need to do some calculations based on what kind of wood it is, in what ecosystem you are camping, how efficiently your fire is burning and several other factors. But the general answer is: no, burning dead wood in a campfire probably doesn't emit more CO2 compared with letting the wood decompose.

To answer your question properly, let's start with a little science lesson.

Consider how wood is made in the first place: the sun and photosynthesis snatch CO2 out of the air and use the sun's energy to split off the carbon atoms and string them together into wood fiber. That takes energy, which always has the potential to be released. As long as the tree is alive, the wood stays together and carbon is stored.

As soon as the tree dies, microorganisms begin digesting the wood to collect the energy stored there. They break the carbon-to-carbon bonds, use the energy to grow, and this process releases CO2 into the atmosphere as a by-product. The process can take years or even decades, depending on the decay rates in your particular ecosystem.

Funny thing, a campfire does essentially the same thing. Combustion, or burning, breaks those carbon-to-carbon bonds — only this time the energy is released as the lovely light of flames and soothing heat. The process is much faster, taking only as long as it takes to burn the wood.

So, whether you burn your wood completely or put it out and scatter the leftovers to rot, your choice says more about the rate of CO2 release than the amount.

If you're really hoping that you can still have campfires while reducing your carbon footprint, take solace in this small contribution. If you have partially burned logs leftover, that black layer of charcoal on the outside of the remaining wood contains between 50-95 percent carbon, in a form that will resist rotting (CO2 release). If you scatter this charcoal back onto the ground, it will eventually break into little pieces that stay stored in the soil, sometimes for thousands of years.

Of course, it would be a different story CO2-wise, if we were talking about burning live trees, say, in a wildfire. Although many ecosystems can withstand periodic fires — and may even require fire to persist — unplanned forest fires can generate extraordinary amounts of greenhouse gases. (This is in contrast to the controlled burns conducted by the Conservancy and others in fire-adapted forests and grasslands, which Mary discussed in the May 2010 "Ask the Conservationist" feature.)

So, when you are convening with Mother Nature, always keep watch over your fire, tend it carefully and extinguish it completely — and read our tips on how to avoid accidentally starting a fire.

Finally, don't forget another hazard of campfires: transporting firewood. Many campers unknowingly spread highly destructive invasive species — like the Asian longhorned beetle and emerald ash borer — by transporting firewood. So help keep these tree killers contained by obtaining your campfire wood locally.


 

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