Wednesday, October 2, 2013

Carbon Sequestration

Carbon sequestration is taking carbon out of the atmosphere and sequestering it in the soil or plant material growing in the soil. The more organic matter in the soil, the more carbon you have locked up in the matrix.

In this post we will look at the science of soil building and sequestering carbon.

There are some more stable forms of organic matter that last a long, long time. Such as lignins, the organic matter remaining after woody plants break down.

Charcoal is the carbon matrix that remains after the water and terpines are remove at high heat in the absence of oxygen.

I was exploring the best ways to sequester carbon and stumbled upon some ideas from the ancient peoples of Central America. The Incas would improve their soils by adding biochar (charcoal) to their compost piles and then incorporate this into the soil where they grew their crops. This enrichment was so good that now hundreds or even thousands of years later these soils are mined and sold as a soil amendment or fertilizer in garden centers.

Reed and I were playing around with making charcoal from wood on the farm. We used several steel trash cans to limit oxygen and heated the "reactor vessel" using junk wood from the farm. We sold the big chunks at the farmers market for sustainable BBQs. But there are a lot of small pieces and dust that we incorporated into the soil. This form of carbon is very biologically active, similar to clay particles when it comes to exchanging nutrients with the plants. So when you first apply the biochar it may take some time to load up on nutrients. This can be accelerate by mixing the biochar with compost or other biologically active materials to speed things up.

With this approach it is possible to lock up carbon for 100's of years and enrich the soil. Interesting how those two things go together. When you look for one solution it is highly probably you can find other solutions as well.

I haven't gotten back to the charcoal making recently, but the beds where I used the charcoal are doing well.

More on this later.

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