Biochar for Carbon Sequestration

Over the last few weeks there has been talk in the media on the need to increase the carbon content in our soil. The motivation mentioned is to reduce our liability under Kyoto. The reason we are not doing so is said to be the difficulty in measuring increases in Carbon.

Kyoto is all about the extent of change from the present situation and not about the  amount of carbon a country is currently sequestering.

A carbon rich soil, all else being equal, is a soil with more humus and other organic content such as the microfauna and miafauna. In other words a healthier more productive soil. I think there is a way of solving both the problem of increasing carbon and of having a reliable measurement which could be used to calculate our level of carbon sequestration and hence calculating our reduced liability under Kyoto.

How about if we incorporate charcoal into the soil. At first glance you might think that this is a scam. What good would it do to put charcoal into the soil. It is hardly worth doing it just to be able to say that the carbon content has increased. Have a look at this site for an explanation of the technical side of charcoal in soil.  Apparently charcoal fills at least some of the functions of Humus and is refractory at temperatures at which humus breaks down.



If charcoal is as refractory to breaking down as I have been led to believe, the amount we apply is the amount we can claim credited for.

What is needed first is a small research project in which charcoal is incorporated into soil. A random bunch of questions to be answered include:

1. Does charcoal actually hold nutrients and release them to the plants. In other words does it perform the function of humus. Recent work on Terra Preta suggests that it does.

2. Does the charcoal persist in the soil (probably) and if so, for how long.

3. If it does persist, does it's nutrient holding ability remain.

4. What is the effect of charcoal on the water retaining properties of soil

5. What is the effect of charcoal on the structure of the soil.

6. What is the effect of charcoal on the flora and fauna of the soil.

7. What is the effect of charcoal on the growth of plants which are rooted in the soil with respect to the amount of fertilizer needed, the persistence of nutrients in the soil and the leaching of nutrients out of the soil.

8. What is the effect on all of the above with respect to the particle size of the charcoal used.

There are many more questions that any agricultural scientist will come up with.

I have been experimenting with the production of charcoal over the past year. It is technically simple to obtain the benefit from the heat from burning the volatiles which are driven off during charcoal production while at the same time ensuring that there is a large yield of charcoal. Some feed stocks which can be used include the branches from putting lifts on trees, all off cuts and sawdust from lumber mills, all offcuts and sawdust from house and furniture manufacture, and even waste paper and cardboard. One can even include bones from abattoirs, thus incorporating some calcium and phosphorus in the resulting product. Using the method in the above link, even paper and cardboard can be turned into biochar.

If biochar turns out to be a valuable soil conditioner, New Zealand could end up in credit with respect to our net production of Carbon dioxide while at the same time improving our soils.