Using Biochar To Increase Food Production
by David A. Nuttle
For several hundred years, a few Amazonian Indian tribes have used a slash-and-char technique in the process of clearing forests to make fields to produce food crops. The timber biomass, removed from land, was placed in pits and started on fire, and then covered with enough soil to create a primitive charcoal kiln. A product called biochar was the result. This biochar was crushed and incorporated into the soils where crops were to be grown. The croplands so treated have long remained very productive, and are known as having so-called Terra preta soils (soils with biochar).
Research by Johannes Lehmann, Ph.D., at Cornell University, has established that the addition of biochar to soils reduces soil acidity, helps improve availability of water for plants, and increases soil microbial activity thereby providing natural fertility (thus, reducing the need for most fertilizers). At the same time, the biochar performs a carbon sequestration function benefiting the environment and reducing global warming. Biochar research will continue, at Cornell and other locations, to determine best practices when adding biochar to gardens/cropland. (Best Energies, Inc. is developing one of the first efficient slow pyrolysis systems for commercial biochar production.)
In New South Wales, Australia, Lukas Van Zwieten, Ph.D., and the New South Wales Dept. of Primary Industries, produced biochar using a slow pyrolysis technique to char biomass. Then 10 Mg/ha of biochar was tested on wheat fields, and the result was a 300 percent increase in wheat yields. Dr. Zwieten discovered that if pyrolysis occurs too rapidly the biochar has a bio-oil residue that may act to make soils toxic. In addition, it seems that biochar does not increase crop production on all types of soils. Ferrosol soils were used for Dr. Zwieten’s research. More work is needed to determine what soils should, and should not, be treated with biochar free of bio-oils.
Use of gasifiers requires limited oxygen/combustion, to convert biomass into 20 percent biochar, 20 percent syngas, and 60 percent bio-oil that may be refined for use as biodiesel fuel. More research is needed to determine if biochar produced by gasification will have the same crop fertility benefits as biochar produced by slow pyrolysis (without oxygen). By using slow pyrolysis, biochar yield is 30 to 50 percent, but there is no recovery of syngas or bio-oil. The immediate problem is that gasification is an expensive process, so the economic feasibility of using gasifiers (to make biochar) has yet to be determined.
In the U.S. alone, some 1.4 billion tons of old poultry litter would be available, each year, to make biochar soil treatments. At present, the U.S. has over one million acres of timber downed by Hurricane Katrina. This down timber could be used to soon produce large quantities of biochar rather than just letting old timber rot ---- and thereby produce more CO2 harmful to our environment. Obviously, we do have large quantities of biomass that could be used to make biochar. The Federated States of Micronesia are promoting the use of biochar to increase crop yields. At its next meeting, the U.N. Framework Convention on Climate Change will consider use of biochar as a means to provide more effective carbon sequestration. There is an International Biochar Initiative, under the direction of Debbie Reed. Thus, it seems that biochar is here to stay as a very effective way to increase food production.