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Biochar for Self-Reliant Garden and Farm Abundance

Written by Dan Brunet on 26 August 2010.

Biochar expert Josiah Hunt presents at Imin Center.
Biochar expert Josiah Hunt presents at Imin Center.
Okay, now I am excited. Why? In a word, "biochar." In his introduction to this July 25, 2010 workshop, Craig Elevitch said that biochar will permanently change the way we do agriculture. Yes, it could very well help save ourselves from industrial, high-input agriculture, helping to rapidly repair the soil damage our species has caused while sequestering carbon for a very long time. Organic matter that might otherwise contribute to mounting landfills can also be diverted to the biochar process.

The workshop presenter was Josiah Hunt, a man on a mission to share biochar with the world. Biochar is obtained by heating organic matter (usually woody material) to a temperature about 500-600 degrees Celsius (about 1000 degrees Fahrenheit), burning off all the volatile substances, then depriving the remaining carbon of oxygen and cooling it. What remains is a crumbly, brittle carbon matrix left in the structure of the wood that was charred. Biochar can hold many times its weight in water, provides a huge surface area for microorganisms, and adsorbs (holds on to) nutrients that would otherwise leach out of the soil. All of this is very good for soil health!

Hunt presented results from research as well as hands-on experience.
Hunt presented results from research as well as hands-on experience.
You may be wondering about the difference between biochar and regular charcoal that you can buy for your barbeque. Charcoal is heated to about 300-400 degrees Celsius (roughly 700 degrees F.), then cooled. Usually, much of the volatile substances remain, which can be toxic to soil organisms. Also charcoal tends to repel water, rather than sponge it up, and doesn't have the extremely open matrix structure of biochar. In short, most charcoal you can buy can be harmful or of little benefit to soil.

Researchers such as Hunt have found that biochar incorporated into soil can increase yields year by year. For example, in one study, yields increased 28% the first year, 38% the second year, 75% the third year, and 150% the fourth year. It appears that biochar has an enhanced effect as it ages in soil. Results vary by soil type and condition—in general, the most effect is seen on poor soils and the least effect in rich soils.

Hunt demonstrated techniques for incorporating biochar into a garden bed at Holuakoa Cafe in Holualoa.
Hunt demonstrated techniques for incorporating biochar into a garden bed at Holuakoa Cafe in Holualoa.
One stunning  research finding is that biochar can last for thousands of years in the soil. That means once it's applied, it will provide benefits for generations. If you think of biochar as money invested, biochar pays dividends every year in higher yields and savings in terms of nutrients that would otherwise be leached away. The rich soils of the Amazon called Terra Preta ("black earth") contain large amounts of biochar. These soils, some almost 8 ft thick, are still much more fertile than the surrounding native soils, even hundreds of years after human populations disappeared. Terra Preta lands are thought to have supported populations of millions of people (as reported by early explorers). Compare this with today's massive clearing of the Amazon rainforest for industrial cropping that can only be sustained for a few years due to the poor soil.

Where can you get biochar? It is available commercially from Hunt, who sells all the biochar he can make by cubic foot, cubic yard, or ton. You can also buy Hunt's biochar in soil mixtures and vermicompost made by other companies. You can also make biochar yourself using various low-tech methods, one of which is similar to a Hawaiian imu. Making biochar is something of an art form, so learning from an expert such as Hunt is recommended.

Take heart Gaia. We are remembering how to take care of you through the use of humble, simple means such as biochar.

For more information visit Josiah Hunt's web site at landscapeecology-hawaii.com