Charcoal, Agriculture and Climate Change

Richard Haard is propagation manager at Fourth Corner Nurseries, a native plant nursery in Whatcom County.

This article was first published in the Fourth Corner Nurseries catalog, Spring 2008: http://www.fourthcornernurseries.com/Article16.asp.

Here is a global issue — our atmospheric carbon cloud. An emerging method for mitigating carbon emissions by burying charcoal needs advocates in order bring sequestration into play along with reductions of carbon emissions. It will take work on all fronts to reduce the carbon in our atmosphere, including this rediscovery of Amerindian agriculture — Terra Preta.

Let us first consider the difficulty of conducting farming in the humid tropics of Asia, Africa and South America. In this environment it is very difficult to maintain productive fertility of a farming tract for any length of time because the organic matter decomposes rapidly. These soils are naturally low in calcium and potassium while phosphorus is tied up in a complex with aluminum, mostly unavailable to plants.

Without continuously adding manure, compost or chemical supplements this soil becomes nonproductive in two to three years and must revert to forest for 10 to 20 years before farming can be supported again. Even after this nutritional support, 10 years would be a maximum time crops could be grown before an extended fallow period would be needed.

After recovery of the land, the farmer then slashes and burns the accumulated vegetation and repeats this cycle. Hence the term “slash and burn” (Swidden) agriculture. Now prominent scientists are advocating replacing this with a new kind of agriculture — “slash and char.” This growing system also has advantages in the temperate zone.

Slash and burn agriculture is practiced by 300 to 500 million people on one third of the 1,500 million hectares of arable land on the planet. Yet pressures remain high for clearing of natural habitat in order to expand agriculture. This is because of the expanding population, countries’ needs for export market income and American and EU demand for biomass fuels.

In Brazil alone carbon emissions from annual forest clearing amounts to 20 percent of the total carbon released in the country.

There is another type of tropical agriculture called slash and char, which promotes soil fertility, allows for shorter rotation periods and also reduces dependence on chemical fertilizers. This farming technique was formerly practiced by the Amerindian people 500 to 2,500 years ago and was discovered independently in Asia.

It is quite a simple concept, actually. These native Amazon rainforest farmers had only stone tools, and felling the forest for fresh, fertile ground was very difficult. Instead, they conducted a smothered combustion of agricultural debris, and supplemented this with domestic manure and household debris.

This charcoal built up in the soil over time and became a durable substitute for soil organic matter. This black carbon lasts for tens of thousands of years in the soil. The result is a soil with chemical and biological properties that convert unproductive tropical soils (oxisols) to fertile soils that are still farmed even 1,000 years after the original people have disappeared.

Here then we have a way to take pressure from land clearing in the tropics, to make more food for people and, most interesting of all, to mitigate atmospheric carbon pollution by burying charcoal. Large-scale adoption of slash and char, conversion of agricultural and forest waste to biochar, and biofuel production with charcoal as an end product could cumulatively result in carbon sequestration greater than current emissions from fossil fuels.

Indeed, this system of burying charcoal is superior to tree plantations and standing crop biomass. The latter system is transient. And tree plantation forests can become carbon emitters when the trees mature (climax succession stage).

Fourth Corner Nurseries, a native plant nursery in Whatcom County where I’m the propagation manager, is conducting research into charcoal as a soil additive. Since 2003 we have been testing this material, and a progress report on this research project is now posted at http://terrapreta.bioenergylists.org. You can find postings with a key word search at http://terrapreta.bioenergylists.org/search/node/haard+charcoal.

We are encouraged by our early results from our block treatment study, a project that will continue for several more years. From our local fieldwork and also from reports of other hands-on workers around the globe, charcoal is an excellent material to use as a soil additive.

Burying charcoal improves the water-holding capacity, soil pH, cation exchange capacity, base exchange and, most important of all, makes new habitat for beneficial microorganisms. The increase in surface area made available by charcoal is amazing. A single gram of charcoal powder can have a surface area of 1,500 square meters. Far from being inert, charcoal is a highly valuable component, providing active retention of nutrients as well as increased micro-life and stabilization of the chemical environment.

Do not put fresh charcoal into the soil! If you put fresh charcoal into soil, the fertility might actually decrease. In addition, we have noticed charcoal has a water-repelling property that needs to be biodegraded before waterborne nutrients can be transmitted into the internal structure of what was once the vascular system of the plant.

In the conditioning process, the large inner surface of charcoal causes nutrients to adhere, making them temporarily unavailable to plants and microbes until the charcoal is saturated with water. Once saturated the charcoal becomes attractive to plant roots and soil microbes. Because of the inorganic nature of this substrate, the charcoal serves as an enrichment culture for nitrogen-fixing and mycorrhizial organisms.

Think about composting with manure, urine, wood chips and /or nitrogen fixed by legume crops before or after use. We have been working on this approach, as have others. Our local group has found that after several months in these aerobic conditions, the charcoal is water-saturated and completely involved with fungi and macroscopic invertebrates. Our best results thus far are with charcoal treated in this way.

If you are thinking about making agricultural charcoal you should know there are additional components of this conversion that benefit plants: smoke (pyroligneous acid) and burned soil. See Christoph Steiner’s dissertation, pages 35 to 42. This is the chapter on current indigenous gardening methods. Terra Queimada, burned soil, and Terra Cheirosa, smelling soil (pyroligneous acid), as well as the volatile materials that accompany fresh charcoal stimulate microbial activity.

TPp or Terra Preta (prehistoric) is a human-made soil type dated 500 to 2,500 years old and has a different respiration response profile than the newly created TPn or Terra Preta Nova. You cannot expect to make TP overnight. It will always be a work in progress.

If you are a municipality, think about making biochar rather than composting shredded tree/garden waste or household debris and sewage/dairy solids. This is environmentally possible on a mini or meso scale and will pay for itself.

If you are a farmer you could char your waste rather than burn. In addition, woody cover crops like willows and alder can be a feedstock for a small pyrolyser, which can supply process heat and charcoal for your field. Our pit char system burned quite clean, yielded a high grade of low-temperature charcoal and was a lot of fun to do at least once.

If you’re interested in using/experimenting with charcoal in your garden or are interested in simply discussing and learning about this idea with local people, please join the discussion list we have formed, maintained by Larry Williams, lwilliams@nas.com.

At some point this summer I would like to host with Larry a gathering of gardeners and conduct a field trip to view our trials with charcoal. We have a discussion list managed by Tom Miles in Portland you can join (see http://bioenergylists.org/mailman/listinfo/terrapreta_bioenergylists.org.)

By reading the archives and the current postings you will learn what gardeners, small farmers and even scientists are discussing in this very active global Internet forum.

Sometimes we see great results. Where soils are poor and prone to nutrient leakage (like tropical soils), differences will be striking. When organic matter and soil fertility are already high, results will be muted. However, overall there will be an improvement in plant growth, ease of fertility management and general health of the soils.

We’ll be learning more about this system of agriculture as research hits the mainstream. There is potential income to farmers for carbon credits. Will there be patents and trade secrets? Hell, no. This is an open source intergenerational gift from our original peoples of South America and we owe a debt to them to use this traditional knowledge to protect the earth. §

Slash and Char as Mitigation for Climate Change

• Lehmann J, Gaunt J, Rondon M, (2006) Bio-char sequestration in terrestrial ecosystems – A Review. In Mitigation and Adaptation Strategies for Global Change 11, 403-427.

• Lehmann, Johannes, “A handful of carbon,” Nature 447, 143-144, 2007.

Basic Knowledge and Science

• Web access for Dr. Lehmann’s work: http://www.css.cornell.edu/faculty/lehmann/biochar/Biochar_home.htm.

• Steiner, Christoph (2006) “Slash and Char as Alternative to Slash and Burn,” Dissertation, University of Bayreuth, Germany, 185 pp., Cuvillier Verlag Gottingen.

• Lehmann, J., D.C., Kern, B. Glaser and W. I. Woods (eds), 2003: “Amazonian Dark Earths: Origin, Properties, Management,” Kluwer Academic Publishers. Netherlands.

• Ogawa, M. (1994) “Symbiosis of people and nature in the tropics.” Farming Japan 28(5): 10–30.

• T. H. DeLuca; M. D. MacKenzie; M. J. Gundale; W. E. Holben, “Wildfire-Produced Charcoal Directly Influences Nitrogen Cycling in Ponderosa Pine Forests,” Soil Science Society of America Journal, Volume 70, Number 70, p. 448-453 (2006).

• Gunther, Folke. We have been given access to an excellent educational PowerPoint program: “Carbon Dioxide, Deciding for Our Future,” Holon Ecosystems Consultants, Lund, Sweden. You can find it at: http://www. terrapreta.bioenergy lists.org.

• Haard, Richard. Richard’s Flickr collection of charcoal and agriculture images and latest report on charcoal research at: http://www.flickr.com/photos/rchaard/collections/72157600824315154.

An Excellent Web Resource and Reading List:

http://terrapreta.bioenergylists.org/about.

An Upcoming International Conference:

Newcastle, UK , September 8, 2008 — http://www.biochar-international.org/ibi2008conference.html.

Source Material for This Article Included:

Folke Günther, Holon Ecosystem Consultants, Lund, Sweden, “Carbon sequestration for everybody: decrease atmospheric carbon dioxide, earn money and improve the soil,” submitted to Energy and Environment, 3/27/2007. This article can be downloaded at: http://www.terrapreta.bioenergylists.org.