Scientists, borrowing from the ancient Amazonians, have come up with a way to end smallholders’ dependency on fertilizers forever, by converting waste into charcoal that doubles yields and holds carbon and minerals in soils for centuries. The newfound cheaper fertilizer option has also been hailed by local scientists as friendly to the environment since it is made of materials that are absorbed fast by the crops and friendly to the soil.
Saw dust, crop residues and chicken manure are among the waste products being used in the Biochar project in Suba district of Western Kenya, with over 300 farmers reporting a doubling in yields as a result.
Biochar is a fine grained charcoal high in organic carbon and resistant to decomposition. To produce it, biomass like chicken manure and crop residue is heated in a closed container with little or no air, resulting in charcoal.
The smoke that comes out as a by-product is trapped and converted into fuel, while the charcoal is ground into powdered form and mixed with the soil. The burning without oxygen produces a stable carbon structure that take hundreds of years to biodegrade.
Scientists have discovered that adding charcoal or other charred materials to soil is a much more effective fertilizer than any methods currently in use. Land is naturally carbon-rich, but over time and with increased agricultural use and retillage, the carbon-rich materials break down into carbon dioxide and are released into the atmosphere.
Most fertilizers available today, even composts, break down quickly and are therefore only short-term solutions to soil depletion.
However, using charcoal in the soil adds a component that easily absorbs water, holds nutrients for hundreds of years, and provides rich minerals to plants. According to Erick Kingo, a scientist from the University of Nairobi involved in the Suba Biochar project, Biochar is a simple and powerful tool to fight global warming.
The burning and natural decomposition of trees and agricultural matter contributes a large amount of carbon released to the atmosphere. Biochar on the other hand stores carbon in the soil, potentially making for a significant reduction in atmospheric carbon dioxide levels.
“Biochar will increase the fertility of problem-soils in a very noticeable, quick and long-term way. This is important for subsistence farmers, because they often cannot afford to buy fertilizers or invest in organic cultivation techniques that take a long time to establish. Biochar can be produced locally, with very low investment, and in a simple, easily understood process," said Kingo.
He further argues that Biochar has slowed down the local deforestation rate by at least 50 per cent, boosted crop yields by 100 per cent, thus improving farm incomes and alleviating poverty and hunger, and reduced fire-wood consumption by households by 50 per cent, thanks to the introduction of char-producing cooking stoves “that burn very cleanly and efficiently”.
The majority of the subsistence farmers in Suba district seeking better soil have traditionally relied on slash-and-burn agriculture, which generates greenhouse gases and decimates forests. Now that farmers are slow-smoldering their agricultural waste to produce charcoal — in effect, slash-and-char agriculture — they can fertilize existing plots instead of clearing more land. This is reducing emissions in the atmosphere, and creating a virtuous circle of environmental renewal.
Typical of the new farmers is Joshua Okaro, who has a farm in Gwassi Hills that borders Suba District, where he is raising chickens for their manure, as well as their meat. "It might look like this is just a poultry farm," says Frye. "But it's a char farm too, which has made all the difference in my farm and saving me the heavy cost of fertilizers that were choking my budget."
The making of green charcoal for fuel gained international recognition in 2002, with the development of the 'Pyro' kiln. Pioneered by a Paris-based NGO, Pro-Natura, the charcoal-making machine has been used in Senegal since late 2007, producing fuel briquettes from flakes of green charcoal mixed with a binding agent such as starch, molasses or clay.
Unlike an ordinary kiln, organic matter can be continuously fed into the French-made Pyro, and charcoal extracted, with no need for repeated cooling and reheating. Its design means it requires little external fuelling, and can produce up to five tons of charcoal a day.
Gases released by the heating process are burned in a second, post-combustion chamber, maintaining the temperature of the oxygen-free kiln at 550°C. Excess gas may also be put to other uses, such as drying the organic feedstock, or heating greenhouses.Could it really be that simple? It appears to have been for the original inhabitants of the Amazon basin. In the 16th century, Spanish explorer Francisco de Orellana wrote home describing the remarkably fertile lands he had discovered there.
In the 19th century, American and Canadian geologists uncovered the reason: bands of terra preta (dark earth), which locals continued to cultivate successfully. Research revealed that the original inhabitants of the region had added charred wood and leaves — biochar — to their lands.
Centuries later, it was still there, enriching the soil. "You couldn't help but notice it. There would be all this poor, grayish soil, and then, right next to it, a tract of black that was several meters deep," says Johannes Lehmann, a soil scientist from Brazil who, inspired by this discovery, introduced the field trials in Western Kenya.
Currently, the process of using biochar in farming is being practiced only on a small scale, but scientists now argue that it could offer a breakthrough in mitigating climate change.