Sunday, October 25, 2015

Biochar: naturally increasing soil fertility, sequestering carbon

Increasing evidence suggests that biochar—the residue of burning plant matter in an oxygen-starved environment—can be extremely important in improving fertility of poor soils.

Hawai`i researchers have worked on ways of producing the material from macadamia husks and other local products, including sewage sludge. It comes out as shards, splinters, chunks and powder that some have called agriculture’s black gold.

More and more, that evidence is coming down on the side of char. University of Hawai`i researcher Michael Antal has a great deal of information at this website.

Biochar has been promoted as a valuable soil amendment for any farming system, including organic, backyard, third world, conventional and more. 

The US Department of Agriculture reports extensively on biochar, and says that studies with numerous crops showed significant increases in production with many of them. 

Field tests in the African nation of Burkina Faso have shown that soils treated with biochar produce heads of lettuce that weigh more than those grown in untreated soils, all other things being equal. The Urban FoodPlus project, outlined in the magazine Rubin, showed that not only was the soil better at growing crops, but the biochar locked up carbon in the soil, serving to counter CO2 buildup in the atmosphere.

Biochar may help with water retention and may also promote better nutrient uptake. It also sequesters carbon, reduces soil acidity.

A lot of the early work on biochar in soil is built on the discovery in the Amazon area of vast areas of dark soils called terra preta, in which early peoples have introduced charcoal into the soil, ostensibly to improve crop potential.

But there are caveats with this process. One of them involves the availability and loss of the plant materials that are burned to produce biochar. Some researchers are working on other feedstocks for biochar, including livestock manure and even sewage.

Spanish researchers at the University of Madrid used cattle, pig and chicken manure to produce biochar.

Another group used sewage sludge, and had good results. “The obtained results so far are quite encouraging as they show how the addition of biochar to soil can enhance its quality (for example, its ability for moisture retention, pH or biological activity) and therefore, to enhance crop yields,” wrote Science Daily on the work.  

The International Biochar Initiative celebrates the benefits of this material. On its website, the IBI crows about Brazilian soils into which the biochar was introduced hundreds of years ago: “These soils continue to ‘hold’ carbon today and remain so nutrient rich that they have been dug up and sold as potting soil in Brazilian markets.”

The IBI website has extensive information on how to go about the process.

For Hawai`i-specific information see and

© Jan TenBruggencate 2015

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