ScienceDaily (Mar. 22, 2012) — Backyard gardeners who make their own charcoal soil additives, or biochar, should take care to heat their charcoal to at least 450 degrees Celsius to ensure that water and nutrients get to their plants, according to a new study by Rice University scientists.
The study, published this week in the Journal of Biomass and Bioenergy, is timely because biochar is attracting thousands of amateur and professional gardeners, and some companies are also scaling up industrial biochar production.
“When it’s done right, adding biochar to soil can improve hydrology and make more nutrients available to plants,” said Rice biogeochemist Caroline Masiello, the lead researcher on the new study.
The practice of adding biochar to topsoil to boost crop growth goes back centuries, but in recent years, international interest groups have begun touting biochar’s climate benefits as well. Biochar removes carbon from the atmosphere and locks it into the soil for hundreds and sometimes thousands of years.
With companies scaling up production and dozens of do-it-yourself videos online showing how to make biochar at home, Masiello said it is important for scientists to study examine how biochar is produced and learn which methods produce the best biochar.
In their study, Masiello’s team learned that when it comes to helping get water to plants, not all forms of biochar are the same. The researchers found charcoal produced at temperatures of 450 Celsius or higher was most likely to improve soil drainage and make more water available to plants, while charcoal produced at lower temperatures could sometimes repel water.
Rice’s award-winning biochar research group examined the hydrologic properties of biochar produced at various temperatures from three kinds of feedstock — tree leaves, corn stalks and wood chips. For all feedstocks, the researchers found that biochar produced at temperatures above 450 degrees Celsius (842 degrees Fahrenheit) had optimal properties for improving soil drainage and storing carbon.
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