For hundreds of years, farmers in Brazil’s Amazon Basin have hunted through dense jungles for what is called “terra preta” — mysterious plots of super-fertile black soil amid otherwise nutrient-stripped earth.

In recent decades, researchers have discovered that the rich properties of terra preta stem from the carbon-heavy leftovers of ancient cooking sites. Now, University of Florida researchers have found we can make our own version of the soil’s potent component, a form of charcoal dubbed biochar, from the remnants of renewable fuel production.

“This could possibly improve the viability of certain biofuels by giving a valuable — both economically and environmentally — byproduct from material that would otherwise just be a disposal problem,” said Bin Gao, an assistant professor of agricultural and biological engineering at UF’s Institute of Food and Agricultural Sciences.

For example, a renewable form of natural gas can be produced by “digesting” organic material with the help of added bacteria.