High Heat: Re:char Recharges African Soil

A start-up called re:char has a new take on an ancient idea that’s designed to enhance crop yields in the developing world by making  biochar accessible and affordable.

Biochar is made by a process known as pyrolysis, which heats organic matter such as waste farm produce, without oxygen. Instead of releasing carbon dioxide into the air as the matter burns, the carbon is locked away in solid charcoal-like chunks.

In addition to increasing crop yields, subsistence farmers can supplement their income while trapping atmospheric carbon and enriching depleted soils. Biochar can also be used as cooking fuel instead of cutting down trees for firewood.

“It’s a really ancient concept,” says re:char‘s founder and CEO Jason Aramburu. In a recent FastCompany interview, he explained: “In the Amazon basin for over 3,000 years indigenous farmers have been making charcoal and burying it in the ground. They did this because it improved the soil's ability to capture and retain nutrients, which led to increased crop yields. The soil is so fertile, that they call these sites terra preta, which means black earth in Portuguese. What the farmers didn't know 3,000 years ago was that biochar was actually making a lasting impact on the soil. Today at the sites where they buried the biochar, it's still in the ground. As a result of how fertile the land is, that biochar-rich land is worth about five times as much as the land without it.”

In Kenya re:char produces and sells a device called a rutuba kiln. "Rutuba" means soil fertility in Kiswahili. “The kiln costs us $25-30 to produce and we sell it to a farmer for less than the cost of two bags of fertilizer,” Aramburu says. “Most farmers in a year purchase 2-3 bags of fertilizer and that's typically the largest single purchase that they make.”

The kilns are made from repurposed oil barrels, made in a “mobile factory,” actually a 20-foot cargo shipping container outfitted with advanced metal fabrication tools. Re:char brings the factory to the farmer.

Aramburu says it’s a tricky sell. In Kenya a “lot of these farmers have seen lots of Western ideas come and go.” But re:char has hooked up with an NGO in the region, which has helped sell the concept. The company has also developed test sites in the area that demonstrate how biochar works, and re:char is also setting up a test farm with several different test plots.

This is an idea that could and should catch fire, so to speak. Recently re:char received a Gates Foundation grant to test the conversion of human waste into biochar. And last year re:char received the 2011 Social Venture Network Innovation Award.

Biochar is a great fertilizer, at least part of the answer for carbon sequestration, and a renewable fuel. While there is no single answer in renewable and sustainable fuel, it is the only energy source that’s “carbon negative.” It's also neat that old oil barrels are used as the kilns -- there are plenty of those around.

[Image credit: Rutuba kiln via re:char]