“Terra preta” or “black soil” is very fertile, dark and manmade soil found in the Amazon. It’s the result of an indigenous farmers’ practice 3000 years ago, they would bury charcoal in the ground to boost the otherwise relatively infertile Amazonian soil. The charcoal allows the soil to capture and retain nutrients better, leading to higher crop yields. Back then the farmers didn’t know their practices would have a lasting impact on the land. Yet today, the terra preta sites are worth five times more than sites with regular soil.

Inspired by this ancient technique Jason Aramburu founded Re:char. Re:char sells kilns to African farmers that allow them to create “biochar” from their agricultural waste. Biochar is a charcoal that can be used both for cooking and as a soil amendment. Now you might think that this is just another attempt at carbon neutral sustainable energy, and it is. But it’s not just that, biochar is actually carbon-negative.

Negative?

Yes.

Fossil fuels, we all know, are carbon positive meaning that they add more CO₂ to the air thus contributing to global warming. Renewable energy sources are carbon neutral at best. Biomass fuels capture the carbon that would have eventually returned to the atmosphere through natural processes and even solar power doesn’t have the ability to extract CO₂ from the air. But this is what biochar does. By transforming the carbon in biomass into stable carbon structures, it can remain stored in the soil for thousands of year, resulting in a net reduction of CO₂ while simultaneously enriching the soil for increased crop yields.

Currently, small-scale farmers in Kenya spend nearly half their yearly income on fertilizers that are less effective and a lot less sustainable than biochar. So using biochar does not only make sense in terms of sustainability, it’s actually quite a significant cost saver.

Re:char is currently focusing on small scale sugar cane and maize farmers in Kenya, a difficult group to target since they’ve seen a lot of “product pushing” from the Western world. Luckily, it takes the farmers on average just 6 months to reap the benefits of using biochar, which is a lot quicker than other sustainable energy sources. Moreover, buying a kiln costs less than 2 bags of fertilizers (the targeted farmers will buy 2-3 bags of fertilizers a year) so there is no big investment in technology needed.

In “mobile factories” Re:char is making the kilns from old oil barrels. They’ve outfitted a regular 20-foot container with all the appropriate tools and use this as a mobile factory, allowing them to reach even the most rural areas in Africa and produce kilns locally.