Thousands of years ago, the Indigenous peoples of the Amazon accidentally invented a powerful climate solution.
Perhaps surprisingly, the soils of the rainforest are nutrient-poor, so farmers needed to create an enhanced soil. They called it “terra preta” (black soil) and boosted the soil by adding discarded food scraps and charcoal. Today, that ancient technique is being used to create something similar called biochar - it simultaneously improves crop yields, retains water by soaking up rain, and stores lots and lots of carbon.
Previous estimates reckoned that after 100 years, between 63 percent and 82 percent of that biochar (and the carbon it holds) will remain in the soil. But a new paper argues that 90 percent of the biochar will still be in the soil after thousands of years, making it an even more powerful climate solution than first thought.
The evidence for this comes from a material in Earth’s crust called inertinite, which formed when ancient forests caught on fire and fossilized. Biochar essentially replicates that process, so it should also last for a long while, they argue - surviving biochar in ancient terra preta is evidence.
Biochar is a negative emissions technology that’s already proven on a large scale. This revolution started in Stockholm, where, after opening its first five biochar plants in 2017, the city began distributing this new fertilizer/soil amendment to citizens for free, if they merely bring whatever yard waste they might have. In 2022, Bloomberg Philanthropies awarded grants of $400,000 to four major cities in Europe and three in the U.S. to implement the biochar technology.
Last year, a study found that crop residue biochar could lock up 7 percent of global emissions, stating that crop residues that lie scattered across thousands of farmlands globally could be a brilliant secret weapon against climate change.
It's worth noting that direct air capture machines that suck carbon out of the atmosphere remain expensive and limited in scope. “Biochar is already a compelling solution,” said Thomas A. Trabold, a sustainability scientist at the Rochester Institute of Technology and CEO of Cinterest, a company developing biochar technology. “This data just suggests that the benefits are even greater than we already assumed.”