Can Weeds Hold the Key to Turning Farms Into Carbon-Storage Powerhouses?

Simon Kitol’s 25-acre farm in western Kenya teems with maize, tomatoes and beans, but also an invasive menace: Prosopis juliflora, better known as the mathenge plant. Its long roots steal water from his crops, and the shrub takes up valuable room for growing food. Kitol’s livestock also dine on the mathenge pods, which are loaded with sugar, causing even more problems.

“It damages their teeth, and eventually the cows or goats die,” Kitol says. The thickets also provide cover for predators like wild dogs and hyenas. “They hide there because it is so thick that you can’t see them. At night, when the goats or sheep walk around, they are attacked and killed.”

Last year, experts with Penn State’s PlantVillage project, which helps smallholder farmers adapt to climate change, arrived to train Kitol and others in the area on a clever way to turn mathenge from a problem into an asset. Workers gather up those troublesome weeds – biomass – and convert them into biochar, concentrated carbon that they “charge” with nutrients by mixing it with manure. Farmers then apply the mixture to their fields, sometimes planting grass that provides fodder for livestock. Kitol says that the biochar helps his soils retain water and improves their fertility, leading to higher yields.

Well beyond Kenya, biochar is having a moment: the worldwide market was worth $600 million last year and could rise to more than $3 billion next year. Anywhere people are producing waste biomass – corn stalks, weeds, dead trees – they’re also producing a powerful tool for sequestering carbon and improving soils. And if farmers can prove how much biomass they’re turning into biochar, they can prove how much carbon they’re putting back into the ground. Through a group like PlantVillage, a company can then pay those farmers to offset its carbon emissions. (Biochar in general accounts for more than 90% of durable carbon credits that have already been delivered worldwide.)