The data are pretty clear,” explained Johannes Lehmann, a soil scientist at Cornell University and leading expert on biochar. “It is one of the most important technologies we have to draw carbon dioxide from the atmosphere.”
The technical potential—what’s achievable in optimal circumstances—is somewhere between 5 to 8 gigatons of carbon dioxide a year, Lehmann explained.
Overall, global emissions from fossil fuels were 37 gigatons in 2019.
Biochar is a high-grade form of charcoal that’s created when biomass—from plant material or manure—undergoes a process called pyrolysis, in which the biomass is heated in a low or no-oxygen environment. The result is a carbon-dense material that, when buried in the soil, can store carbon there indefinitely, and has added benefits, including enriching soil fertility and improving tolerance to drought.
Spent plant material and animal waste release carbon dioxide quickly. Biochar locks away the carbon in that material and waste, potentially for thousands of years.
“There’s not driving anymore and completely cutting off fuel use—that would be helpful,” Lehmann said. “But in terms of withdrawing CO2, there’s a limited amount of options, and biochar is one of those half-dozen options that can be deployed.”
The potential is huge, but like other land-based drawdown options, challenging for reasons that have little to do with science. The potential is on a similar scale, meaning each strategy represents a tool in a tool box, not a complete solution on its own.
Like planting new forests or soil carbon sequestration, the hurdles are economic, social and political. The challenge is finding the political will and economic incentives, Lehmann said.
“If we can decrease the barriers to entry with subsidies or other help, that’s what we should be doing,” Lehmann said. “Once biochar is in there, it’s hard to get out. I think it’s a no-regrets strategy.”