Biochar study: surface soil carbon gains but deeper losses over 12 years

A 12 year field study published in the journal Biochar found that biochar increases stable carbon storage in topsoil but reduces carbon in deeper soil layers. The research tracked farmland over more than a decade and showed that while biochar locks carbon near the surface through boosted microbial activity, it causes a decline in carbon deeper down. This complicates the simple narrative that biochar is a straightforward carbon removal tool for agriculture. The findings matter for carbon credit projects that rely on biochar for soil carbon sequestration. If deeper soil layers lose carbon over time, net carbon accounting becomes more complex. Project developers and buyers should look closely at measurement depth and long term monitoring before assuming biochar delivers permanent carbon storage across the full soil profile.