There are a half-dozen TED talks on biochar, many from familiar faces:
Biochar: The Oldest New Thing You've Never Heard Of: Wae Nelson at TEDxOrlando: https://www.youtube.com/watch?v=NrDOLx57KUU
Biochar -- Putting the carbon Genie back in the bottle: Rob Lerner at TEDxSanMiguelDeAllende (2013): https://www.youtube.com/watch?v=SgwwV6YrWb0
TEDxHilo - Josiah Hunt - Biochar and the Future of Farming: https://www.youtube.com/watch?v=SWbomZJn83U
TEDxBerkeley - Lopa Brunjes - Biochar: An Ancient Solution to a Modern Problem: https://www.youtube.com/watch?v=ZroDAyIqW74
With a little bit of heart, we can change the world -- biochar | Elaine Doyle | TEDxTallaght: https://www.youtube.com/watch?v=_19j0hEFVz0
Biochar - the future of sustainable agriculture: Lauren Hale at TEDxUCR: https://www.youtube.com/watch?v=AKBkgJoaIxQ&t=66s