SciDev.Net: Campaigners have launched a protest against a proposed form of geoengineering that they say is gaining popularity despite being untested and fraught with potential social and environmental repercussions. Biochar, at its most ambitious, involves recruiting vast amounts of biomass — for example, from dedicated plantations — and converting the carbon captured in the plant matter into charcoal. The charcoal is then ploughed into soils where it is hoped it will remain forever, improving …