Biochar technology has been proposed as a geoengineering solution that has potential to actively reduce the atmospheric concentrations of greenhouse gases and enhance the sustainability of agriculture. The magnitude of the technologies' net benefit must be considered in relation to the associated risks. Hazards posed by biochar technology need to be managed to a level that the resulting risks are deemed acceptable by society; identification of hazards is an essential first step. Effectively implemented risk management and sustainability guidelines, driven by informed policy directives, will result in biochar technology being an important tool for environmental and atmospheric greenhouse gas management.