Common renewable energy strategies can at best off-set fossil fuel emissions of carbon dioxide, but are not able to reverse climate change. One promising approach of lowering carbon dioxide in the atmosphere while producing energy is bio-char bio-energy based on low-temperature pyrolysis. This bio-energy technology relies on capturing the off-gases from thermal decomposition of wood or grasses to produce heat, electricity or bio-fuels.Bio-char is a significant by-product of this pyrolysis with remarkable environmentalproperties. Bio-char in soil was shown to persist longer and to retain cations better than other forms of soil organic matter. The precise half-life of bio-char is still disputed, however, and will have important implications for the value of the technology including carbon trading. In addition, the cation retention of fresh bio-char is relatively low compared to aged bio-char in soil and it is not clear after what period of time and under which condition bio-char attains its adsorbing properties. In order to maximize the favorable attributes of bio-char and fully evaluate environmental risks, research is needed at this critical juncture in the development of a bio-char bio-energy technology that has the potential to provide a significant carbon sink and to reduce environmental pollution by fertilizers.In a nutshell:• Current approaches to replace fossil fuel with renewable energy at best reduceemissions, but are unable to reverse climate change.• A new strategy obtains energy from gases produced by thermally degrading trees,shrubs, grasses, or organic wastes - very similar to charcoal making - in a processcalled pyrolysis. Charcoal or “bio-char” is left behind.• The proposed approach to combine pyrolysis for energy production with bio-charadditions to soil builds on its proven longevity and ability to retain cations betterthan other forms of carbon in the environment to actively draw carbon-dioxidefrom the atmosphere, regenerate degraded lands, and reduce environmentalpollution.• Precise knowledge of the longevity of bio-char and of the time and conditions todevelop adsorptive properties is needed to evaluate its economic andenvironmental benefits.• A full environmental risk assessment needs to be conducted to convincinglydemonstrate the level of emissions and lack of any soil contamination associatedwith the technology.