Writing in Environmental Science&Technology, Kelli Roberts and colleagues note that biochar is charcoal produced by heating wood, grass, cornstalks or other organic matter in the absence of oxygen. The heat drives off gases that can be collected and burned to produce energy. It leaves behind charcoal rich in carbon. Amazonian Indians mixed a combination of charcoal and organic matter into the soil to improve soil fertility, a fact that got the scientists interested in studying biochar's modern potential.
The study involved a "life-cycle analysis" of biochar production, a comprehensive cradle-to-grave look at its potential in fighting global climate change and all the possible consequences of using the material. It concludes that several biochar production systems have the potential for being an economically viable way of sequestering carbon — permanently storing it — while producing renewable energy and enhancing soil fertility.
Citation: Kelli G. Roberts et al., 'Life Cycle Assessment of Biochar Systems: Estimating the Energetic, Economic, and Climate Change Potential', Environ. Sci. Technol., 2010, 44(2), 827–833