This paper uses Marginal Abatement Cost Curves (MACCs) to illustrate the cost-effectiveness of mitigation potential offered by biochar projects compared to other mitigation measures. Biochar projects encompass a range of technologies, from wooden kilns to large processing plants. These projects differ in their abatement potential and implicit cost per tonne of carbon mitigated. Biochar stove and kiln projects in developing nations are more cost-effective than pyrolysis plant scenarios in developed countries, and thus could abate more fossil fuel carbon emissions (up to 1.03 Gt by 2030 in Asia). Even the most expensive biochar projects rival the cost-effectiveness of other carbon negative technologies such as Carbon Capture and Storage. Economic feasibility of all biochar projects depends on a range of factors including the price of carbon and significant ancillary benefits in terms of agricultural productivity. (C) 2010 Elsevier Ltd. All rights reserved.