Interest in biodiesel research has increased over the years due to diminishing petroleum reserves but biodiesel has to be derived from non-edible oils in order to avoid the competition with food supply. Here, we report a one step catalytic conversion of non-edible seed oil, Calophyllum inophyllum with free fatty acid of 15% into biodiesel over biomass-derived catalysts. The effective catalysts were prepared by incomplete carbonization of carbon materials under inert atmosphere and then SO3H groups were introduced to obtain catalysts whose activities are comparable to conventional acid catalysts. At the optimized conditions, high conversion (99%) was achieved. The stability of the catalysts was also investigated. (C) 2013 Elsevier Ltd. All rights reserved.