As an environmental friendly and economical methanol for the fuel of a DMFC, we focused on a crude bio-methanol from woody biomass without refining. The effects of the impurities, i.e., ethanol, 1-butanol, methyl formate and diisopropyl ether, contained in the crude bio-methanol on the DMFC performance were investigated. Methyl formate and diisopropyl ether hardly or only slightly affected the DMFC performance, while ethanol and 1-butanol caused a significant degradation in the performance. When multiple impurities are present in the fuel as well as the crude bio-methanol, the degradation was somewhat lower than that of the single impurity, 1-butanol, which was the most harmful component of the multiple impurities. When using the crude bio-methanol as a DMFC fuel, removal of the harmful impurities, such as ethanol and 1-butanol, is necessary, otherwise a novel catalyst, which is also active for the oxidation of these impurities, required. (C) 2011 Elsevier B.V. All rights reserved.