Currently, fossil fuels such as oil, coal and natural gas represent the main energy sources in the world. However, renewable energy sources, including biomass, have to be used to reduce environmental damage. Biomass wastes generated in the agricultural and agroindustrial activities are left in the field or discarded, usually without any value. In this paper a characterization as solid fuels of the main residual biomasses generated in Uruguay is approached. Six analyses were performed to characterize the biomass samples and their ashes: moisture, proximate and ultimate analysis, heating value, thermogravimetric analysis and ash melting temperature determination. It was found that olive and grape pomace have the best properties as potential fuels (even several properties better than some traditional fuels), followed by vine and olive prunings, then grape stems and switchgrass. On the other hand, cereal crop straws and wild cane did not show so favorable characteristics, specially heating values and ash contents.