An industrial swine sludge and its blends with agricultural wastes from the oil industry were pyrolyzed in fixed bed and TG-MS units. Gaseous species were quantitatively analysed and the energy potential was evaluated. The biochars produced at different temperatures were characterized by physical and chemical analyses. Leaching experiments of biochar mixtures through soil predicted their suitability for soil amendment, as well as their environmental impact. The Higher Heating Value of the gases was found to be satisfactory for the energy requirement of pyrolysis units. Alkali metals Na and K and alkaline earth metal Mg were leached in high amounts through the soil, increasing the pH of the extracts and decreasing the leachability of heavy metals, which were below legislation limits. Biochars examined could be used as liming agents or for soil amendment providing plant nutrients. The waste materials examined could be valorized for energy and agronomic processes.