Valorization of cattle manure by thermoconversion process in a rotary kiln reactor to produce environmentally friendly products

Brazil has the world’s second largest cattle herd, which produces 1.9 billion tons of cattle manure per year. This work describes, for the first time, the processing of cattle manure by pyrolysis at 400, 500, and 600 °C in a rotary kiln reactor, as an alternative means of treating this waste to produce second generation biofuels. The biomass was mainly composed of hemicellulose (18.24%), cellulose (14.24%), and lignin (6.09%), with high ash content (18.86%). Pyrolysis of the cattle manure at 500 °C resulted in the best bio-oil yield (5.8% organic phase; 34.4% aqueous phase). The bio-oil consisted mainly of phenolic compounds such as phenol and 3-vinyl-phenol. The results for the biochar were indicative of its potential use in agricultural applications for correcting soil acidity. The biochars produced at higher temperatures presented a high degree of aromaticity, indicating the formation of a more stable material for the purposes of carbon sequestration.