Thermochemical Processes Aimed at the Energy Valorization of Cow Manure from Feedlots

Abstract Disposing livestock wastes from concentrated animal feeding operations represents a problem from both economic and environmental care views, but it is possible to process them in thermochemical processes. The pyrolysis of cow manure was studied, with emphasis on the characterization of products. When the pyrolysis temperature increased from 550°C to 650°C, hydrocarbons yields increased 33% and char yields decreased 90%. Tar (the liquid product with the highest energy density) yields increased from 22 to 35 wt.%, and biooil (the product containing the highest amount of chemical compounds) yields were constant at about 27 wt.%. The biooil contained mainly acids, ketones, and furans, typical in the pyrolysis of cellulose, hemicellulose, and lignin, while the tar contained mainly alcohols and long-chain esters, derived from depolymerization and cracking of lipids and proteins. In comparison with other raw biomasses more extensively studied, cow manure produced much more tar, which could be important in, for example, bioasphalt formulations.