Effects of Alternative Process Gases on the Thermochemical Conversion Process of Swine Manure

A thermochemical conversion (TCC) process was developed to convert swine manure into an oil product in a high temperature and pressure environment. The objective of this study was to examine the effects of different process gases, including CO, H2, CO2, N2, and compressed air, on the efficiencies of oil production and waste reduction, and to explore the possibility of replacing costly reducing process gases, such as CO, with an inexpensive inert gas such as compressed air. It was found that the addition of a process gas to the reaction system before the experiment was critical for the TCC process to yield an oil product. Both reducing gases (such as CO and H2) and inert gases (such as CO2, N2, and compressed air) can be used as a process gas. With the addition of reducing gases (i.e., CO and H2), the process yielded a better quality oil product and achieved a higher oil production efficiency. There were no significant differences in the chemical oxygen demand reduction rate among the five process gases mentioned above. The pressurized process created by water vapor alone did not yield an oil product. It is unclear why the inert gases of N2, CO2, and compressed air affected the oil product formation from swine manure but water vapor did not.