Product distribution and implication of hydrothermal conversion of swine manure at low Temperatures

With the goal of utilization of agricultural wastes to produce valuable products, hydrothermal conversion of swine manure at 20% solids content was performed in a 2 L batch reactor at temperatures of 240°C to 280°C, 10 to 120 min reaction time, and 0.7 MPa initial pressure of nitrogen gas. Basically, four types of products (i.e., oil, aqueous product, solid, and gas) were collected from hydrothermal conversion of swine manure with primary material balance. Meanwhile, the raw oil product was distilled and extracted with toluene for accurately quantifying its oil, moisture, and solids content based on ASTM Standards. Results showed that oil yields from swine manure did not vary with reaction temperature and time used in this study, whereas the solid residue, aqueous product, and gas produced from swine manure changed as the temperature and reaction time increased. The results suggested that the hydrothermal conversion of swine manure to oil was a decarboxylation process with an oil yield of 33% by weight at 240°C, which was mainly attributed to the presence of other components in the swine manure, such as lipids, rather than direct hydrothermal conversion of cellulose to oil.