Thermochemical conversion of swine manure: An alternative process for waste treatment and renewable energy production

A thermochemical conversion (TCC) process was applied to the treatment of swine manure slurry for oil production and waste reduction. The objectives of the first stage study were to explore the feasibility of oil production from swine manure and to determine the waste reduction rates through the TCC process. A bench TCC reactor was developed and tested at operating temperatures of 275 degreesC to 350 degreesC. The corresponding operating pressures ranged from 5.5 to 18 MPa. Carbon monoxide was used as a reducing agent at pressures from 0.34 to 2.76 MPa. The oil product was evaluated by element analysis, heating value, and benzene solubility. The waste reduction rate was evaluated in terms of chemical oxygen demand (COD) before and after the TCC process. The highest oil yield was 76.2% of the total volatile solids of the feed stock. The hydrogen to carbon molar ratio was 1.53. The TCC oil product had a similar quality as that of pyrolysis oils from liquefaction of other biomass such as wood sludge and newspaper waste. The average heating value of the oil product was estimated at 34 940 kJ/kg. The COD in the post-processed water after the TCC process was reduced as much as 75.4%. Carbon dioxide was the sole detected gaseous by-product. The solid by-product of the TCC process was only 3.3% of the total solids input by weight.