Effect of Swine Manure Source and Storage Time on Bio-Crude Oil Conversion using Hydrothermal Process

摘要

Fresh and pit swine manures with different storage time were used as feedstock to investigate the effects of manure type and storage time on bio-crude conversion rates using a hydrothermal process. Both fresh and pit manures had been converted to bio-crude with refined oil yields of 32-42% (dry mass) of the total feedstock (~ 60-70% raw oil yield). The refined oil is the toluene soluble portion of the raw oil. The testing conditions were 305°C, with an initial solid content of 20% wt, a retention time of 30 mm, an initial N2 gas pressure of 0.65 MPa, and without catalysts or additives. Length of manure storage time in pit did not significantly affect the bio-oil formation compared to that of fresh manure, if the volatile solids contents were relatively similar. Manures from nursery, grower-finisher and sow pigs were tested, and statistical analysis showed that there were no significant differences of bio-oil yield for these different types of manures. A strong linear relationship was found between the refined oil yield and the sum of crude protein and crude fat contents in the feedstock. This indicates that the crude protein and crude fat are critical elements, although probably not the only two, causing bio-crude oil formation in the hydrothermal process.