Hydrothermal liquefaction of separated dairy manure for production of bio-oils with simultaneous waste treatment

A bench scale hydrothermal liquefaction (HTL) system was tested using dairy manure to explore biooil production and waste treatment potential. Carbon monoxide was used as the process gas and sodium carbonate (Na2CO3) as catalyst. At a 350 °C process temperature, the HTL unit produced 3.45 g (±0.21) of acetone soluble oil fractions (ASF), with an average Higher Heating Value of 32.16 (±0.23) MJ kg−1. A maximum ASF yield of 4.8 g was produced at a process temperature of 350 °C and 1 g of catalyst. The best ASF yield corresponded to 67.6% of energy contained in the raw manure. GC–MS analysis of ASF indicated that the highest quantities of phenolic compounds were formed when 1 g catalyst was used. Chemical Oxygen Demand (COD) reduction in the dischargeable slurry was as high as 75%. The results point to an alternative dairy waste treatment technology with a potential to generate transportable biooils.