Comparative studies of co-conversion of waste activated sludge and lignocellulosic wastes through hydrothermal liquefaction
Laleh Nazari, Haoyu Wang, Madhumita B. Ray, Chunbao Xu
Abstract
The effects of feedstock type on hydrothermal liquefaction were explored through the co-conversion of waste activated sludge and various lignocellulosic biomass sources, including birchwood sawdust, cornstalk, and waste newspaper. This investigation aimed to produce bio-oil under consistent conditions at 310 °C and a 10-min reaction time, with subsequent comparison to results obtained using single feedstocks. The co-feeding of sludge with cornstalk and sawdust demonstrated the highest bio-oil yields at 34.2 % and 33.7 % wt%, respectively. The comprehensive characterization of the bio-oil products revealed that feedstock type influenced elemental composition and, consequently, the higher heating value of the bio-oils. Bio-oils derived from co-feeds exhibited a significant presence of nitrogenous compounds, esters, and fatty acids in contrast to the high percentage of phenolic compounds found in bio-oils from single feedstocks. Furthermore, these co-feed bio-oils displayed lower molecular weights, higher quantities of low boiling point compounds, increased volatile matter content, and reduced fixed carbon content compared to bio-oils produced from single feedstocks. • Co-conversion of wastewater sludge and lignocellulosic biomass was investigated. • A maximum bio-oil yield in the range of 33–34 wt% was obtained using mixed feedstock. • Co-conversion resulted in higher quality bio-oils compared to single feedstock. • By-products of the process can be used for energy generation or as fertilizers.