Co-liquefaction of swine manure and mixed-culture algal biomass from a wastewater treatment system to produce bio-crude oil

This study explored the feasibility of combining two types of feedstocks, swine manure (SW) and mixed-culture algae (AW) from wastewater treatment systems, for bio-crude oil production via hydrothermal liquefaction. The effect of feedstock combination ratios on the bio-crude oil yields and qualities were investigated. SW to AW ratios (dry weight basis) were 1:3, 1:1 and 3:1 with a total solids content of 25%. Pure SW and AW were also hydrothermally converted at the same reaction condition for comparison. By combining 75% SW with 25% AW, the highest bio-crude oil yield was achieved (35.7% based on dry matter). By mixing 25% SW with 75% AW, the highest heating value (27.5 MJ/kg) was obtained. GC–MS spectra and thermal gravimetric analysis of bio-crude oils revealed that both light oils and heavy crude were produced, averaging 25% and 20% of the bio-crude oil, respectively. Analysis of energy consumption ratios indicated that co-liquefaction of AW and SW is energetically feasible and could be an economically competitive system for bio-crude oil production.