In this study, the effects of product separation on the distribution of liquid products and the energy efficiency of sewage sludge liquefaction in supercritical alcohol and supercritical alcohol-water mixtures were investigated. While considering alcohol participation in the liquefaction reaction (6-47 wt%), the effects of process parameters such as temperature (300-400 degrees C), residence time (10-120 min), concentration (9.1-25.0 wt%), and type of supercritical fluid (water, methanol, ethanol, water-alcohol mixture) on the yield and properties of bio-oils were examined. Accounting for alcohol participation and product separation allowed the bio-oil yield, energy recovery, and energy efficiency to be newly defined. Application of the new separation protocol developed in this study realized a 10-25 wt% increase in bio-oil yield because light fractions were efficiently captured. When supercritical methanol was used, the light fractions consisted primarily of methylated short-chain esters, whereas ketones and alcohols were the major species when supercritical ethanol was used. Liquefaction at 400 degrees C and 20 wt% sewage sludge in a mixture of water-methanol (80:20, v/v) resulted in a bio-oil with a high calorific value (35.8 MJ kg(-1)), achieving 155% energy recovery and 106% energy efficiency. Computational fluid dynamics (CFD) analysis of bio-oil combustion conducted in a commercial boiler demonstrated that cofiring with a mixture of petroleum heavy oil and bio-oil resulted in a high firing temperature of 1570 degrees C and a heat transfer rate, which were comparable to that obtained from conventional heavy oil firing.