We investigated the effects of water loading, sludge moisture content, recovery solvent, and additives on the product yields and compositions from isothermal (673 K, 60 min) and fast (773 K, 1 min) hydrothermal liquefaction (HTL) of sewage sludge. The water loading (which affects pressure within the reactor) plays a small role in product yields. The sludge moisture content had a larger effect with the highest biocrude yields (26.8 wt% from isothermal HTL and 27.5 wt% from fast HTL) being produced from sludge that was 85 wt% moisture. The HTL biocrude from sludge mainly contains long-chain aliphatic hydrocarbon moieties and aliphatic acids. Dichloromethane recovered more biocrude and energy content (similar to 50%) than did the other solvents tested. Added K2CO3, Na2CO3, HCOOH, CH3COOH, MoO3-CoO/gamma-Al2O3 and Ru/C significantly decrease the biocrude yield when their loadings are 50 wt% of the dried sludge. The additives, excepting carbonates, enhance gasification of sludge. (C) 2017 Elsevier Ltd. All rights reserved.