Hydrothermal liquefaction (HTL) is a technology for converting algal biomass into biocrude oil and high-value products. To elucidate the underlying kinetics for this process, we conducted isothermal and non-isothermal reactions over a broad range of holding times (10 s-60 min), temperatures (100-400 degrees C), and average heating rates (110-350 degrees C min(-1)). Biocrude reached high yields (>= 37 wt%) within 2 min for heat-source set-point temperatures of 350 degrees C or higher. We developed a microalgal HTL kinetic model valid from 10 s to 60 min, including significantly shorter timescales (10 s-10 min) than any previous model. The model predicts that up to 46 wt% biocrude yields are achievable at 400 degrees C and 1 min, reaffirming the utility of short holding times and "fast"HTL. We highlight potential trade-offs between maximizing biocrude quantity and facilitating aqueous phase recovery, which may improve biocrude quality. (C) 2016 Elsevier Ltd. All rights reserved.