Statistical clarification of hydrothermal co-liquefaction effect and investigation on the influence of process variables on co-liquefaction effect

Hydrothermal co-liquefaction of different types of biomass has recently attracted great interest as it has potential to reduce logistics costs and increase biocrude yield/quality. Although positive co-liquefaction effect (CE) have been reported in previous studies, the statistical significance of CE is uncertain and the effects of process variables on CE remains unexplored. In this study, the carbohydrate-rich feedstock (sawdust & spent coffee grounds) was hydrothermally co-liquefied with algal biomass (Chlorella sp. & seaweed) at 270 °C and 320 °C with varying mixing ratio of 25:75, 50:50 and 75:25. A statistically sound method, one-sample t-test, was for the first time applied to evaluate if the positive or negative CE is significantly greater or less than zero. A significantly positive CE of 22.4% (synergistic effect) on biocrude yield was obtained in the co-liquefaction of spent coffee grounds/Chlorella sp. Co-liquefying sawdust/Chlorella sp. and spent coffee grounds/seaweed showed negative and positi...