Field-to-Fuel Performance Testing of Lignocellulosic Feedstocks: An Integrated Study of the Fast Pyrolysis-Hydrotreating Pathway

Feedstock composition can affect final fuel yields and quality for the fast pyrolysis and hydrotreatment upgrading pathway. However, previous studies have focused on individual unit operations rather than the integrated system. In this study, a suite of six pure lignocellulosic feedstocks (clean (no bark) pine, whole-tree (including bark) pine, tulip poplar, hybrid poplar, switchgrass, and corn stover) and two blends (equal weight percentages whole-tree pine/tulip poplar/switchgrass and whole-tree pine/clean pine/hybrid poplar) were prepared and characterized. These materials then underwent fast pyrolysis and hydrotreatment. Although some feedstocks showed a high fast pyrolysis bio-oil yield, such as tulip poplar at 60%, high yields in the hydrotreater were not always observed. Results showed overall fuel yields of 17% (switchgrass), 20% (corn stover), 24% (tulip poplar, blend 1, blend 2), 25% (whole-tree pine, hybrid poplar), and 27% (clean pine). Simulated distillation of the upgraded oils indicated that the gasoline fraction varied from 39% (clean pine) to 51% (corn stover), while the diesel fraction ranged from 40% (corn stover) to 46% (tulip poplar). Little variation was seen in the jet fuel fraction at 11-12%. Hydrogen consumption during hydrotreating, a major factor in the economic feasibility of the integrated process, ranged from 0.051 g/g dry feed (tulip poplar) to 0.070 g/g dry feed (clean pine).