Producing Stable Pyrolysis Liquids from the Oil-Seed Presscakes of Mustard Family Plants: Pennycress (Thlaspi arvense L.) and Camelina (Camelina sativa)

Natural oil from non-food oil seeds, such as camelina, jatropha, and pennycress, is increasingly becoming the feedstock of choice for biodiesel production through transesterification to fatty acid methyl esters (FAMEs) and green diesel via catalytic hydrotreating. Unlike the presscakes from food-based feedstocks, such as soy and palm fruits, the residual oil-extracted presscakes are often not suitable for consumption as animal feed. However, their abundance and the fact that these feedstocks are already collected give them a logistic advantage as a bioenergy resource over conventional lignocellulosic biomass, which is yet to be harvested. Vegetable oil-seed presscakes make an ideal thermochemical conversion feedstock because of their inherently high initial calorific value. We carried out fast pyrolysis of the entire value chain of two of the mustard family oil seeds, pennycress and camelina, and found that, at the optimum fast pyrolysis conditions, not only can high-carbon, high-energy liquid fuel intermediates be produced but also these liquids are low-oxygen, stable intermediates that do not oligomerize over time to higher molecular weight or increase in viscosity over time according to the accelerated aging test. Liquid fuel quality was high, with gross calorific value ranging between 29.0 MJ/kg for defatted oil to 34.7 MJ/kg for the whole seed on a dry basis. The corresponding carbon conversion efficiency, defined as feed carbon converted to the liquid pyrolysate, ranged between 60 and 80%. It is envisioned that co-location of a fast pyrolysis process with a green-diesel plant that uses these feedstocks could provide additional gallons of renewable biofuels and a reliable source of aromatic hydrocarbon compounds needed for the formulation of renewable jet fuels.