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Bioconversion of lignocellulosic biomass to bioethanol has shown environmental, economic and energetic advantages in comparison to bioethanol produced from sugar or starch. However, the pretreatment process for increasing the enzymatic accessibility and improving the digestibility of cellulose is hindered by many physical-chemical, structural and compositional factors, which make these materials difficult to be used as feedstocks for ethanol production. A wide range of pretreatment methods has been developed to alter or remove structural and compositional impediments to (enzymatic) hydrolysis over the last few decades; however, only a few of them can be used at commercial scale due to economic feasibility. This paper will give an overview of extrusion pretreatment for bioethanol production with a special focus on twin-screw extruders. An economic assessment of this pretreatment is also discussed to determine its feasibility for future industrial cellulosic ethanol plant designs.

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Recently, ionic liquids have been demonstrated to increase the efficiency of solvent extraction of lipids from microalgae. However, to date, mostly imidazolium-based ionic liquids have been investigated. This report extends the range of cations studied to over 30, including imidazolium, ammonium, phosphonium, and pyridinium derivatives, which were screened for their ability to increase hexane extraction efficiency of lipids from freeze-dried microalgae Chlorella vulgaris at ambient temperature. Promising ionic liquids were first identified using gravimetric analysis of total extractable oils. Oils extracted after ionic liquid pretreatment were further characterized with respect to fatty acid methyl ester (FAME) equal to biodiesel yield, FAME composition, and chlorophyll content. With few exceptions, all of the tested ionic liquids had lower chlorophyll content than standard solvent extraction techniques. The effect of process parameters such as mass ratio of algae to ionic liquid, incubation time, water content, and cosolvents were investigated for 1-ethyl-3-methylimidazolium ethylsulfate [C2mim]­[EtSO4]. The results indicate that this ionic liquid can disrupt C. vulgaris in conjunction with methanol and allow facile recovery of lipids over a large degree of dewatered microalgae (0–82 wt % water), in a small amount of time (75 min) at room temperature, resulting in the development of a low energy, water compatible, biodiesel production scheme.

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