Production of Biodiesel from Yellow Mustard Compatible with Food Protein Production
Keywords: acid-base-catalyzed transesterification
Dehulled yellow mustard flour
IPA extraction process
mixed alcohol transesterification
Mustard IPA/oil miscella
Ternary phase diagram

Mustard is produced in Canada in sufficient quantities that it can be used for both the food and fuel markets without having adverse agricultural effects. While mustard hulls are useful food ingredients, mustard seed oil is well-suited for use as a bio-fuel as it contains erucic acid, which is responsible for its high lubricity. Oil-seed extraction with IPA is an emerging alternative to hexane-based extraction due to its ability to eliminate the dangers associated with hexane processing while allowing recovery of high-quality protein products and vegetable oils. In this thesis, a novel rapid method for extracting oil from de-hulled yellow mustard flour using isopropyl alcohol (IPA) was developed. This method recovers the released oil in the form of a single-phase oil-IPA miscella. The extraction parameters that increase the oil yield without any loss or damage to the meal protein were ascertained followed by optimization of the direct ester formation from yellow mustard flour. The effect of process variables such as contact time, number of extraction stages, contact ratios, pH, temperature and water on extraction efficiency and miscella (IPA+oil) composition were examined. The results were used to develop parameters for an industrial process for oil extraction and increase the oil extraction yields. Multiple-stage extractions gave an oil yield of 94.7 % with a four stage extraction at a 2:1 IPA:flour (volume:weight) ratio at room temperature. At 45˚C, a 91.5 % oil yield was achieved with three stage extraction at a 2:1 IPA:flour (v:w) ratio. When compared with dry IPA, the oil yields determined from water-containing IPA extraction (13 % water) were lower by more than 40 %, the sugar content was nearly doubled, and the protein extraction did not change significantly in either single or multiple-stage extractions. Five rounds of recycling of IPA in the extraction process resulted in approximately a 1.4 % water increase in the recovered IPA, which is far below the water threshold determined to be 5% in this study. Therefore, the process and costs of dehydrating the IPA will not hinder the overall biodiesel production process or viability. The recovered miscella could be used in a direct ester conversion process to produce high-quality biodiesel. The IPA-extracted mustard oil had 3.53 ± 0.18 % and 2.61 ± 0.33 %, free fatty acid (FFA) and phospholipid contents respectively. The water content of the miscella was 2.13 ± 0.09 %, which was higher than the 0.3 % (w:w miscella) target for transesterification. Transesterification of the dehydrated miscella was performed using 1.2 % potassium hydroxide (w:w of the oil) as the base-catalyst at 72 ˚C for 2 hours and resulted in a relatively low isopropylester formation (29.33 ± 6.08 %). The addition of methanol to the miscella resulted in an oil conversion to ester of 86.96 ± 3.94 % at room temperature in 1hour. A phase separation technique was then developed in order to reduce the water and IPA content and the impurities of the miscella. The transesterification of the oil-rich phase separated from the miscella resulted in a 99 % ester. The recovery and recycling of IPA from the waste produced during the process was investigated in order to improve the efficiency and reduce the solvent cost of the overall system. A salting out method (using potassium carbonate) combined with azeotropic distillation, as well as pervaporation, was explored with the aim of recovering IPA during both the oil extraction and the transesterification process. Potassim carbonate was shown to be effective in modifying the liquid-liquid equilibrium of an IPA-water system in favour of IPA extraction from IPA-water mixtures. About 95 % and 96 % of the IPA (99% purity) was recovered from bulk solutions with 5 % and 13 % water contents, respectively, when using 20 % potassium carbonate (w:w). In azeotropic distillation, potassium carbonate was more effective in modifying the liquid-liquid equilibrium of an IPA-water system in favour of IPA extraction from the bulk solution (~99 % IPA extraction, ~94 % IPA content in the extract). IPA suitable for recycling into the oil extraction process (