Sustainable Pretreatment/upgrading of High Free Fatty Acid Feedstocks for Biodiesel Production PDF Download

Author: Majid Hosseini (Engineer)
Publisher:
ISBN:
Category : Algal biofuels
Languages : en
Pages : 157

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Book Description
The rationales of this research work were to investigate sustainable and environmentally friendly pretreatment processes that could be potentially viable in biodiesel production from cheaper feedstocks, also to examine less expensive harvesting techniques for collection of microalga Ochromonas danica (O. danica). To develop such sustainable pretreatment processes, the feasibility of upgrading waste cooking oil (WCO) using microalga O. danica was investigated. Two WCO samples with initial acid values (AV) of 10.7 and 3.9 (mg KOH/g) were examined. The AV of remaining oils was decreased by 2.8 and 2.4 mg KOH/g oil respectively. The fuel qualities of biodiesel made under the optimal conditions satisfied the standards of ASTM D6751. However, the yield and fuel properties (including the heating value) were better for the biodiesel prepared from the alga- treated WCO. Also evaluated in this study were two potentially less expensive flotation methods for harvesting the O. danica cells, one by micro-air bubbles and the other by droplets of WCO. According to the Taguchi method, the optimal condition for WCO-based flotation, in the test set-up used in this study, was 20 min for mixing duration, 20 min for flotation time, 420 rpm for mixing speed, and 10 (v/v)% of oil-to-sample ratio. Under this condition, over 80% of cells could be harvested with the floated oil layer. Oil residues remained in the processed water. Further water treatment might be necessary. Air flotation showed to be more effective. Performance, in terms of cell recovery and concentrating ratio, was best with stationary-phase cultures and at lower pH of 3.0-4.5. With proper increase of air flow rate along the flotation process, the recovery was consistently 90+% and could reach 98+% for samples of higher initial cell concentrations (> 1 x 108 cells/ml). As cells were responsible for foaming, the initial sample-to-column volume ratio should be lowered with increasing initial cell concentration (C0), so as to balance the foam generation (good for high recovery) with draining (good for high concentrating ratio). We also investigated the potential of a process based on complexation of the FFA in oil with aqueous solutions of multivalent cations. When maintained at 70° C for 4-6 h, oil-water mixture successfully separated into two phases with an inter-phase below the oil layer. The complexed-FFA was largely moved into the inter-phase and the aqueous phase while the oil layer with reduced FFA could be separated. Using CaCl2 as the complexing agent, the AV of the two selected oil samples in this study, having initial AV of 8.6 and 15.4 (mg KOH/g oil), were reduced to 3.2 ± 0.3 and 4.4 ± 0.2 (mg KOH/g oil) respectively. The FFA removal from oil would naturally lead to decrease (loss) of oil weight. The average oil loss (w/w) was 14 ± 1.4 % and 18 ± 2.2 % respectively, for the above two oil samples. When FeCl3 was used for complexation, the AV was reduced to 4.8 ± 0.1 and 6.5 ± 0.34 (mg KOH/g oil), and the average oil loss (w/w) was 10 ± 2 % and 14 ± 3 % correspondingly. The study results support the possibility of an integrated process of (1) removing FFA by complexation, (2) treatment of the FFA-containing water with the phagotrophic alga, and (3) harvesting the oil-laden algal cells with air flotation, as a potentially economic and environment-friendly process to upgrade the high FFA WCO for biodiesel production.