Extraction of oil from fish processing waste for fuel applications: process development, analysis and feasibility

Adeoti, Ibraheem Adetunji (2015) Extraction of oil from fish processing waste for fuel applications: process development, analysis and feasibility. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

The fish processing industry generates a significant amount of fish byproducts that could either be an important source of energy, food, or industrial feedstock. Fish oils are made up of several lipid classes. These lipids contain long-chain omega-3 polyunsaturated fatty acids; PUFA, (mostly eicosapentaenoic acid (EPA: C20:5 n-3), and docosahexaenoic acid (DHA: C22:6 n-3)) and other lipid classes. The traditional market for the nutritional lipids in the fish oil has been the food industry. However, significant infrastructure for the strict quality control systems is required for food grade oils. Therefore, the process of extracting the high nutritional oils is energy intensive. Further, the location and infrastructure limit the feasibility due to processing requirement, storage and/or transportation issue. For biofuel implementation, the processes to extract and refine fish oil are less energy intensive than the processes for nutritional quality oils and do not require the stringent product specifications and approval process as in the food and pharmaceutical industry. There have been significant advances in developing inexpensive and robust methods for fuel extraction and upgrading processes. Supercritical fluid extraction process using carbon dioxide (SC-CO₂) under moderate conditions is promising for quality fish oil production. This process produces oil with low impurities compared to other processes. The specific research objectives include: (1) Overview and background information on Atlantic Canada fish processing plants (2) Review of (state of art) fish oil extraction processes including physical, chemical and biological processes. (3) Fuel oil characterization of fish oil and fish oil blends with petroleum distillate. This section evaluates thermal stability, rheological, and heating values, of crude fish oil and blend with heavy petroleum distillate. (4) Solubility determination of fish oil in SC-CO₂; the SFE extraction process (optimize the SFE process conditions to maximize fish oil yield under the least intensive conditions, pressures, temperatures and CO₂ consumption); and mathematical model to predict oil extraction rate as a function of process conditions. (5) Fuel oil quality evaluation as a function of extraction methods. (6) Life cycle assessment (LCA) of different extraction processes (modified fishmeal process (MFM), SC-CO₂, and soxhlet processes) of fish oil from salmon wastes. The environmental burdens and potential impacts by each extraction process were quantified through the LCA. In the characterization phase of this study, the thermal and rheological properties of unrefined salmon oil, bunker fuel oil and their blends have been analyzed. The feasibility of using unblended and/or blends of fish oil in conventional heaters/boilers/engines are determined by these properties. The MFM oils, the bunker fuel oil and their blends behaved as a shear thinning non-Newtonian fluid that can be described by the power-law model. The supercritical carbon dioxide extraction (SC-CO₂) was effective at pressures of 15, 25, and 35 MPa, temperatures of 313, 333 and 353 K, and CO₂ flow rates of 0.18-0.48 kg/hr. The process is solubility controlled and the yields at 35 MPa, temperatures of 313, 333 and 353 K, and CO₂ flow rates of 0.18 kg/hr were approximately 39, 46 and 41 (wt.%). The mathematical model (Goto et al. 1993) using the best fit of theoretical extraction curve correlated the experimental data satisfactorily with average absolute deviation, AAD (%) ranged from 2.4 to 10.6 %. Unlike the MFM oil, the SC-CO₂ oil is more viscous homogenous oil which behaved as a Newtonian fluid. Physco-chemical, compositional and thermal characterization indicated SC-CO₂ oil contains fewer impurities than the MFM and soxhlet process oils. From the LCA results, the MFM method has the lowest overall environmental impact compared to the soxhlet and SC-CO₂ methods. The soxhlet extraction method, due to the use of solvent (hexane), has the greatest impacts on all of the four damage categories (human health, ecosystem quality, climate change and resources). The SC-CO₂ requires more energy to produce 1 kg fish oil (2 folds more than the MFM and 3 folds more than the soxhlet methods). However, the SC-CO₂ produces higher quality oil than the other two processes and the process impact on the environment is moderate relative to the MFM and soxhlet processes.

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