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Fats, Oils and Greases to Biodiesel: Technology Development and Sustainability Assessment

Tu, Qingshi
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1448037796

Abstract Details

2015, PhD, University of Cincinnati, Engineering and Applied Science: Environmental Engineering.
Fats, oils and greases (FOG) in the wastewater stream have long been a nuisance to the environment because they clog sewer pipes, causing overflows and damages. FOG can be classified as trap grease if obtained directly from food services, or sewer grease if mixed with FOG in the sewer system. This dissertation evaluated the technical feasibility and several sustainability parameters of converting trap/sewer grease into biodiesel. This waste-to-energy practice can provide the dual benefit of waste reduction and biofuel production. Monte Carlo simulations were conducted to model the energy consumption and GHG emissions from trap grease-to-biodiesel production life cycle at a wastewater treatment plant. Results were highly dependent on both the trap grease properties (e.g., FOG concentration, free fatty acid (FFA) concentration, etc.) and the utilization of non-lipid fraction of the FOG. Trap grease can provide lower energy consumption and lower GHG emissions for biodiesel production when compared to other feedstocks. This is particularly true for the trap grease with high FOG concentrations, low FFA concentrations, and a high performance anaerobic digestor (AD). As compared to other feedstocks, the probabilities that energy consumption of trap-grease biodiesel production life cycle would be lower were 46% (vs oil crops), 65% (vs waste cooking oil and animal fats) and 88% (vs algae). The probabilities were 89%, 67%, and 93%, respectively, when GHG emissions were compared. Of all the cases that energy consumption of trap-grease biodiesel was lower, the average reductions were 24% (vs oil crops), 36% (vs waste cooking oil and animal fats) and 73% (vs algae). When GHG emissions were compared, the average reductions were 76%, 54%, and 84%, respectively. Both sewer and trap grease have FFA levels higher than the acceptable level (15-20%) of the current biodiesel industry. Due to emulsion, the lipid fraction of the sewer grease cannot be directly obtained by heating. Two innovative technologies, glyceroloysis and in-situ transesterification, were tested to make biodiesel from these FOGs. The goal is to short circuit the solvent extraction process, which is impractical for the biodiesel industry. For trap grease, the results of glycerolysis showed that crude glycerin was effective in reducing the FFA% to < 1 wt% with an optimum condition of 230 °C for 150 min and 1:1 molar ratio between glycerin and FFA. The study on the time series of the mono-, di-, tri-glycerides (MAG, DAG, TAG), FFA and glycerin was conducted to better understand the reaction mechanisms, and the FFA reduction kinetics were estimated (as it fits the first order approximation). The advantages and disadvantages of this process were compared against the two-step process, an industry standard among biodiesel producers. For sewer grease, a direct transesterification process (in-situ conversion) was developed to extract the lipid and make biodiesel in one step. The optimum condition was determined as 20% (of dry sewer grease) H2SO4, 65 °C and 7hr, under which a 85.43% extraction rate (biodiesel+unreacted FOG vs. total FOG) and a 76% FOG-to-biodiesel conversion rate (biodiesel vs. total FOG) were achieved.
Mingming Lu, Ph.D. (Committee Chair)
Raymond L. Smith, Ph.D. (Committee Member)
Ting Lu, Ph.D. (Committee Member)
Timothy Keener, Ph.D. (Committee Member)
Drew McAvoy, Ph.D. (Committee Member)
262 p.
Environmental Engineering
Bidiesel; glycerolysis; in-situ conversion; Monte Carlo analysis; trap grease; sewer grease

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Citations

  • Tu, Q. (2015). Fats, Oils and Greases to Biodiesel: Technology Development and Sustainability Assessment [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1448037796

    APA Style (7th edition)

  • Tu, Qingshi. Fats, Oils and Greases to Biodiesel: Technology Development and Sustainability Assessment. 2015. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1448037796.

    MLA Style (8th edition)

  • Tu, Qingshi. "Fats, Oils and Greases to Biodiesel: Technology Development and Sustainability Assessment." Doctoral dissertation, University of Cincinnati, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1448037796

    Chicago Manual of Style (17th edition)

ucin1448037796
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This open access ETD is published by University of Cincinnati and OhioLINK.