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Title:Towards transportation fuels via hydrothermal liquefaction of biowaste
Author(s):Watson, Jamison
Director of Research:Zhang, Yuanhui
Doctoral Committee Chair(s):Zhang, Yuanhui
Doctoral Committee Member(s):Yang, Hong; Cai, Ximing; Chen, Wan-Ting; Sharma, Brajendra K.
Department / Program:Engineering Administration
Discipline:Agricultural & Biological Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Hydrothermal liquefaction
biocrude oil
waste valorization
Abstract:This study explores techniques to enhance the production and quality of hydrothermal liquefaction (HTL) biocrude oil and aims to make it more amenable for conversion into transportation fuel. This area of research is becoming increasingly important because the establishment of a sustainable energy supply addresses national and energy security concerns. Furthermore, jet fuel is of particular importance because the U.S. Department of Energy asserts that the current global commercial jet fuel market (106 billion gallons) is projected to grow rapidly by the year 2050 (230 billion gallons). Unlike light-duty vehicles (cars, trucks, etc.) which can use low energy density fuel and batteries, airplanes will be likely constrained to using high energy density jet fuel. Airlines have committed to carbon-neutral growth starting in 2021. Thus, establishing cost-competitive and environmentally sustainable aviation fuel (SAF) has been recognized as essential to achieving carbon neutrality. This study incorporates chemical, biological, and physical techniques to augment the quality of HTL biocrude oil from biowaste and make it amenable for upgrading into transportation fuel. First, the extraction agent’s impact on the HTL product yield, characteristics, and energy efficiency was evaluated. Three representative extraction solvents (acetone, dichloromethane, and toluene) were chosen with three representative high-carbohydrate, high-protein, and high-ash content HTL feedstocks (Chlorella sp., Nannochloropsis sp., and Enteromorpha pr., respectively). Among the three solvents, dichloromethane exhibited the highest biocrude oil yield (dry biomass), net energy values, and fossil energy ratio values amongst all feedstocks. The solvent polarity, chemical structure, hydrogen bonding, and dipole-dipole interactions all could influence the HTL biocrude extraction (quantity and properties). Extraction solvent selection should be carefully considered and normalized for the reporting of HTL yields and energy recoveries. Second, a novel integrated process of biological (dark fermentation) and thermochemical (HTL) processes herein named DF-HTL, was investigated to enhance the yield and quality of HTL biocrude oil. Compared with the control, DF-HTL significantly enhanced the biocrude oil yield (wt.%), carbon content (mol), energy content (MJ), and energy conversion ratio by 9.8%, 29.7%, 40.0%, and 61.0%, respectively. Furthermore, this process decreased the aqueous by-product yield (wt.%), carbon content (mol), nitrogen content (mol), and ammonia content (mol) by 19.0%, 38.4%, 25.0%, and 13.2%, respectively. On the other hand, DF-HTL also augmented the nitrogen content (mol) of the biocrude oil by 42.2% in comparison to the control. The benefits of DF-HTL were attributed to the increased acid content, the incorporation of H2 as a processing gas, and the enhancement of the Maillard reaction which shifted the distribution of the HTL products from the aqueous phase to the biocrude oil phase. Third, fractional distillation was conducted to explore how physical separation of chemical compounds from biocrude oil could improve the biocrude oil properties, including the chemical (heteroatom content, energy content), physical (viscosity, density), and thermal (boiling point distribution, cetane value, cold-flow properties) properties. Distillates from HTL biocrude oil derived from food waste demonstrated increased H:C (4.2-13.7%) and HHV (4.1-21.3%) values. Furthermore, distillation decreased O:C (5.5-93.5%) and N:C (6.0-39.0%) values compared to the biocrude oil, leading to values similar to those of gasoline, diesel, and Jet A fuels. With respect to the physical properties, distillation decreased the density (23.8-30.5%) and viscosity (99.5-99.9%), while the acidity either increased or decreased depending on the distillation temperature range. Despite the benefits of distillation, blending was still required due to the poor N:C, viscosity, and acidity of the distillates. Finally, the stability of biocrude oil distillates derived from food waste was investigated in two distillation temperature ranges: low-temperature (199-238°C) and medium temperature (238-274°C) distillates. A stability study was conducted to understand the influence of storage conditions (headspace and temperature) on the distillate properties. Results demonstrated that the most positively impacted characteristics of the low-temperature distillates were the vacuum oil fraction (578.4-1,172.4%), distribution of compounds < 300 Da (633.3-780.0%), and the diesel fraction (542.6-765.3%). As for the medium-temperature distillates, the vacuum oil fraction (3,209.9-3,632.8%), distribution of compounds < 300 Da (580.8-741.0%), and the unsaturated hydrocarbons (48.5-75.4%) were the most positively impacted parameters. Comparing the treatment conditions, the storage temperature and headspace elicited different effects depending on the oil distillation range. Storage also decreased the O:C (21.6% and 86.5%), N:C (32.0% and 26.1%), and increased the HHV (3.1% and 10.8%) values in the low- and medium-temperature distillates, respectively. Furthermore, only slight deviations were observed in the density (5.2% and 7.4%) and viscosity (5.2% and 0.8%), respectively.
Issue Date:2021-11-22
Rights Information:Copyright 2021 Jamison Watson
Date Available in IDEALS:2022-04-29
Date Deposited:2021-12

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