Using biosolids as a water source in non-catalytic hydrolysis reactions for biofuel production

• Author / Creator

  Xia, Lin

• Biosolids are residues produced from the treatment of municipal sludge and are rich in organic materials. The growing volume of biosolids and concerns over microbial safety highlight the difficulties associated with biosolids disposal. Canada generates about 660,000 dry tons of biosolids annually,[1, 2] which is becoming an environmental issue. The biosolids used in this study are semisolids containing mostly water. Biosolids have difficulty settling, and the microbes and heavy metal content adds complexity to biosolids disposal. Furthermore, the cost of biosolids management accounts for more than half of the total operating cost of a wastewater treatment facility. Currently, solutions for safe disposal and utilization of biosolids have become ever more diverse, especially its application in energy recovery and biofuel production. A two-step lipid pyrolysis approach has been designed to be a sustainable biofuel technology that can widely use renewable lipid feedstocks. Thermal hydrolysis will convert lipids into protonated fatty acids, which later can be used as feedstock for pyrolysis to produce hydrocarbon-based drop-in fuels (Indistinguishable from petroleum-based hydrocarbons). Also, the hydrolysis process promotes the settling of biosolids. Several studies have investigated the thermal hydrolysis of brown grease with water, but nothing has been reported on using biosolids as the water source in the hydrolysis of brown grease. The primary goal of this study was to investigate the possibility of utilizing water and organic materials in biosolids for the hydrolysis process. The first objective of this research was to characterize the biosolids (water concentration >96%) and investigate the hydrolysis of unamended biosolids alone. The free fatty acids(FFA) in the hydrolysate were solvent extracted and analyzed to determine the impact of the hydrolysis on FFA %. The results showed that the quantity of lipid materials in biosolids following hydrolysis was too small but still can contribute for substantial hydrocarbon production. And the settling performance of the hydrolysates was excellent. In a second study, a renewable lipid feedstock, brown grease, was blended with biosolids to explore the hydrolysis performance of using biosolids as a substitute for water to hydrolyze brown grease, with regards to FFA% in the recovered lipid phase of hydrolysate and the FFA conversion. Different pH, reaction time, and temperature for hydrolysis were studied. The results showed the performance of the biosolids was similar to distilled water in terms of phase separation, FFA% and FFA conversion. The third research objective focused on the quality of the biosolids-hydrolyzed brown grease lipid phase influenced by the temperature. The hydrolysis was conducted at three different temperatures, starting from 280°C, and at a water-to-oil ratio of 5:1. Sulfur, nitrogen and other compounds were analyzed. Biosolids performed similarly to water in terms of free fatty acid conversion, but had slightly elevated sulfur and nitrogen content in the product.

• Subjects / Keywords

  • Brown grease
  • Biosolids
  • Biofuel
  • Non-catalytic

• Graduation date

  Fall 2017

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3513V908

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.