Abstract
The accumulating volumes of biosolids in lagoons worldwide have intensified the need to develop innovative wastewater treatment strategies. Here, we provide proof-of-concept for the incorporation of biosolids into the hydrolysis step of a two-step thermal conversion of lipids for production of renewable hydrocarbons, which can be utilized as renewable fuels. Brown grease was hydrolysed with biosolids or water at 260–280 °C for 60 min at a mass ratio of 1:1 feed to water or biosolids. The feedstock and products were characterized using various analytical techniques to compare the performance of biosolids to water. The results indicated that there was no significant difference in the degree of hydrolysis of brown grease when biosolids was used as water replacement. The fatty acids composition after hydrolysis when biosolids was used as a water replacement also remained largely unchanged. Hydrolysis of brown grease with biosolids could be achieved at pH ranging from 3.3 to 8.9, and at a lower than previously established temperature. Significantly, the rapid settling of solid material in biosolids observed after thermal hydrolysis of brown grease may reduce the necessity of biosolids settling lagoons. Thus, incorporation of biosolids into a lipid hydrolysis-pyrolysis process may simultaneously benefit the biofuel and waste management sectors.Graphic
Highlights
Biosolids are the residues of wastewater treatment technologies and are typically stored in large settling lagoons that facilitate gradual thickening over a 1–4 year period [1]
The main focus of this research was to determine whether biosolids could be incorporated into lipid pyrolysis as a water replacement and a source of additional lipid material, we first examined the hydrolysis of biosolids themselves
Following thermal hydrolysis of the biosolids at 280 °C for 1 h, there was no significant difference in terms of ash content, but there was a small decrease in the amount of water, likely stemming from the consumption of water molecules during hydrolysis of lipids and other organic molecules or alternatively evaporative loss during handling
Summary
Biosolids are the residues of wastewater treatment technologies and are typically stored in large settling lagoons that facilitate gradual thickening over a 1–4 year period [1]. Chae et al described how thermal hydrolysis at 280 °C for 1 h dramatically increased the settling rates of biosolids and may serve as an alternative to using biosolids lagoons [8]. While some municipalities may have no other options than to employ an expensive process for the disposal of biosolids, the high capital and operational costs associated with thermal hydrolysis may be prohibitive in other towns and cities. An alternative suggested by Chae et al was to incorporate biosolids into existing high temperature processes, such as lipid pyrolysis [8]
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