Efficient and sustainable recovery of lipids from sewage sludge using ethyl esters of volatile fatty acids as sustainable extracting solvent

• Published in: Fuel (Guildford) Vol. 295; p. 120630
• Main Authors: Villalobos-Delgado, Felipe J., di Bitonto, Luigi, Reynel-Ávila, Hilda E., Mendoza-Castillo, Didilia I., Bonilla-Petriciolet, Adrián, Pastore, Carlo
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.07.2021; Elsevier BV
• Subjects: Aluminum; Aluminum chloride; Biodiesel; Biodiesel fuels; Biofuels; Biolubricants; Biomedical materials; Calcium; Calcium soaps; Catalysts; Esters; Ethyl butyrate; Ethyl esters; Fatty acids; Green extraction; Lipids; Lubricants; Primary sludge; Resource recovery; Sewage disposal; Sewage sludge; Sludge; Soaps; Solvents; Volatile fatty acids; Water treatment; Water treatment plants; Biolubricants; Sewage sludge; Biodiesel; Calcium soaps; Green extraction
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2021.120630

[Display omitted] •Lipids can be extracted from primary sludge using green solvents.•Thermodynamic data from lipids extraction was used to obtain ternary diagrams.•Calcium soaps were efficiently recovered (~96%) by using ethyl butyrate.•Extraction performance can be easily predicted using ANN with R2 = 0.98.•Calcium soaps can be used as biolubricant or as source of biodiesel (yield > 85%). This work focuses on the recovery of resources from urban sewage sludge. Sewage sludge is generated by water treatment plants and contains a significant amount of lipids that can be used in a number of applications in fine chemistry. This study reports the extraction of lipids from sewage sludge using ethyl esters of volatile fatty acids as solvents. A thermodynamic study was first performed using synthetic primary sludge in order to identify the best operating conditions to apply on real samples of urban primary sludge. Ethyl butyrate showed the best separation performance. It was capable of efficiently recovering the lipid component from primary sewage sludge, which typically resulted in 13–23% of total solids. Highly pure calcium soaps can be extracted in high amounts (yield up to 93%), while the exhausted residual aqueous phase resulted as not significantly contaminated by the solvent and could be anaerobically digested easily. Finally, calcium soaps can be directly used as biolubricant or efficiently converted into biodiesel using aluminum chloride hexahydrate as a catalyst (yield 85%).