Abstract
In this study, two types of sewage sludge (primary sludge and waste activated sludge) were hydrothermally treated at 125–250 °C to enhance the lipid extraction efficiency and obtain a higher biodiesel yield. The enhanced efficiency of the lipid extraction method was compared with the efficiency of the organic solvent extraction method. The results confirmed that a hydrothermal reaction could be an appropriate option for disrupting sludge cell walls and increasing the lipid extraction from sewage sludge. The highest lipid recovery efficiency was observed at 200 °C, and the lipid recovery efficiency of primary sludge and waste activated sludge increased from 7.56% and 5.35% to 14.01% and 11.55% by weight, respectively. Furthermore, transesterified lipids, such as biodiesel from sewage sludge, mostly consist of C16 and C18 methyl esters, and have features similar to those of jatropha oil-based biodiesel. During the hydrothermal treatment, the carbon content in the sludge decreased as the carbon transformed into lipids and the lipids were extracted. The volatile matter and fixed carbon content in the solid residue decreased and increased, respectively, through chemical dehydration and decarboxylation reactions under hydrothermal reaction conditions.
Highlights
IntroductionSewage sludge generation has increased with the demand for an improved quality of life
Sewage sludge generation has increased with the demand for an improved quality of life.Sewage sludge is a pollutant that affects human health and must be disposed of in an environmentally sound manner [1,2]
Sewage sludge with a certain level of lipid content has been considered as an attractive biodiesel feedstock
Summary
Sewage sludge generation has increased with the demand for an improved quality of life. Sewage sludge is a pollutant that affects human health and must be disposed of in an environmentally sound manner [1,2]. In recent years sewage sludge has gained attention as a promising source for biofuel production [3]. Many studies have suggested anaerobic digestion or fermentation and the direct use (through incineration after drying) of sewage sludge [4], but the low biological conversion efficiency and high energy consumption during sewage sludge drying are drawbacks of these methods. The high lipid content of sewage sludge has been gaining worldwide attention as a possible feedstock, owing to its low cost and availability, as it is an abundant organic waste [5].
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call