Evaluation of different sewage sludges as a potential biodiesel source in Japan

Wastewater treatment plants (WWTPs) are producing and treating ever-larger quantities of sewage sludge as urban populations increase in size. Sewage sludge contains lipids that can be transformed into biodiesel. We investigated sewage sludges obtained from two WWTPs (A and B) in Japan. Lipids were extracted via the Soxhlet hexane method and converted into biodiesel via acid-catalyzed transesterification. The primary WWTP A scum had the highest lipid and biodiesel yields (28.5% and 11%, respectively). Analysis of fatty acid methyl esters revealed that palmitic acid (C16:0), stearic acid (C18:0), oleic acid (C18:1), and linoleic acid (C18:2) predominated, regardless of sludge type. Analysis of sludge flow rates revealed that WWTPs A and B could produce about around 309 kg/day of biodiesel. About 74,000 tons/year of biodiesel could be recovered from primary wastewater sludge and scum in Japan.

Automated summary

Wastewater treatment plants produce a large amount of sewage sludge, which contains lipids that can be converted into biodiesel. This study found that sewage sludge from two WWTPs in Japan had high lipid and biodiesel yields when extracted and converted using specific methods.