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Extraction of Lipids from Municipal Wastewater Plant Microorganisms for Production of Biodiesel
Author(s) -
Dufreche Stephen,
Hernandez R.,
French T.,
Sparks D.,
Zappi M.,
Alley E.
Publication year - 2007
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/s11746-006-1022-4
Subject(s) - biodiesel , transesterification , biodiesel production , extraction (chemistry) , pulp and paper industry , raw material , biofuel , methanol , chemistry , waste management , sewage sludge , acetone , wastewater , environmental science , sewage treatment , organic chemistry , catalysis , engineering
Municipal wastewater treatment plants in the USA produce over 6.2 × 10 6 t of dried sewage sludge every year. This microorganism‐rich sludge is often landfilled or used as fertilizer. Recent restrictions on the use of sewage sludge, however, have resulted in increased disposal problems. Extraction of lipids from sludge yields an untapped source of cheap feedstock for biodiesel production. Solvents used for extraction in this study include n ‐hexane, methanol, acetone, and supercritical CO 2 . The gravimetric yield of oil was low for nonpolar solvents, but use of polar solvents gave a considerably increased yield; however, the percentage of saponifiable material was less. Extraction of lipids with a mixture of n ‐hexane, methanol, and acetone gave the largest conversion to biodiesel compared with other solvent systems, 4.41% based on total dry weight of sludge. In situ transesterification of dried sludge resulted in a yield of 6.23%. If a 10% dry weight yield of fatty acid methyl esters is assumed, the amount of biodiesel available for production in the USA is 1.4 × 10 6 m 3 /year. Outfitting 50% of municipal wastewater plants for lipid extraction and transesterification could result in enough biodiesel production to replace 0.5% of the national petroleum diesel demand (0.7 × 10 6 m 3 ).