Submitted to: Journal of Environmental Science and Health
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/7/2005
Publication Date: 1/20/2006
Citation: Loughrin, J.H., Szogi, A.A. Free fatty acids and sterols in swine manure. Journal of Environmental Science and Health part B, 41:31-42, 2006
Interpretive Summary: Fatty acids and sterols from swine manure are both a potential energy source and a potential source of pollutants. The amounts of these compounds were measured in fresh manure and manure storage lagoon sludge from swine production facilities in North Carolina. The fatty acids are liberated from fat in the swine diet whereas the sterols arise from bacterial modification of cholesterol and similar compounds in the diet. In general, fresh manure had greater amounts of fatty acids than did lagoon sludge, while the levels of sterols in fresh manure and lagoon sludge were similar. This indicates that sterols have greater persistence in the environment. In the case of fresh manure, fatty acids could be a resource for the manufacture of fuel if efficient means for their processing can be devised.
Technical Abstract: Free fatty acids and sterols were assessed in fresh manure and anaerobic lagoon sludge from swine production facilities in North Carolina. Eight free fatty acids and five sterols were identified and quantified in both manure and sludge samples. Compound identification was performed by gas chromatography/mass spectroscopy (GC-MS), and compound quantities were determined by gas chromatography after solid phase extraction with a 50:50 mixture of diethyl ether and hexane. The free fatty acids occurring in greatest abundance in both fresh manure and lagoon sludge were palmitic, oleic and stearic. Free fatty acid content in fresh manure ranged from approximately 3 'g g-1 dry weight (dw) to over 45 'g g-1 dw. In lagoon sludge, free fatty acid content ranged from about 0.8 'g g-1 dw to nearly 4 'g g-1 dw. Coprostanol and epicoprostanol were the sterols in largest concentrations in fresh manure and lagoon sludge samples. Total sterol content ranged from approximately 0.5 'g g-1 dw to around 11 'g g-1 dw in fresh manure and from 3.5 'g g-1 dw to almost 9 'g g-1 dw in lagoon sludge. Fresh manure and lagoon sludge both had high levels of inorganic cations (e.g. Ca, Mg, Fe) capable of binding free fatty acids and forming insoluble complexes, thereby potentially reducing fatty acid biodegradation. In anaerobic lagoons, sterols are an organic fraction of sludge that are resistant to bacterial degradation. In the case of fresh manure, fatty acids could represent a potential source of energy via the manufacture of bio-diesel fuel, if efficient means for their extraction and transesterification can be devised.