Changes in lipids and sterols during composting

Pyrolysis-gas (Py-GC) chromatography was used to characterize organic [(diethyl ether (DEE) and chloroform (CHCl3)] extracts of raw and composted duck excreta enriched wood shavings from two finishing cycles (C1 and C2). Materials were collected on days 0, 8 and 23. C1 contained 1.7 % total N while C2 contained 0.9 % total N. Py-GC-MS (mass spectrometry) showed that the extracts contained n-alkanes (C12 to C32), alkenes (C12:1 to C33:1), n-fatty acids (C12 to C28), unsaturated fatty acids (C18:1 and C18:2), and sterols (cholestene, cholestadiene, stigmastene, stigmastadiene, stigmastatriene, cholesterol, stigmastanol, stigmastanone, stigmastadienone, 17-methyl dialkylsulfanyl decahydro-1H-cyclopenta [a] phenanthrene, 17-methyl dialkylsulfanyl dodecahydro-1H-cyclopenta [a] phenanthrene, and 17-methyl-17-dialkylsulfanyl decahydro-1H-cyclopenta [a] phenanthrene). Other components identified were prystene, squalene (precursor of cholesterol), phthalic acid, diphenylpropane, diphenylbut-2-ene and 1,3,6 triphenyl hex-4-ene. Our data showed significant changes in the lipid composition of duck excreta enriched wood shavings during composting, which appeared to be related to the total N content of the system.