Effects of solids separation and time on the production of odorous compounds in stored pig slurry

Fresh pig faeces were separated into seven different liquid portions with particle size ranges < 2(.)0, < 1(.)4, < 1(.)0, < 0(.)5, < 0(.)25, < 0(.)15, and < 0(.)075 mm, respectively. Separation was achieved by consecutive sieving of the fresh pig manure through a series of seven American Society for Testing Materials (ASTM) standard wire screen sieves with openings of 2(.)0, 1(.)4, 1(.)0, 0(.)5, 0(.)25, 0(.)15 and 0(.)075 mm. The separated manure fractions were stored at an ambient temperature of approximately 20degreesC in Plexiglas columns (91 cm deep and 15 cm in diameter) to simulate storage in under-floor or in other types of holding pits. The results indicated that although solid-liquid separation was found to reduce production of volatile fatty acids (VFAs) and 5-day biochemical oxygen demand (BOD5) regarded as odour precursors, this technique might not significantly reduce odour nuisances from swine facilities unless particles smaller than 0(.)075 mm are separated from the liquids. Inverse linear correlations were observed between total solids (TS) and total volatile solids (TVS) with both BOD5 and VFAs and therefore their respective levels could also be used to quantify the potential of odour nuisances in stored pig manure. (C) 2002 Silsoe Research Institute.