Anaerobic digestion of pig manure fibres from commercial pig slurry separation units

摘要

The composition of manure fibres (MF) from 17 commercially separated pig slurries and seven raw pig slurries were characterised in terms of dry matter (DM), volatile solids (VS), protein, hemicellulose, cellulose and lignin. The average lignocellulose concentration in manure fibres and pig slurries was 790 and 370 g kg(-1) [VS] respectively. Biochemical methane potential was ascertained after 60 days, revealing a trend in biochemical methane potential between the different separation technologies used: pig slurry > shaking filter and screw press combined approximate to decanter centrifuge > flocculation, belt and screw press combined approximate to screw press. The maximum methane yield of manure fibres from decanter centrifuges and the combined shaking filter and screw press was approximately 330 l [CH4] kg(-1) [VS] at standard temperature and pressure (STP), while manure fibres from a screw press and a combination of belt press and screw press on average produced approximately 220 l [CH4] kg(-1) [VS]. Initial methane production can be described using a first-order kinetic model. The average rate constant for manure fibres was 0.030 d(-1) and for pig slurry 0.071 d(-1), showing that pig slurry is digested much faster than manure fibres