Plate 1. The digester set up
Analytical methods
Samples from the manures were analysed at 105 oC dry weight basis for: total solids (TS) content (drying at 105 oC for 24 h); volatile solids (VS) content (ashing of TS at 550 oC for 5 h in a muffle furnace); total nitrogen (TN) content (regular-Kjeldahl method; (Bremner, 1996)); pH (1:10 w/v sample:water extract, using a pH meter, Model 8000). The total carbon (TC) content was estimated from the ash content according to the formula (Mercer and Rose, 1968):