Changes in some physical and chemical properties of fibrous solids from cow manure and digested cow manure during composting
Raviv, M.; Tarre, S.; Geler, Z.; Shelef, G.
Biological Wastes 19(4): 309-318
Fibrous solids mechanically separated from fresh cow manure (CMFM), thermophilically digested cow manure (TFM) and two-stage digested cow manure (TSFM) were composted for 7 weeks. During the composting period the general particle size distribution shifted from larger to smaller particles. In turn, the bulk densities and water retention characteristics increased. The C/N ratio narrowed to 30/1, 23/1 and 16/1 for CMFM, TFM and tSFM, respectively. The apparent nutrient deficiencies in CMFM and TFM, reflected in low electrical conductivity values, were also evident from the negligible ammonia levels at thermophilic temperatures and subsequent minimal nitrate concentrations at the end of the composting period. The rate of nitrification determined the rate of decrease in pH. The cation exchange capacity (CEC) for all the fibrous solids rose 30 meq per 100 g TS. A tomato plant growth experiment revealed that only TSFM behaved as the peat moss control.