Agrochemical value of organic matter of fermenter wastes in biogas production
2008
L. Kolář | S. Kužel | J. Peterka | P. Štindl | V. Plát
We performed 28-day mesophilic fermentation of a mixture of pig slurry and primary (raw) sludge from the sedimentation stage of a wastewater treatment plant at a 1:1 ratio. The components and the original and fermented mixture of slurry and sludge were subjected to acid hydrolysis. Dry matter of the solid phase of both components and both mixtures was incubated with sandy-loamy Cambisol at a weight ratio 3:1 at 25°C for 20 weeks; in 14-day intervals lipids, crude protein, hemicelluloses, cellulose, lignin, total nitrogen and hot-water-insoluble solids were determined. Changes in ion-exchange and buffering capacity of the test materials were recorded. Labile organic matters were determined after 20 weeks of incubation. Liquid fractions of both components and their mixtures were analysed before and after anaerobic fermentation. It was concluded that beneficial effects of wastes as fertilisers from anaerobic digestion could be attributed to their liquid fraction. After anaerobic digestion the solid fraction of these wastes has relatively increased ion exchange capacity as well as buffering capacity but it is very stable, hardly degradable organic matter, and therefore it cannot play the role of organic matter in soil. This is the reason why it should not be considered as an organic fertiliser.
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