Agrochemical value of organic matter of fermenter wastes in biogas production

Abstract

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.

Anaerobic degradability of organic matter of cattle faeces and a possibility of its utilization

“…The situation is quite different if instead of the total quantity of the stable and labile fractions we examine the kinetics of their formation and express it by the rate constant of the labile fraction loss. For this purpose it is possible to in-vestigate the time changes in concentration during the oxidation of labile fractions as described by Blair et al (1995) or time changes during biochemical oxidation that we proposed for the evaluation of organic matter degradability in previous years (Kolář et al, 2006(Kolář et al, , 2008. The results of measuring the kinetics of oxidation degradation of stable and labile fractions and their ratio could partly replace the determination of anaerobic degradability at least in preliminary experiments and to make the operation of this research technology cheaper as we will prove in the nearest future.…”

The effect of fertilisation with digestate on kohlrabi yields and quality

“…Literature on the application of digestates as fertilisers for vegetables is very scarce. Expert opinion on the properties and possibilities for practical use of digestate as an organic fertiliser is divided (Odlare et al 2008, Kolář et al 2008, Möller et al 2011, Lošák et al 2011. Digestion is associated with large losses of organic carbon (C) (Möller 2009).…”

Utilisation of Waste from Digesters for Biogas Production

“…But its price is high, in the CR about 4 million Kč for the complex equipment. Hydrolytic methods require only a small amount of these costs and are quite satisfactory for practical operations (Koláį et al 2008). However, for scientific purposes we should prefer the methods that determine anaerobic degradability of organic matter, designated by D C .…”

“…This is the reason why the table below shows the original, not recalculated concentrations in the fugate of fermented substrate A and in the fermented liquid phases of the same substrate in IFBB conditions designated by B and C, which document considerable dilution of these potential mineral fertilizers. The solid phases of substrates A, B and C after anaerobic digestion were subjected to determination of organic matter hydrolysability in sulphur acid solutions according to Vallejo (2000, 2002) as modified by Shirata and Yokozawa (2006); we already used this method to evaluate the degradability of a substrate composed of pig slurry and sludge from a municipal waste water treatment plant (Koláį et al 2008 Table 8. Dry matter content in the fresh mass of used materials and their chemical composition in % dry matter.…”