The objective of the present paper is to contribute to the evaluation of quantity and quality of non-humified part of soil organic matter (SoM). in samples of soil organic matter from the humus profile of Šumava forest soils and forest meadows, taxonomically designated as mor and moder forms, the fractions of labile soil carbon C cws , C hws , C PM and fraction of stable carbon represented by carbon of humus acids C Ha and C Fa were determined. organic matter of samples was fractionated according to the degrees of hydrolyzability by two different methods in particle-size fractions of 2.00-0.25 mm and < 0.25 mm. The quality of labile fraction C hws was expressed on the basis of reaction kinetics as the rate constant of biochemical oxidation K bio and rate constant of chemical oxidation K chem of the first order reaction from a reduction in the concentration of C-compounds. The highest values of labile forms of carbon were determined in samples with the least favorable conditions for transformation processes of SoM, and these samples also had the highest content of labile forms in hydrolyses by both methods and the most labile fractions at the same time. The degree of SoM humification was strictly indirectly proportional to the lability of SoM and its hydrolyzability. The quality of labile fraction C hws can be expressed by both K bio and K chem while the sensitivity of K bio is higher but the reproducibility of K chem is better. K bio corresponds with the degree of SoM transformation, K chem with the proportion of C PM in total C ox .
Foodwaste (hereinafter, FW) is the most voluminous solid waste and its amount is growing rapidly all over the world. The turning of FW into biogas via anaerobic fermentation is widely recognized as an environmentally responsible and economically reasonable option. Based on the knowledge obtained from agricultural biogas stations, the current methods of FW fermentation management are based on balancing the ratio of total carbon and nitrogen. However, it was repeatedly and independently reported that the stability of this process is low, resulting in many concessions in terms of prolonged hydraulic retention time or reduced biogas yield. Hence, biochemical as well as economic performance of the process is balanced by mixing of FW with agricultural residues. FW samples of various origin were collected and biochemically analyzed. The data indicate that FW originating from homes and luxury restaurants tends to be lignocellulose-based, whereas the levels of crude fiber (25% up to 27%) are higher than those from agricultural feedstock (18%). In contrast, FW from school canteens and inexpensive restaurants tends to be starch-based with high levels of amyloids (21% up to 23%) and fat (5% up to 7%). A novel method better reflecting the bioavailability of carbon and nitrogen to anaerobic consortia is proposed. It is demonstrated that the previous optimization methods could somehow reflect the availability of nutrients in agricultural feedstock, as carbonaceous and nitrogen sources are relatively equally biodegradable. Nevertheless, the biodegradability of FW is considerably different, which is why higher amounts of proteins and lipids lead to increased levels of ammonia and sulfide, resulting in an inhibitory effect on the metabolism of anaerobic consortia. Optimizing the anaerobic fermentation of FW by the new method outperforms the previous technique and makes it possible to process FW more intensively, or, more precisely, with higher profitability and lower proportion of ballast agricultural feedstock.
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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