The method development SequEx: Bioavailability of trace elements for biogas production

The significance of the method of sequential extraction for the evaluation of the bioavailability of trace elements in biogas formation process was investigated by supplementation tests (batch tests and semi-continuous tests). According to their bioavailability, eleven nickel compounds were arranged in an order. The shift of nickel concentrations between the fractions while increasing the gas production rate determined by sequential extraction represents assumedly the adsorption process on the cell membrane. We found that the bioavailability of the trace elements in the successively extracted fraction does not decrease continuously, but it has to be evaluated element and time specific. Fermentation substrates used for the experiments were generated in test reactors by depleting only one trace element. Simultaneously the correlation between trace element supply, organic loading rate and trace element concentration was quantified. Furthermore storage stability of the samples, as well as the impact of extraction duration and temperature was examined.