The anaerobic digestion of organic matter in sugarbeet mud

Storage of sugar-beet mud in the traditional way, i.e., direct dewatering after pumping the slurry in storage basins, may cause odor nuisance because of digestion of organic substances. In order to prevent these bad odor problems the mud should remain submerged during the digestion period. No production of malodorous compounds was observed in this way, also not when after 1 yr of submersion the basins were dewatered and the mud began to ripen. Experiments were performed with small mud fields, barrels and pots in order to gain insight in the anaerobic digestion processes and to develop methods to optimize these. During these experiments the mud was subjected to a number of different treatments. No essential difference exists between the digestion process in dewatered and submerged mud. The digestion rate of the produced volatile fatty acids (VFA) depends on the growth rate of the bacteria responsible for the conversion of VFA into CH4 and CO2. This growth rate seems to be controlled in the pot experiment by the amount of available NH4-N. Treatment of the mud, for instance inoculation with old ripened mud or addition of carbonates, is only successful when the environmental conditions in the mud are very unfavorable for methane production (high VFA concentrations and low pH).