Aerobic solid-state fermentation of the solid fraction of pig slurry
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Current expansion in the pig number in Russia and their concentration in separate locations contribute to higher environmental risks. One key risk factor is the slurry produced. To utilize it more efficiently, many pig farms introduce its solid-liquid separation. The study objective was to explore the feasibility of accelerated aerobic solid-state fermentation of the solid fraction of pig slurry in closed installations. The stable thermophilic process under the temperature above +55 °C achieves shorter processing time of 3–4 days. To date, however, there is no representative evidence of such an experience. Four options of fermented mixture composition were tested based on two types of the solid fraction of pig slurry: Type 1 fraction coming from a screw separator and Type 2 fraction coming from a decanter centrifuge. The fermenter operating modes were tested in the authors’ previous studies associated with processing of the solid fraction of cattle manure and bedding poultry manure. The intensity measure of fermentation was the temperature reached by the processed material in the fermenter. Under the investigated operation modes, the stable temperature was observed for nine days in the mesophilic process: 20 °С to 55 °С; in some cases, the transition to the thermophilic process – above 55 °С was recorded. Adding the catalytic components to the processed material accelerated the substrate self-heating and a higher temperature up to 59 °С was reached. This suggests that the considered operating modes of the fermenter were suitable for the fermentation of the specified substrate.