Biological pretreatment applied to industrial organic fraction of municipal solid wastes (OFMSW): Effect on anaerobic digestion

The application of the anaerobic digestion for the treatment of the industrial organic fraction of municipal solid waste (OFMSW) has currently been of special interest. The main barrier in the treatment of this type or organic waste is its biotransformation, due to the complexity of organic material. Therefore, the first step must be its physical, chemical and biological pretreatment for breaking complex molecules into simple monomers, to increase solubilization of organic material and improve the efficiency of the anaerobic treatment in the second step. This article describes the application of biological pretreatment based on mature compost addition, in order to enhance organic matter solubilization and, hence, the biogas and methane production and the organic matter removal during the anaerobic digestion of the industrial OFMSW.Laboratory-scale experiments were carried out in semicontinuous completely mixed reactor, 5-L capacity. Optimal conditions for organic matter solubilization in the first step of pretreatment were: mature compost as biological agent, 2.5% (v/v) of inoculation percentage and 24 h as incubation period. The anaerobic digestion efficiency of the industrial OFMSW, with and without pretreatment, was evaluated for a solid retention time of 15 days. Under those conditions the organic matter removal percentage, in terms of eliminated dissolved organic carbon and volatile solids, was increased up to 61.2% and 35.3% respectively over the control without pretreatment. As consequence, the biogas and methane production are improved up to 60.0% and 73.3% respectively. The highest cumulative biogas and methane production under anaerobic digestion were obtained with pretreated waste: 178.6 L and 82.6 L against 61.6 L and 34.2 L of the control without pretreatment. The results have shown that biological pretreatment with mature compost, followed by dry-thermophilic anaerobic digestion, provides the best results for stabilizing the industrial OFMSW.

► The biological pretreatment with mature compost improves the OFMSW anaerobic digestion.
► The organic matter removal is improved up to 61.2% over the control without pretreatment.
► The biogas and methane production are increased up to 60.0% and 73.3% over the control.
► The specific methane production (LCH4/gTVSR) is improved up to 35.48%.