The use of thermochemical and biological pretreatments to enhance organic matter hydrolysis and solubilization from organic fraction of municipal solid waste (OFMSW)

Abstract

The introduction of the anaerobic digestion for the treatment of the organic fraction of municipal solid waste (OFMSW) is currently of special interest. The main difficulty in the treatment of this waste fraction is its biotransformation, due to the complexity of organic material. Therefore, the first step must be its 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. The hydrolysis stage is considered the rate-limiting step for the anaerobic digestion of solid wastes. Thus, in this paper thermochemical and biological pretreatments were performed to accelerate the hydrolytic processes by means of a fast organic matter solubilization of industrial OFMSW. The thermochemical pretreatments were conducted in oxidizing and inert atmospheres and sodium hydroxide was employed as an alkaline agent. On the other hand, the biological pretreatments were performed using mature compost, fungus Aspergillus awamori and activated sludge from a conventional WWTP as enzymatic agents. The results from the thermochemical pretreatment indicate that the best conditions for organic matter solubilization were 180 °C, 3 g NaOH/L and 3 bar. Increments of soluble chemical oxygen demand (COD) of approximately 246% can be achieved in these conditions. In the case of biological pretreatments, the mature compost showed the maximum hydrolytic activity with an increase of COD of 51% for the lower inoculation percentage (2.5%, v/v).