Formulation of waste mixtures towards effective composting: A case study

Abstract

The main objective of this study was to evaluate the potential of organic waste streams for composting. For that purpose, different blends were used, with prevalence of waste-water treatment sludge, considering: 30 or 50% sludge and 50 or 70% of other wastes such as corn silage, expired animal feed and biomass ash. Composting in turned piles of around 1 m(3) was performed. The process was monitored during 73 days. The obtained product was analyzed regarding physical, chemical, microbiological and phytotoxicity parameters. The best results were obtained using 50% sludge, 30% of wood chips, 5% of ash, 5% of animal feed and 10% of corn silage; however, high losses of heat occurred, hygienization temperatures were not reached and thus microbiological parameters weren't fulfilled. A class II type of material (Decree-Law No. 103/2015 on fertilizing materials) is expected to be obtained at a higher scale.