A Multi-criteria Decision Analysis of Co-substrate Selection to Improve Biowaste Composting: a Mathematical Model Applied to Colombia

Several physicochemical properties of biowaste can limit its composting. The incorporation of bulking agents (BA) and amendment materials (AM) is the most frequently applied operational approach to overcome such substrate limitations. This work proposes a decision model to optimally select bulking agents and amendment materials by applying a multicriteria analysis. The main objective of this study was to present a methodology to rank the co-substrates needed to compost biowaste. To accomplish this aim, an integrated hierarchy-based model was used that accounted for technical and environmental criteria. In particular, Analytical Hierarchy Process (AHP) and the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) were used to rank the potential co-substrates. The co-substrate ranking that was achieved with AHP and TOPSIS was then complemented by a cost analysis. The results of this study demonstrated the importance and the significant weight of the technical criteria, such as nutrients, porosity and biodegradability. The methodology was applied to a small town in Colombia that operates a biowaste composting facility. The results of the application of the tool in the above case study revealed that the most suitable materials for biowaste composting were sugarcane filter cake and star grass.