Composting practice for sustainable waste management: a case study in Istanbul

Abstract: Increased demand in municipal and industrial facilities has caused growing number of solid wastes generation in the last decades. In this regard, it is necessary to develop sustainable management strategies for maintaining environmental quality. As a developing country, waste management is recognized as a priority issue in Turkey and new policies are in progress to overcome existing obstacles. According to the national strategy, it is planning to reduce the amount of biodegradable wastes to be disposed in landfill facilities by evaluating recycling, composting, or energy/material recovery methods. The aim of this study was to implement a composting system to a housing estate located in Istanbul for reducing organic waste loads to sanitary landfill areas and providing soil amendment for estate’s garden. In this scope, two compost tumbler systems with 1 ton/year capacity were set up in the pilot area. Kitchen waste was used in the first system and shredded before composting, whereas second system was only fed with yard wastes and tumblers were turned manually once a day. Final composts’ qualities were evaluated according to national regulations. Heavy metal concentrations of two composts were below the regulatory limits (Cd < 1 mg/kg, Co < 20 mg/kg, Cr < 100 mg/kg, Cu < 50 mg/kg, Mo < 10 mg/kg, Ni < 30 mg/kg, Pb < 50 mg/kg, Zn < 150 mg/kg). C/N ratios were calculated as 42.7 and 19.3 for kitchen waste and yard waste composts, respectively. According to the national regulations, C/N ratio of a final compost product must be <35. Therefore, it is suggested to use the mixture of these two types of composts for soil application.