Efficiencies of unconventional bulking agents in composting food waste in Korea

Sawdust is the main bulking agent used to compost food waste in Korea but it is not an economically desirable choice because its availability entirely depends on imports. Since food waste composting provides agricultural, environmental and economic benefits, it is vital that we search for suitable replacements to sawdust from the locally available materials. In this study, we assessed the composting characteristics of food waste amended with various bulking agents including sawdust, ginkgo leaves, insect feces, and mushroom waste. Each of the bulking agents was mixed with the food waste in ratios of 3:7, respectively. Even though the initial temperatures were highest in the mixture of the food waste and insect feces whose temperature stood at 65 °C against 39, 58 and 51 °C in the sawdust, ginkgo leaves and mushroom waste mixtures, respectively on the third day of the experiment (DAT 3), it was terminated on the 21st day (DAT 21) because of excessively high water content (70.92%). The water content of the composted food waste supplemented with sawdust, mushroom waste, and ginkgo leaves stood at 51.28, 39.81, and 44.92%, respectively at the end of the experiment and therefore, the fully mature composts satisfied the water content requirement of less than 55% established by the Rural Development Agency of the ministry of Agriculture of Korea. The results of the CoMMe-101, Solvita and seed germination index indicated that the composted food waste amended with the mushroom waste and ginkgo leaves matured relatively quicker than that of the sawdust amendment. Based on the above observations, it is clear that the mushroom waste and ginkgo leaves are actually more effective bulking agents than the sawdust and as such, are recommended as suitable replacements for sawdust in food waste composting.