Effect of turning frequencies on composting biodegradable municipal solid waste quality

The objective of this study was to investigate effects of turning frequency on physical, chemical and biological properties of municipal solid waste compost. A fixed turning frequency was compared with a temperature-controlled turning method. The moisture content of the treatments was adjusted to 50–60% in all cases. The results showed that the turning frequency significantly (P < 0.01) affected temperature, pH, total carbon, total nitrogen, the carbon to nitrogen ratio and the head weight of lettuce grown on the compost. However, the turning frequency did not significantly (P > 0.05) affect electrical conductivity. High losses of total carbon and nitrogen were observed in the frequently turned compost bin. However, high plant nutrient content and reasonable concentration of heavy metals with no restrictions for use in agriculture were observed in all bins except for Molybdenum in bin A (turned every time when the temperature either decreases or becomes constant for three consecutive days) and B (turned every week). Interestingly, plant growth bioassays indicated that the seedling emergences, head weight and leaf area of lettuces were higher in less frequently turned compost. Therefore, composting of municipal solid waste, in particular at a low frequency of turning, can be the best strategy to manage solid waste and boost agricultural productivity.

► Effect of different turning frequencies in composting biodegradable municipal solid waste was examined.
► Composting conditions for biodegradable municipal solid waste, in particular optimal conditions in view of compost quality and subsequent plant growth was evaluated.
► A less intensive turning frequency although delaying the composting process is more suitable for subsequential lettuce growth than more frequent turning.