In 2003, the Department of Environmental Protection, Taipei City Government initiated the kitchen waste reuse policy. Since then, kitchen wastes collected by the Taipei citizens have been required to be separated into the so-called “hog-feeding kitchen waste” and “compostable kitchen waste” before disposal. However, the amounts of the kitchen wastes collected these years have increased significantly. For example, in 2011 approximately 5,000 tons of kitchen wastes were collected each month in the Taipei City, and as high as 90% of the collected belonged to the compostable kitchen waste. Such massive production of kitchen wastes has become a crisis to the kitchen waste management for the City due to insufficient storage capacity, though there had been temporary storage areas specifically set up for the compostable kitchen waste in each of the three City-owned municipal solid waste incineration plants (MSWP), i.e., the Muzha, Beitou and Neihu plants.
The objectives of this study were to test the performance of vermicomposting on the acceleration of kitchen waste decomposition, and also to assess the possibility of replacing the current practice of kitchen waste composting in the temperate storage area of the MSWP with the vermicomposting approach. In doing so, the product quality of vermicompost was compared with that of the traditional compost in terms of fertilizing values and heavy metal contents. Additionally, the decomposition rate of the monthly input of compostable kitchen waste at the Muzha MSWP using the vermicomposting was simulated and evaluated.
Results of the 17-day experiment showed that compared to the traditional compost pile approach, vermicomposting had higher decomposition rates. However, while organic matter and nutrients increased in the vermicompost, the fertility of it was not superior to that of the compost resulted from the standard process suggested by the Department of Environmental Protection of the Taipei City. With regard to the application, the vermicomposting approach offered better performance than the traditional pile approach, particularly on the surface of earthworm activities. Regardless, given that the Muzha MWSP can utilize the entire 3-D volume of the temporary storage area for compost transformation, the overall volume reduction rate resulted from the traditional compost pile approach would be better than the vermicomposting approach.