The advantages of composting are making full use of the organic
materials in waste, less secondary pollution and easy control.
Stones, metals and other wastes need to be sorted out before composting
since they are not broken down by microbes. If sorting is
incomplete and organic garbage mixed with metals garbage is
composted, many harmful substances will go into the soil with
compost, which will cause secondary pollution. Besides the technology
remains to be improved, the period of composting is long
and the area needed is large, which makes it is difficult to sell compost
(Awasthi et al., 2014)