ABSTRACT
The sources of solid waste are municipal solid waste (MSW), commercial solid wastes, construction/demolition solid wastes, sewage sludge from wastewater treatment plants, industrial solid wastes, agricultural solid wastes, and mining solid wastes. Approximately 60% of solid wastes go to the sanitary landfills, which are engineered systems, where the waste is deposited in compacted layers and covered with soil at the end of each day. To avoid the negative effects of landfill leakage and gas emission, the landfill has an impermeable liner on the bottom, as well as leachate and gas collection and treatment systems. Composting is an engineered biological system which performs the thermophilic and mesophilic aerobic decomposition of organic wastes. Windrow systems, aerated pile systems, and in-vessel systems of composting are used. Microbial succession during composting includes mesophilic phase with temperature from 20°C to 40°C, thermophilic phase with temperature from 60°C to 80°C, finished with cooling and maturation phases. The most active roles are played by thermophilic bacilli and actinomycetes. The major factors in composting are C:N ratio, intensity of aeration, temperature, and moisture content. A tutorial with solutions and a quiz bank are added to this chapter.
