Transformation means incineration, pyrolysis, distillation, or biological conversion other than composting;but transformation does not include composting, gasification, or biomass conversion.
Why transformation of solid waste?
There are several reasons as to why solid waste need to be transformed like efficient storage, handling and transport; reduce disposal cost; stabilize waste; destroy toxic elements (chemicals or biological entities); generate electrical energy as well as re-use.
Solid waste transformation involves three methods; physical; chemical and biological methods.
The physical transformations involves component separation or sorting: done mechanically or manually, at source or at a transfer station to recover recyclables and remove haz waste components; mechanical volume reduction or densification: done to reduce storage, transport and disposal costs. Here waste collection vehicles are equipped with compaction mechanisms; mechanical size reduction: makes waste more uniform and reduces the average size through shredding, grinding, and milling.
Biological transformations is applicable only to organic fraction of waste. The end product, compost is a humus like material used for soil conditioning applications or to produce methane gas.
Chemical transformations of solid waste typically involve a change of phase (example solid to liquid, solid to gas, etc.). To reduce the volume and/or to recover conversion products, the principal chemical processes used to transform Municipal Solid Waste include; combustion (chemical oxidation), pyrolysis and gasification.
Combustion (or chemical oxidation)
Combustion is carried out in the presence of enough air to oxidize the organic matter. Key products are N2, CO2, H2O, O2, ash, and heat is generated (exothermic reactions). Used for waste to energy plants
Pyrolysis is a thermal decomposition of organic material at elevated temperatures in the absence of oxygen (or...