Different methods are used for treatment of solid waste and the choice of proper method depends upon refuse characteristics, land area available and disposal cost they are as follows
- Incineration
- Compaction
- Pyrolysis
- Gasification
- Composting
Incineration
It is a controlled combustion process for burning solid wastes in presence of excess air (oxygen) at high temperature of about 1000 Degree Centigrade and above to produce gases and residue containing non-combustible material.
One of the most attractive features of the incineration process is that it can be used to reduce the original volume of combustible MSW by 80– 90%.
Compaction
The waste is compacted or compressed. It also breaks up large or fragile items of waste.
This process is conspicuous in the feed at the back end of many garbage collection vehicles deposit refuse at bottom of slope for best compaction and control of blowing litter.
Pyrolysis
Pyrolysis is defined as thermal degradation of waste in the absence of air to produce char, pyrolysis oil and syngas, e.g. the conversion of wood to charcoal also it is defined as destructive distillation of waste in the absence of oxygen.
External source of heat is employed in this process. Because most organic substances are thermally unstable they can upon heating in an oxygen-free atmosphere be split through a combination of thermal cracking and condensation reactions into gaseous, liquid and solid fraction
Gasification
Gasification is a process in which partial combustion of MSW is carried out in the presence of oxygen, but in lesser amount than that is required for complete combustion, to generate a combustible gas (fuel gas) rich in carbon monoxide and hydrogen e.g. the conversion of coal into town gas.
When a gasifier is operated at atmospheric pressure with air as the oxidant, the end products of the gasification process are a low-energy gas typically containing (by volume) 20% CO, 15% H2, 10% CO2 and 2% CH4.
Composting
Composting is the most responsible technical solution for many developing countries especially, where the climate is arid and the soil is in serious need of organic supplements.
The composting process usually follows 2 basic steps, which may be preceded or followed by pre- or post treatments (crushing, sorting, humidification, mixing with other waste, etc…)