Methods of solid waste disposal

Solid waste is finally disposed of by one or more of the following methods, chosen according to waste type, land availability, cost and climate.

1. Open dumping: waste is thrown on open land without treatment. It is the cheapest, but causes odour, flies, rats, disease and water pollution; not recommended.
2. Sanitary landfill: waste is spread in layers, compacted and covered daily with soil, with leachate and gas control. Methods: trench, area and ramp (depression). It is the most widely accepted method of final disposal, including in Nepal.
3. Incineration: controlled burning at 800-1000 °C reduces the volume by 80-90% and kills pathogens; heat can be recovered. It is costly, causes air pollution and is unsuitable for wet waste; it is used for hospital waste.
4. Composting: biological decomposition of organic waste into compost (windrow, Bangalore, Indore, vermicomposting). It gives a soil conditioner but needs segregation.
5. Biogas / anaerobic digestion: organic waste is digested in the absence of air to give methane-rich biogas for cooking and electricity, plus slurry used as manure.
6. Pulverisation (grinding): waste is ground into small pieces and used as landfill cover or in compost; this reduces its volume.
7. Recycling and reuse: paper, glass, metal and plastics are recovered and reused, reducing waste (3R: reduce, reuse, recycle).
8. Dumping into sea/river: once used in some coastal cities (disposal by dilution), but now banned because it pollutes water; dumping waste into rivers is not allowed in Nepal.
9. Feeding to animals (hog feeding): food waste is fed to pigs after cooking; used in some places.

 waste -> segregation -> organic -> composting / biogas
                      -> recyclable -> recycling
                      -> residual -> landfill / incineration