Last reviewed 16 Sept 2026 · Facts as of 16 Sept 2026 · 10 min read
Solid waste
Solid waste is any discarded solid or semi-solid material arising from human and animal activities that is no longer wanted.
| Type | Sources / examples |
|---|---|
| Municipal solid waste (MSW) | Households, markets, shops, offices, institutions, street sweeping |
| Commercial and institutional | Hotels, restaurants, schools, offices |
| Construction and demolition (C&D) waste | Concrete, bricks, soil, steel, timber |
| Industrial waste | Process residues, packaging, fly ash, slag |
| Hazardous waste | Toxic, corrosive, flammable, reactive or infectious materials |
| Biomedical waste | Hospitals, clinics, laboratories |
| E-waste | Discarded electrical and electronic equipment |
| Agricultural waste | Crop residues, animal manure |
Terms: garbage — putrescible food waste; rubbish — non-putrescible combustible (paper, plastics, rags) and non-combustible (glass, metal) waste; ashes and residues; street sweepings; dead animals; bulky waste.
Characteristics of municipal solid waste
Composition (Indian MSW)
Indian MSW typically has a high proportion of biodegradable organic matter (often around half by weight), high moisture, a significant inert fraction (dust, sand, ash, debris), relatively low paper and plastics (though rising with urbanisation), and therefore low calorific value compared with waste in high-income countries. Per capita generation varies widely with city size and income.
Physical and chemical properties
Moisture content (wet-weight basis):
= initial (wet) mass; = dry mass after drying at 105 °C.
Density — varies with compaction: loose waste in bins, compacted in vehicles, and much higher in a compacted landfill.
Calorific value — modified Dulong formula (dry basis, % by weight):
C/N ratio — for composting, an initial C/N of about 25–30 : 1 is optimum.
Proximate analysis: moisture, volatile matter, fixed carbon, ash. Ultimate analysis: C, H, O, N, S and ash — used for combustion and composting calculations.
Functional elements of solid waste management
- Waste generation
- On-site handling, segregation, storage and processing
- Collection
- Transfer and transport
- Processing, treatment and resource recovery
- Disposal (of residues)
Waste management hierarchy (most to least preferred)
Prevention/reduction → Reuse → Recycling → Recovery (composting, energy) → Treatment → Disposal (landfill)
Integrated solid waste management (ISWM) combines these in a sustainable, cost-effective system.
Segregation, storage and collection
Solid Waste Management Rules, 2016 (key provisions)
- Waste generators must segregate waste at source into three streams — biodegradable (wet), non-biodegradable (dry) and domestic hazardous waste — and hand it over to authorised collectors.
- Sanitary waste (diapers, pads) wrapped separately; horticulture and garden waste stored separately; C&D waste managed as per its rules.
- Bulk waste generators must manage wet waste on site where feasible.
- No littering or burning of waste; user fees and spot fines by local bodies.
- Sanitary landfills only for residual inert waste and rejects of processing plants.
- Extended producer responsibility for packaging; related rules for plastic waste (Plastic Waste Management Rules, 2016 and amendments — including the prohibition of identified single-use plastic items from 1 July 2022).
Collection systems
| System | Description |
|---|---|
| Door-to-door collection | Primary collection from each household with segregated bins — best practice |
| Community bins / secondary storage points | Residents deposit waste; frequently overflow and cause nuisance |
| Hauled container system (HCS) | Containers filled at the site are hauled to the disposal/processing site, emptied and returned |
| Stationary container system (SCS) | Containers stay at the site; waste is emptied into a compactor vehicle |
Collection vehicles: handcarts and tricycles (narrow lanes), tippers, compactor trucks, dumper placers, hook loaders. Route optimisation reduces cost; collection is usually the most expensive element of SWM.
Transfer stations
Waste from small collection vehicles is transferred to large vehicles for long-distance haul to distant processing or disposal sites — economical when haul distances are long.
Processing and resource recovery
Materials recovery
- Material recovery facilities (MRFs) — manual and mechanical sorting of dry waste into paper, plastics, metals, glass for recycling.
- Separation techniques: trommel screens (size), magnetic separators (ferrous metals), eddy current separators (non-ferrous), air classifiers (light/heavy), ballistic separators.
- The informal sector (waste pickers, kabadiwalas) plays a large role in recycling in India.
Composting
Aerobic decomposition of biodegradable waste by microorganisms into a stable humus-like compost.
| Parameter | Favourable range |
|---|---|
| C/N ratio | About 25–30 : 1 initially |
| Moisture content | About 50–60% |
| Temperature | Thermophilic phase about 55–65 °C (kills pathogens and weed seeds) |
| Aeration | Turning of windrows or forced aeration to keep conditions aerobic |
| pH | Near neutral |
| Particle size | Shredded to increase surface area, but porous enough for air |
Methods: windrow composting (long piles turned periodically), aerated static pile, in-vessel composting, vermicomposting (earthworms — e.g. Eisenia fetida), home and community composting (pit, bin). The Indore and Bangalore methods are traditional Indian pit/heap methods.
Biomethanation (anaerobic digestion)
Wet organic waste (kitchen and market waste) digested anaerobically to produce biogas (methane and CO₂) and digestate (manure). Suitable for segregated wet waste from bulk generators and markets.
Thermal processing
| Process | Description | Remarks |
|---|---|---|
| Incineration (mass burning / waste-to-energy) | Controlled combustion with excess air; heat recovery for steam and power | Large volume reduction (about 80–90%); needs waste of sufficient calorific value and low moisture; strict air pollution control (dioxins, furans, particulates); ash disposal |
| Refuse-derived fuel (RDF) | Dry combustible fraction separated, shredded and dried for use as fuel in boilers or cement kilns | Improves calorific value; requires good segregation |
| Pyrolysis | Thermal decomposition without oxygen → oil, gas and char | Suited to specific streams (e.g. plastics, tyres) |
| Gasification | Partial oxidation with limited oxygen → combustible syngas (CO, H₂) | Higher efficiency; sensitive to feed quality |
Mixed Indian MSW with high moisture and inerts often has too low a calorific value for self-sustaining incineration without segregation and pre-processing.