---
title: "Incineration: merits and demerits"
subject: "Sanitary Engineering"
chapter: 10
key: "semester_6/sanitary_engineering:solid-waste-incineration"
source: https://www.bctengineer.com/q/semester_6/sanitary_engineering/solid-waste-incineration
site: BCT Engineering
---

# Incineration: merits and demerits

Sanitary Engineering · Chapter 10: Solid Waste Disposal

- Asked in: 2077 Chaitra, 4 marks; 2076 Baisakh, 4 marks; 2073 Magh, 4 marks; 2072 Asoj, 4 marks; 2071 Bhadra, 4 marks; 2070 Bhadra, 4 marks; 2068 Bhadra (old course), 4 marks (asked 7 times)
- Video: [Advantages and Disadvantages of Waste Incineration | WELS (Waterpedia Environmental Learning Series)](https://www.youtube.com/watch?v=6vzcbgBAewU) — Waterpedia
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/sanitary_engineering/solid-waste-incineration
- Whole chapter: https://www.bctengineer.com/md/semester_6/sanitary_engineering/chapter-10

## Question

Explain the solid waste disposal by incineration along with its merits and demerits.

## Short answer

Incineration burns waste at 800–1000°C, reducing volume 80–90%. Ash residue is landfilled; heat may be recovered. It kills pathogens but has high cost, requires air pollution control, and is unsuitable for wet, low-calorific waste.

## Answer

**Incineration** is the controlled burning of solid waste at high temperature (800-1000 °C or more) in a furnace called an incinerator, which converts combustible waste into ash, flue gas and heat. It is used for waste that is combustible and has a high calorific value (hospital, pathological and hazardous waste), and in cities with little land.

#### Process

1. Waste is received in a storage pit and fed to the furnace by crane or conveyor.
2. The waste dries and ignites on the grate, then burns with excess air at 800-1000 °C; the flue gases are held at high temperature for about 1-2 s to destroy odours and toxic compounds.
3. The flue gas passes through a heat recovery boiler (for steam or electricity) and then a scrubber, filter or electrostatic precipitator before the chimney.
4. The residual ash and clinker (10-15% of the original volume, 25-30% by mass) are removed and landfilled or used in blocks.

```text
 waste -> [pit] -> [furnace 800-1000C] -> [boiler]
                       |                     |
                     ash/clinker     [scrubber/filter] -> chimney
```

#### Merits

- Volume is reduced by 80-90% and weight by about 70%, so little land is needed.
- Kills pathogens; suitable for hospital and hazardous waste.
- Heat can be recovered to generate steam or electricity.
- Can be located near the city, reducing transport; no odour or fly nuisance when operated properly.

#### Demerits

- High capital, operating and maintenance costs; needs skilled operators.
- Air pollution (dioxins, fly ash, SO₂, NOx) unless costly gas cleaning is provided.
- Not suitable for wet waste with a high organic content and low calorific value, as in Nepal (it needs auxiliary fuel).
- The ash still needs disposal, and non-combustibles (glass, metals) remain.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What is incineration?
   A. Burial in layers
   B. Aerobic decay
   C. Grinding
   D. Controlled burning at 800-1000 °C in a furnace
   Answer: D. It converts combustible waste to ash, gas and heat. (Key point: Definition)

2. Typical volume reduction?
   A. 80-90%
   B. 10-20%
   C. 40%
   D. 99.9%
   Answer: A. Volume falls by 80-90%, weight about 70%. (Key point: Volume reduction)

3. What follows the furnace?
   A. Direct chimney
   B. Boiler, then scrubber/filter, then chimney
   C. Landfill only
   D. Composting pit
   Answer: B. Heat recovery boiler and gas cleaning precede the chimney. (Key point: Heat recovery)

4. Why is it unsuitable for Nepal's waste?
   A. Waste is too dry
   B. Too much metal
   C. Wet, organic, low calorific value needing auxiliary fuel
   D. Waste volume is small
   Answer: C. High moisture and organic content lowers calorific value. (Key point: Demerit)

## Related in Sanitary Engineering

- [Methods of solid waste disposal](https://www.bctengineer.com/question.md?key=semester_6%2Fsanitary_engineering%3Asolid-waste-disposal-methods) — Sanitary Engineering, chapter 10, asked 2×
- [Composting: methods, merits, demerits](https://www.bctengineer.com/question.md?key=semester_6%2Fsanitary_engineering%3Asolid-waste-composting) — Sanitary Engineering, chapter 10, asked 5×
- [Sanitary landfill: merits and demerits](https://www.bctengineer.com/question.md?key=semester_6%2Fsanitary_engineering%3Asanitary-landfill-merits) — Sanitary Engineering, chapter 10, asked 4×
- [Sewer pipe materials: merits, demerits](https://www.bctengineer.com/question.md?key=semester_6%2Fsanitary_engineering%3Asewer-pipe-materials) — Sanitary Engineering, chapter 3
- [Importance and methods of waste management](https://www.bctengineer.com/question.md?key=semester_6%2Fsanitary_engineering%3Aimportance-waste-management-methods) — Sanitary Engineering, chapter 1, asked 7×

## Related in other subjects

- [Solid waste management system and techniques](https://www.bctengineer.com/question.md?key=semester_7%2Fenvironment_and_pollution_control%3Asolid-waste-management-techniques) — Environment and Pollution Control, chapter 5
- [Overvoltage causes; solid grounding merits](https://www.bctengineer.com/question.md?key=semester_6%2Fswitchgear_and_protection%3Aovervoltage-causes-solid-grounding) — Switchgear and Protection, chapter 5, asked 2×
- [Reactors in stations: merits and demerits](https://www.bctengineer.com/question.md?key=semester_7%2Fpower_plant_equipment%3Areactors-merits-demerits) — Power Plant Equipment, chapter 4
- [Physical and chemical characteristics of solid waste](https://www.bctengineer.com/question.md?key=semester_7%2Fenvironment_and_pollution_control%3Asolid-waste-characteristics) — Environment and Pollution Control, chapter 5