Sanitary landfill: merits and demerits

A sanitary landfill is an engineered method of disposing of solid waste on land in which the waste is spread in thin layers, compacted and covered daily with soil, so that there is no nuisance or hazard to health or the environment. It differs from open dumping because it has a liner, leachate and gas control, and daily cover.

Methods

1. Trench method: used on flat land where the ground-water is deep; trenches about 2-3 m deep and 4-8 m wide are dug, and the waste is placed, compacted and covered daily with 15 cm of soil, using the excavated soil as cover.
2. Area method: used where the land is flat but the ground-water is high or the ground is rocky, so trenches cannot be dug; waste is spread on the ground surface in layers and covered with soil brought from elsewhere.
3. Ramp / depression (valley) method: used in valleys, quarries or ravines (common in Nepal, e.g. Sisdol, Banchare Danda); waste is spread on the slopes, compacted and covered.

 final cover 0.6 m
 ____________________________
 | daily soil cover 15 cm    |
 |  compacted waste cells    |
 |___________________________|
 clay/HDPE liner -> leachate collection pipe -> pond
 gas vent pipes

Operation: waste is spread in layers of about 0.5 m, compacted to reduce its volume, covered daily with 15 cm of soil, and finally covered with 60 cm of soil and vegetation. Leachate is collected and treated; methane is vented or flared.

Merits

• Cheap compared with incineration or composting; handles most kinds of waste.
• No odour, flies or fire if covered daily; the land can later be used as a park.
• Landfill gas can be used as fuel; flexible for varying quantities of waste.

Demerits

• Needs a large area of land, usually far from the city, so transport cost is high.
• Leachate can pollute ground-water; the gas (methane) causes a risk of explosion.
• The site settles, so building on it is restricted; there is public opposition to siting.