Environmental Engineering Reference
In-Depth Information
Chapter 1
B
IOGAS
R
ECOVERY FROM
L
ANDFILLS
1
Sherien A. Elagroudy and
2
Mostafa A. Warith
*
1
Civil Engineering Department, Ain Shams University Univeristy,
13 El-Makreezy Street, Manshiett Elbakry, Heliopolis, Cairo, Egypt, 11341
2
Ryerson Polytechnic University, Civil Engineering Department,
350 Victoria Street, Toronto, ON, Canada, M5B 2K3,
A
BSTRACT
Disposal of municipal wastes can produce emissions of most of the important
greenhouse gases (GHG). Solid wastes can be disposed of through landfilling, recycling,
incineration or waste-to-energy. This chapter will deal with emissions resulting from
landfilling of solid waste. The most important gas produced in this source category is
methane (CH
4
). Approximately 5-20 per cent (IPCC 1992) of annual global
anthropogenic CH
4
produced and released into the atmosphere is a by-product of the
anaerobic decomposition of waste. A major source of this type of CH
4
production is solid
waste disposal to land. In landfills, methanogenic bacteria break down organic matter in
the waste to produce CH
4
. In addition to CH
4
, solid waste disposal sites can also produce
substantial amounts of carbon dioxide (CO
2
) and non-methane volatile organic
compounds (NMVOC).
The gases produced in solid waste disposal sites, particularly CH4, can be a local
environmental hazard if precautions are not taken to prevent uncontrolled emissions or
migration into surrounding land. Landfill gas is known to be produced both in managed
“landfill” and “open dump” sites. Both are considered here as solid waste disposal sites
(SWDSs). Gas can migrate from SWDSs either laterally or by venting to atmosphere,
causing vegetation damage and unpleasant odors at low concentrations, while at
concentrations of 5-15 per cent in air, the gas may form explosive mixtures.
With the recognition of the formation of landfill gas and its associated hazards, and
the potential to utilize the energy content of the gas, the modern landfill site is designed
to trap the gases for flaring or use in energy recovery systems, particularly for the
