Environmental Engineering Reference
In-Depth Information
provides a broad overview on Landfill gas (LFG) characteristics, composition, LFG
production and methods of enhancement, and gas yield. It also discusses gas-generation
mechanisms and gas-transport mechanisms and factors affecting both mechanisms.
Gases generated in the landfill will move throughout the mass of waste in addition to
movement or migration out of the site. Section 5 focuses on LFG movement and generation
and LFG monitoring programs. Landfill gas may form an explosive mixture when it
combines with air in certain proportions, LFG hazards including explosion, asphyxiation
hazards and odor are also discussed in this section.
Section 6 discusses LFG generation models. Several models are available for estimating the
LFG generation rate using site-specific input parameters. These models vary widely, not only in
the assumptions that they make, but also in their complexity, and in the amount of data they
require. The LandGEM model is one of these models and was developed by the US
Environmental Protection Agency to estimate landfill gas emissions and to determine regulatory
applicability to CAA requirements. There are other LFG emission models in use by industry
that also work very well. The Intergovernmental Panel on Climate Change (IPCC) methodology
for estimation of CH
4
emissions from the landfills is based on First-Order decay (FOD) method.
These 2 models are explained in details in this section. LFG regression models using site-
specific data are also discussed in this section along with mathematical models.
Section 7 provides an overview of landfill gas energy recovery system. The energy recovery
technology is based around the gas collection system and the pre-treatment and power generation
technology. Each of those three systems is explained separately in details in this section.
Section 8 covers the Calgary biocell as a full-scale case study that is constructed in
Calgary, Canada. It is a unique facility where the three processes, anaerobic bioreactor,
aerobic bioreactor and mining are sequentially applied in one cell. The stages of operation of
the cell and the LFG data collected over 2 years from the cell are provided in this section.
Anaerobic decomposition of organic solid waste in the landfill environment produces
landfill gas (LFG). LFG mainly consists of methane and carbon dioxide, both of which are
odorless. Trace constituents of other volatiles, often malodorous or toxic gases, are also found
in LFG. LFG can migrate through soil into structures located on or near landfills. Since
methane presents a fire or explosive threat, LFG must be controlled to protect property, and
public health and safety. Also, many jurisdictions require landfill owners/operators to reduce
reactive organic gas emissions to improve regional air quality. Thus, engineered solutions are
needed to efficiently and safely monitor, collect, and process landfill gas. As noted, a positive
side to LFG control is energy recovery. Today's technology allows a landfill owner/operator
to recovery the energy in LFG while reducing gas emissions. Revenue from the sale of LFG
or electricity generated using LFG as a fuel can offset costs for landfill environmental
compliance and/or closure.
II.
R
EGULATORY
C
ONSIDERATIONS
This section discusses environmental regulations as they pertain to landfill gas emissions.
Regulations addressed in this section include the European Landfill Directive [1999/31/EC],
Resource Conservation and Recovery Act (RCRA) solid and hazardous waste management
requirements, Clean Air Act (CAA) requirements, and Clean Water Act (CWA) requirements
