2.2 Conventional Approaches for Non-hazardous Solid Waste Disposal
35
2.2.1.2 Landfilling Environmental Emissions and Control
As described previously, a major problem from improperly managed waste in landfills
is the leachate generation, which is a significant threat to the surface- and groundwater and subsequently causing problems for plants and animals living downstream.
There are different leachate treatment technologies such as biological treatment,
carbon adsorption, nitrification/denitrification processes, chlorination, ion exchange,
chemical precipitation, biochemical treatment, pH adjustment, reverse osmosis and
ultrafiltration. Determination of the most effective treatment method depends on the
site specifications and requires detailed bench and pilot-scale testing [19]. Some
landfill sites use the method of evaporating the leachate fueled by the landfill gas.
However, this approach depends on the availability of a sufficient amount of landfill
gas, management of the resulting sludge and emissions as well as costs considerations
[19]. Sanitary landfills use liners and leachate collection and treatment systems to
control and prevent soil and water contamination and bioreactor landfills use leachate
recirculation as a liquid management technique [4, 19].
Landfill gas (mainly methane and carbon dioxide, and small amounts of nitrogen,
sulfur and oxygen and trace amounts of a wide range of other organic compounds) is
another source of contamination from landfills, which should be treated or managed
properly. Landfill gas can be recovered and combusted/flared or utilized as an energy
source by actively extracting it from the waste. Energy recovery can provide an
important potential source of renewable energy and reduce GHG emissions as a
result of lower fossil fuel consumption. The recovered energy could be in the form of
electricity, heat and production of pipeline quality gas of which the first two forms of
energy are the most commonly available landfill gas utilization options. Landfill gas
utilization depends on the cost of the operation, market pricing and availability of the
markets. In a conventional landfill with gas capturing and utilization equipment, only
around 60% of the produced methane over the life of the site is captured and the rest
is released into the atmosphere. In smaller landfills without gas capturing equipment,
all of the produced methane is released into the air. Sub-surface migration of the gas
is another option to reduce the potential environmental and health impact, which can
be done through an active collection of the gas or venting it from below the ground
into the atmosphere. However, venting the gas might have adverse effects such as
odor problems or air quality impacts [19].
2.2.2 Thermal Treatment
2.2.2.1 Thermal Treatment Technologies
Thermal treatment of waste is referred to the treatment or destruction of the waste with
temperature in the presence or absence of air, which convert waste into carbon dioxide
and water (via combustion or oxidation), liquid oils (via pyrolysis or hydrothermal
liquefaction), carbon monoxide and hydrogen gas (via gasification) [19]. Prior to
35
2.2.1.2 Landfilling Environmental Emissions and Control
As described previously, a major problem from improperly managed waste in landfills
is the leachate generation, which is a significant threat to the surface- and groundwater and subsequently causing problems for plants and animals living downstream.
There are different leachate treatment technologies such as biological treatment,
carbon adsorption, nitrification/denitrification processes, chlorination, ion exchange,
chemical precipitation, biochemical treatment, pH adjustment, reverse osmosis and
ultrafiltration. Determination of the most effective treatment method depends on the
site specifications and requires detailed bench and pilot-scale testing [19]. Some
landfill sites use the method of evaporating the leachate fueled by the landfill gas.
However, this approach depends on the availability of a sufficient amount of landfill
gas, management of the resulting sludge and emissions as well as costs considerations
[19]. Sanitary landfills use liners and leachate collection and treatment systems to
control and prevent soil and water contamination and bioreactor landfills use leachate
recirculation as a liquid management technique [4, 19].
Landfill gas (mainly methane and carbon dioxide, and small amounts of nitrogen,
sulfur and oxygen and trace amounts of a wide range of other organic compounds) is
another source of contamination from landfills, which should be treated or managed
properly. Landfill gas can be recovered and combusted/flared or utilized as an energy
source by actively extracting it from the waste. Energy recovery can provide an
important potential source of renewable energy and reduce GHG emissions as a
result of lower fossil fuel consumption. The recovered energy could be in the form of
electricity, heat and production of pipeline quality gas of which the first two forms of
energy are the most commonly available landfill gas utilization options. Landfill gas
utilization depends on the cost of the operation, market pricing and availability of the
markets. In a conventional landfill with gas capturing and utilization equipment, only
around 60% of the produced methane over the life of the site is captured and the rest
is released into the atmosphere. In smaller landfills without gas capturing equipment,
all of the produced methane is released into the air. Sub-surface migration of the gas
is another option to reduce the potential environmental and health impact, which can
be done through an active collection of the gas or venting it from below the ground
into the atmosphere. However, venting the gas might have adverse effects such as
odor problems or air quality impacts [19].
2.2.2 Thermal Treatment
2.2.2.1 Thermal Treatment Technologies
Thermal treatment of waste is referred to the treatment or destruction of the waste with
temperature in the presence or absence of air, which convert waste into carbon dioxide
and water (via combustion or oxidation), liquid oils (via pyrolysis or hydrothermal
liquefaction), carbon monoxide and hydrogen gas (via gasification) [19]. Prior to