AREA A/B ENGINEERING REPORT - Waste Management

Geosyntec Consultants
• Passive control with physical treatment: Alternatively, LFG may be passively captured
beneath the cover and treated by routing it through granular activated carbon to
physically bind and remove chemical compounds from the exit gas.
• Passive control with biological treatment: Examples include biowindows, biovents,
permeable reactive walls, and biocovers (see further discussion below), all of which are
engineered biologically active gas treatment systems through which LFG is routed and
within which the methane and noxious compounds in LFG are aerobically oxidized or
treated before the exit gas is safely emitted to the atmosphere.
• Passive control (no treatment): In many cases, LFG is of such limited volume, sufficient
control can be limited to installing a cutoff trench at the toe of the landfill to intercept
lateral subsurface migration.
Passive LFG management is generally used at
older landfills where LFG emissions are limited,
or at landfills that are too small to support
installation of an active GMS. Passive LFG
controls can function as a transitional
management strategy before discontinuing LFG
management during post-closure. Elements
common to all passive LFG management
strategies are that they utilize natural processes
and ultimately rely on the cover system as the
primary means of LFG control. Indeed, where
LFG generation rates are low, whole-site
oxidation of methane in LFG can be achieved
using an all-soil cover or gas management (or
Passive flare with solar powered self-ignition system.
(Photo courtesy of DSWA)
bioactive) cover in which a layer of highly-organic aerated soil or compost is included in the
uppermost layer of a composite, all-soil cover system.
Microbial oxidation (i.e. consumption of methane by bacteria in the presence of
oxygen to yield carbon dioxide and water) in biocovers represents an important
natural control on methane emissions in aerated landfill cover soils. As will be
described in Section 3.6.2, it has been observed that it is possible for cover soil
microbes to oxidize residual methane such that surface emissions are negligible. Manipulation of
landfill cover soils to maximize their oxidation potential thus comprises a large component of
passive GMS design. 17 Design of biocovers is thus best included as part of the overall design of
an alternative all-soil cover system.
17 A state of the art review of methane oxidation in landfill biocovers, and the design and performance of biocovers
and other biologically active gas treatment systems, is provided in Scheutz, et al (2009). Other key references
include Boeckx, et al (1996), Humer & Lechner (1999), Scheutz, et al (2003), Barlaz, et al (2004b), Gebert &
Gröngröft (2005), Abichou, et al (2006a and 2006b), Dever, et al (2007), Gebert, et al (2007), Kjeldsen, et al
(2008), Rachor, et al (2008), and Gamperling, et al (2008).
MD10186.doc 52 29 March 2009