POWER April 2012 - 31

RENEWABLE ENERGY
As baseload, dispatchable units, WTE
plants continue to play an important role in
U.S. renewable energy generation, even accounting
for the fact that capacity has stagnated
and the EIA includes only the fraction
of output attributable to biogenic sources
such as green power. WTE technologies sup1.
Turning trash into treasure. At
waste treatment facilities, the tipping fees
offset the operation, maintenance, labor, and
capital costs of the facility along with the final
disposal costs of any unusable residues.
The fee can be charged per load, per ton, or
per item, depending on the source and type
of waste. This photo shows the Lee County
waste-to-energy facility's tipping floor, which
is the designated receiving area where waste
collection vehicles discharge their loads.
Courtesy: HDR Inc.
plied 15.4 TWh of renewable energy to the
grid in 2008, equivalent to 16% of nonhydro
renewable generation, second only to wind.
Of this total, MSW incinerators and fluidized
bed combustion (FBC) units produced
7.2 TWh from biogenic fuels, which make up
roughly 55% of the total U.S. waste stream
by heat input. Counting output attributable to
the combustion of plastics and other nonbiogenic
materials, these plants produced roughly
13 TWh, pushing overall generation from
WTE technologies above 20 TWh.
Independent power producers-among
them waste management firms and municipalities-own
the majority of load-serving
WTE capacity, while more than half of the
methane-rich fuel produced at U.S. landfills,
agricultural operations, and wastewater treatment
plants is applied to generate on-site heat
and power.
Conventional incinerators typically
collect MSW from a broad area, operate
on must-run status, and offer availabilities
exceeding 90%. LFG and digester
gas facilities-collectively referred to as
anaerobic-digestion-to-energy (ADTE)
plants-are distributed resources sited,
sized, and run according to fuel availability
and production rate. Both MSW-derived
fuels and digester gases may be cofired in
2. Benefits of expanding WTE deployment. Global adoption of integrated resource
management strategies could dramatically increase deployment of incinerators and advanced
conversion technologies. This development would reduce landfilling and associated emissions
of methane, while expanded landfill gas capture and energy production could further reduce the
carbon footprint of waste management practices. Source: Lauber & Themelis, 2010
Present
Future
fossil plants, but this may have operational
and regulatory implications.
MSW projects have a unique attribute: As
an alternative to landfilling, they typically
charge a tipping fee to municipalities and
other entities (Figure 1). This translates into
a negative fuel cost-and a revenue source-
that may help offset the high capital costs associated
with fuel handling and environmental
control systems and the high operations and
maintenance (O&M) costs attributable to the
variable composition, high moisture and ash
content, high contaminant level, and low energy
density of waste materials. ADTE plants
also require a steady supply of no-cost fuel to
justify the expense of collection, treatment,
and conversion systems.
The economics of WTE plants are extremely
site-specific, depending on tipping
fees, MSW characteristics, environmental
regulations, byproduct management practices,
and many other factors. WTE installations
often benefit from the investment and production
tax credits granted to renewable energy
sources. However, MSW plants sometimes
are granted no, or partial, incentives because
a significant percentage of their energy production
results from the combustion of plastics
and other nonbiogenic materials.
The economic viability of ADTE installations
is strongly influenced by policy drivers.
Policies requiring control of air pollutant
and greenhouse gas emissions from landfills,
agricultural operations, and wastewater treatment
plants improve economics by reducing
the incremental cost of adding generating
capacity. Depending on site-specific circumstances,
these projects also may yield revenue
streams in the form of marketable renewable
energy certificates and carbon credits.
Globally, more than 1 billion tons of postWTE
*800
plants
*160 million metric tons
*2000 plants
*400 million metric tons
Landfill
*1 billion metric tons
*300 million metric tons
Methane
emissions
*45 million tons
April 2012 | POWER
*5 million tons
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recycling MSW continues to be disposed of
in landfills each year, including more than
130 million tons in the U.S. While European,
Asian, and other nations move forward with
strong commitments to energy recovery, the
U.S. faces mounting MSW management
challenges, including the declining capacity
of existing landfills, growing opposition
to new disposal sites, high per-capita waste
generation rates, low recycling rates, and air
and water pollution concerns.
Electric Power Research Institute (EPRI)
modeling studies of the U.S. electric sector
performed using the National Electric System
Simulator & Integrated Evaluator (NESSIE)
project a fourfold increase in load-serving
MSW capacity to almost 9 GW and a threefold
expansion in load-serving LFG capacity
to more than 4 GW over the next two decades
under market-based climate policies.
Other countries that have not yet incorporated
energy recovery as a key component in
31

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POWER April 2012

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