POWER July 2010 - 76

COMMENTARY
WTE: Next-Generation
Sustainable Energy
By Dr. Marco J. Castaldi
I
t is clear that energy use will expand in the future as our
population and society's standard of living increase. Meanwhile,
the push toward a sustainable lifestyle requires that
all resources be utilized efficiently and sparingly. The National
Academy of Sciences has identified paradigm shifts from current
processes to an ideal vision centered on renewable energy
and an atom economy-defined as maximum incorporation of
starting materials into final products. These seemingly disparate
paths converge if one considers energy production from municipal
solid waste (MSW).
WTE's Renewed Popularity
Waste-to-energy (WTE) facilities in the U.S. have operated for
more than 30 years and in the past 15 years have been equipped
with the most advanced air pollution control systems, known as
maximum achievable control technology (MACT). Recently, these
power plants have gained renewed attention as communities
struggle with waste management and sustainability issues.
On April 13, the New York Times published the article, " Europe
Finds Clean Energy in Trash, but U.S. Lags. " It discusses WTE and
how Europe-in particular, Denmark-is a model that should be
followed when siting and operating WTE plants. In Europe, electricity
and heat for district heating from WTE facilities are used
to achieve overall thermal efficiencies of greater than 60%.
The typical question I hear after lectures and presentations
on WTE technologies is, " Why aren't we doing more of this? " The
simple answer I give is that preconceived notions, based on incinerator
emissions before the MACT regulations, have held back
development. But that is changing.
Overcoming Past Problems
Environmental groups and individuals that have resisted WTE
progress in the U.S. rely on outdated information and either refuse
to acknowledge, or are unaware of, the latest data and developments.
There was a time when MSW combustion facilities
were basically incinerators with inadequate emissions control and
low energy conversion. That was about the time automobiles still
used leaded gasoline and lacked airbags. Things have changed.
Currently, WTE facilities produce emissions well below the Environmental
Protection Agency's (EPA's) MACT standards. For example,
heavy metals like mercury are 85% below MACT and less than
2% of the mercury emissions of coal-fired power plants. Dioxin
emissions have been decreased by a factor of one thousand and
now represent less than 1% of the U.S. anthropogenic emissions.
Additionally, NOx
is about 15% below the EPA's limits and is considered
the last frontier for emissions reduction research.
WTE is perfectly aligned with sustainability efforts, as it has
been demonstrated that, on average, every ton of MSW combusted
in the U.S. produces 550 kWh, saves about 45 gallons of
oil or one-third of a ton of coal, and recovers about 50 pounds
76
of metal. Also, two-thirds of the carbon content of MSW is in the
form of biogenic materials such as paper and wood. It has been
estimated that for every ton of MSW that goes to WTE rather than
landfills, there is a saving of about one ton of CO2
.
Currently, WTE constitutes about 25% of the renewable energy
produced in the U.S. That percentage has the potential to grow
because only 7% of waste is converted to energy via WTE, 64%
is landfilled, and the remaining 29% is recycled. If all waste
were processed in modern WTE facilities, it could satisfy 3% to
4% of the country's electricity demand. The remaining ash can
be used in the construction and maintenance of landfills and as
an aggregate in construction. Moreover, the data show that communities
employing WTE have higher recycling rates.
WTE facilities in the U.S.
provide " baseload " electricity
without regard to prevailing
weather conditions.
WTE facilities in the U.S. operate at over 90% availability
(over 8,000 hours per year) and provide " baseload " electricity
without regard to prevailing weather conditions. Thus, WTE capacity
can be productively located in any region or state. Currently,
there are a total of 87 WTE facilities in the U.S. processing
about 28 million tons of MSW annually, supplying electricity to
more than 2 million U.S. homes and providing jobs to approximately
6,000 Americans.
A Promising Future
The need for WTE in the U.S. has never been stronger, yet most
WTE plants were constructed 15 or more years ago. This must
change, and indications are that it will. WTE is very favorably
viewed in Europe and Japan, and many other countries are exploring
WTE installations.
Encouragingly, WTE was identified among eight emerging green
technologies in a report from the Davos World Economic Forum
in 2009 entitled " Green Investing: Towards a Clean Energy Infrastructure. "
WTE was described as one of the emerging large-scale
sectors likely to contribute significantly to a future clean-energy
infrastructure, which included other renewables such as wind and
solar energy. To some of us, WTE is not " new " ; nevertheless, it fits
with these next-generation sustainable energy technologies. ■
-Dr. Marco J. Castaldi (mc2352@columbia.edu) is assistant
professor in the Earth & Environmental Engineering Department
at Columbia University in New York City. Much of the information
presented here was assembled by Columbia University's Waste to
Energy Research Technology Council (www.wtert.org).
www.powermag.com
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POWER July 2010

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