Burning Garbage for
Fun and Profit
Suppose we had a
technology that could take any type of waste -- automobile tires,
landfill waste, hazardous PCBs, harbor sludge, steel scrap, and
more. And it could transform the garbage into a glassy,
obsidian-like stone a fraction of the size, which could be recovered
and re-used. Plus, the process also results in carbon and
hydrogen-rich gases that can burn like natural gas. Or the gases can
be processed further, refined through a membrane to make pure
hydrogen for fuel cells, the cornerstone of a future 'hydrogen
economy.'
Sound too good to be
true? Think again.
Often described as
'bottled lightning,' plasma-torch technology can do all that and
more. It works by passing an electric current through an ionized
gas, resulting in what scientists sometimes refer to as a 'fourth
state of matter' that often has temperatures hotter than the surface
of the sun. Stick virtually any kind of substance in the plasma
arc's path and it is irreversibly destroyed, broken down into heavy
metals and gases that can be recovered and reused.
And since the process
works without releasing contaminants into the atmosphere,
plasma-torch technology is catching on across the world, with new
plants opening in China, Italy, Hawaii and Japan.
First discovered by
German scientists in the 19th century, plasma torches and the
searing 5,000-degree-celsius heat they produce were used in the
1960s by NASA to simulate re-entry of spacecraft into Earth's
atmosphere. By the 1970s and 80s, scientists started looking into
the technology's potential for other sues -- like melting garbage.
Researchers started
vitrifying solid waste, melting out liquids and forcing out gases in
virtually any kind of material. The intense radiant energy and high
temperatures of plasma arcs essentially break down waste on a
molecular level, leaving little behind. A 1990 study in Canada found
that vitrified waste was 80 percent denser than the original
material, more than 90 percent smaller, highly stable and resistant
to leaching. Researchers soon envisioned metal tubes with electrodes
at either end to ionize gas and create plasma arcs. When inserted
into bore holes dug into landfills, the tube systems could literally
'shrink' layers of landfill material down to near nothing.
This is no small deal in
the United States, where more than 200 million tons of municipal
solid waste are dumped into landfills each year. As availability of
land grows more scarce and environmental and health laws governing
waste disposal become more stringent, plasma-torch technology could
start to look more and more attractive.
So why aren't plasma
torches being used in landfills across the country?
For starters, cost is a
major issue. At close to $70 per ton of garbage, plasma-torch
technology is easily double the price of cheaper methods such as
incineration and landfill disposal. But in locales where land is at
a premium, including Europe and Japan, plasma torches are being seen
as cost-effective for a variety of waste streams.
Japan, where the
government is looking to replace community incinerators with
alternative technologies, is at the forefront of plasma technology.
A new plasma waste plant that handles PCBs recently opened there,
and in 2002 Hitachi Metals helped build the country's first plasma
plant, which produces eight megawatts of electricity as a byproduct
of torching auto waste.
The other drawback to
plasma-torch technology is that is uses up almost as much energy as
it produce in combustible gases. But Joseph Longo of Startech
Environmental Corporation, a U.S.-based plasma torch developer, told
Planet Ark that a well-designed system can actually produce three to
four times as much energy in carbon gases and 50 percent more energy
than it uses in the form of hydrogen gas.
"If the energy in the
product gas stream is recovered and converted to electricity with an
efficiency factor of at least 25 percent, the total facility can be
self sufficient in terms of electricity. If the conversion factor,
or the relative proportion of energy out to energy in can be
improved for a given application, the system can be a net supplier
of electrical energy," reads the website of RCL Plasma, a Canadian
company focused on plasma gasification. "In key applications such as
the disposal of [municipal solid waste], a plasma gasification
system can almost always be capable of being a net supplier (rather
than consumer) of electrical power."
Besides the ability to
reduce waste to 90 percent less than its previous volume, the
capacity to generate its own power -- and potentially produce
surplus power that's fed back to the grid -- is enticing waste
managers to give plasma technology a closer look.
Presently, the cheapest
energy source for getting at hydrogen for use in fuel cells is
through fossil fuels such as coal or oil. But that entails all the
original environmental problems -- greenhouse gases, air pollution,
and toxins -- that gave rise to hydrogen as a desired alternative to
fossil fuels in the first place. As wind and solar power become more
directly competitve with other energy sources for producing
hydrogen, plasma torches might provide an 'in-between,' transitory
link in the chain of events leading toward wider adoption of
hydrogen.
According to Startech
Corp., which has a demonstration plasma torch facility as its
Bristol, Conn. headquarters, if the 225 million U.S. car tires
disposed of annually were instead zapped by Startech units, enough
hydrogen would be produced to supply 500,000 homes with electricity
for an entire year.
"Will it significantly
meet the needs of the U.S. for hydrogen? It will be one technology
of many," said Startech's Longo in Planet Ark.
So plasma torches may
turn out to be effective producers of hydrogen. But let's reconsider
waste reduction: If plasma can truly obliterate mad cow disease,
anthrax, low-level radioactive waste, PCBs and other hazardous
materials, are those materials really rendered inert in the glassy
rocks that the process produces? And are those rocks safe to be sold
for re-use in the construction and abrasives industries, as
researchers attest?
Thanks to work performed
at Washington's Battelle Pacific Northwest National Laboratory and
Integrated Environmental Technologies, a company based in Richland,
answers to such questions are emerging.
Researchers at PNNL and
IET, working with the proprietary "Plasma Enhanced Melter" system,
found that the obsidian-like rock is very stable, non-leachable and
non-toxic. And the Environmental Protection Agency recently backed
up that assertion. In a recent report, the EPA concluded that the
Melter system exceeded the agency's threshold for destruction of
hazardous materials by two orders of magnitude.
In the end, some might
knock plasma-torch technology by saying that it's nothing more than
a glorified incinerator, albeit a highly efficient one. And start-up
costs for many plasma facilities can run into the millions of
dollars, making the technology currently cost-effective for only a
narrow range of potential uses.
Plus, plasma doesn't
necessarily address the core problem of why we're running out of
landfill space in the first place -- all of our garbage. In fact,
one might argue that by zeroing out our build-up of waste, plasma
technology might actually encourage a continuation of our status
quo, throwaway mentality.
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