ABC News - 26 Apr 09

Could Trash Solve the Energy Crisis?

Vaporizing Household Trash to Make Clean Energy: An
Environmentalists Dream, or Inefficient Garbage?

By PHIL MCKENNA
April 26, 2009

An engine known as a blowwer that acts as a vacuum to
extract gas from a landfill is seen at the Simi Valley
Landfill and Recycling Center in Simi Valley, Calif.,
May 8, 2008. A growing number of companies and research
groups around the world are working on gasification - a
process tht zaps household waste into energy and which, its
advocates say, produces few and no harmful emissions.
(AP Photo/Getty Images)

At first glance, 303 Bear Hill Road in Waltham, Massachusetts,
doesn't look like the scene of an environmental revolution. But packed
into a shipping container in the car park of this modest suburban
commercial building is a compact piece of technology that its maker IST
Energy insists can turn even the filthiest waste into clean, green
energy. "Trash will move from being a liability to an asset, providing a
clean source of energy that can be used right where it is produced,"
says Stuart Haber, the company's CEO.

IST is not alone in this revolution. It is one of a growing number of
companies and research groups around the world working on gasification -
a process that zaps household waste into energy and which, its advocates
say, produces few or no harmful emissions. Yet as pilot gasification
plants begin to spring up around the world, this apparent
environmentalist's dream is not being universally welcomed. Opponents
argue that the process is far from clean and that its track record in
terms of energy efficiency and emissions can hardly be considered green.
Not to mention the fact that it encourages the throwaway society that
the environmental movement has been trying so hard to get rid of. So
what is the real story? Is vaporising trash the answer to our energy and
waste-disposal woes, or an environmental wolf in sheep's clothing?

The idea of converting waste into energy has been around for decades.
Heat from garbage-fuelled incinerators can generate steam that drives a
turbine that in turn drives an electrical generator. Now fears over
energy security and climate change, combined with the rising cost of
dealing with the world's waste, are raising the possibility of disposing
of household trash using higher-energy methods once reserved for
hazardous materials such as medical waste and asbestos.

Gasification, and its cousin plasma gasification, involve heating
waste to a high temperature inside a sealed chamber. This is done in the
near absence of oxygen, so organic components in the waste do not burn
but instead reform into syngas, a mixture of carbon monoxide and
hydrogen. This can be filtered and chemically "scrubbed" to remove toxic
particles and gases, and then burned to produce energy or converted into
other fuels such as methane, ethanol or synthetic diesel. All that's
left to dispose of at the end is ash, dirty filters and chemicals from
the scrubbing process, which can be treated and sent to landfill or into
the sewers.

Gasification yields more energy per volume of trash than
incineration, but the possibilities don't end there. Adding an arc of
superheated plasma to the mix can increase that yield further. Plasma
gasification vaporises waste at much higher temperatures - up to 10,000
°C compared with up to 1600 °C for normal gasification - which ensures
that more of the organic waste is gasified.

In this kind of gasification, plasma arcs are created by passing a
high-voltage current through a chamber filled with an unreactive gas
such as nitrogen (see diagram). As the current flows through the
enclosed space, it tears electrons from the gas to form a superheated
plasma that rips apart the molecules in whatever is fed into the
chamber. "It's like a continuous bolt of lightning that disintegrates
almost anything that crosses its path," says Daniel Cohn of the
Massachusetts Institute of Technology, who has been working on plasma
gasification since the 1980s and now sits on the board of InEnTec,
another waste-to-energy company.

A further advantage of this technique is that the very high
temperatures cause the waste to end up not as fine ash but as a glassy
solid, which could in principle be used as filler in the construction
industry. And while the power required to run InEnTec's pilot plant in
Richland, Washington, amounts to one-third to half of the power it
produces, Cohn insists that the process is financially viable. He says
syngas can be converted to ethanol and synthetic diesel at costs that
can compete with petroleum-based equivalents. "We think we can produce
fuel at a cost of about $2 a gallon of gas equivalent," he says. If he's
right, trash could become the new oil.

Pilot gasification plants are being set up at various sites in the
US, Canada, France, the UK and Portugal, most of them using the plasma
technique. Japan already has two commercial plasma plants, but these are
focused primarily on simply disposing of household waste rather than
generating energy from it.

While these new plants will all be large installations, IST Energy
believes that small is the way to go. Its container-sized non-plasma GEM
system (short for Green Energy Machine) can convert almost 3 tonnes of
municipal waste a day into enough syngas to heat and power an office
building holding 500 people.

Keeping the system small and avoiding the expense of creating plasma
makes it affordable for businesses to deploy: excluding the gas burner,
the system costs $850,000 and, according to Haber, will pay for itself
in four years through savings on electricity, heating and waste disposal
charges.

Haber says the entire system can save the equivalent of about 500
tonnes of carbon dioxide emissions a year through reductions in landfill
gases, fossil-fuel use and the transport of waste. Haber also claims
that, compared with traditional incineration, the quantity of toxic
gases produced by the GEM system is negligible. "It's really a
night-and-day difference," he says.

Gasification is not without its detractors, partly because early
attempts to gasify garbage were environmentally and financially
disastrous. A series of economic and environmental problems at an early
commercial gasification plant in Karlsruhe, Germany, including a leak of
toxic gases that temporarily closed the plant in 2000, caused the
facility to shut down for good in 2004. These troubles have tainted the
reputation of gasification - and, by association, plasma gasification -
ever since.

One objection that sceptics raise is that gasification still produces
CO2 emissions. Neil Tangri of the Global Alliance for Incinerator
Alternatives (GAIA) dismisses gasification plants as glorified
incinerators. "There is an intermediate step with gasification, but the
end result is always combustion," he says.

Another concern is that the waste gas from gasification may contain
dioxins, which form when organic material is heated to high temperatures
in the presence of chlorine-containing compounds, which are ubiquitous
in municipal waste.

"Any attempt to turn garbage into energy will most likely cause the
production of significant amounts of dioxin, which many consider the
most significant carcinogen known to science," says Ron Saff, a
physician in Tallahassee, Florida, and a member of Physicians for Social
Responsibility.

Clean and green? Others say that chlorine can cause an additional
problem in the extremely hot, oxygen-starved environment of a plasma
gasification chamber. "If you pass mixed waste with chlorine in it
through a plasma arc, you get metal in the [syn]gas that otherwise
shouldn't be there," says Thomas Cahill, an emeritus professor of
physics and atmospheric science at the University of California, Davis.
These metal pollutants could escape into the environment when the gas is
burned, he argues.

Companies already running gasification systems point out that the
process is as clean as you make it: what matters is how efficiently the
syngas is scrubbed and how effectively the ash is disposed of. They also
say that they operate to strict national or regional standards governing
emissions from waste-to-energy power generation.

"The regulations that they have to comply with are much more
stringent and focus on a wider range of toxins than for a conventional
power plant," says Marc Wolman of the Massachusetts Department of
Environmental Protection in Boston. "If they don't meet these limits
they get shut down, period."

On the issue of dioxins, at least one waste-to-energy company is
making reassuring noises. Andreas Tsangaris of the Plasco Energy Group
in Ottawa, Canada, which has been running an 85-tonne-per-day
waste-to-energy pilot plant since September 2007, says: "We remove
virtually all the chlorine before combustion. There is no chance for
dioxins to form." The company's own monitoring shows that its emissions,
including those of dioxins and heavy metals, have remained at or below
the most stringent regulatory limits in North America and Europe.

Nevertheless, a newspaper article by Cahill, based in part on his
studies of emissions from the smouldering remains of the World Trade
Center in New York - which he says are "eerily similar" to those from
gasification plants - plus a strongly worded editorial by Saff, had a
direct impact on two proposals for high-profile commercial plasma
gasification plants in the US. A plant in St Lucie, Florida, has been
scaled back significantly, partly in response to environmental concerns,
and plans for a similar plant in Sacramento, California, have been
delayed indefinitely.

Another question mark over the green credentials of waste
gasification concerns just how efficient these plants are at producing
energy and minimising greenhouse gas emissions compared with other
methods of waste disposal. A recent study by the Tellus Institute, an
independent think tank based in Boston, compared gasification with
landfill sites where methane is captured to be burned for energy. It
concluded that while gasification produces six times as much energy per
tonne of waste as landfill sites, landfills with methane recapture
systems save two-and-a-half times as much CO2 equivalent as the
combination of gasification and syngas burning. The Tellus report also
found that the energy saved by recycling a given amount of waste is 3.4
times the energy that can be produced through gasifying it.

Some are opposed to gasifiers on principle. They say their very
existence discourages efforts to tackle the garbage crisis at its
source. "Once you build a gasifier, you have to feed it," says Tangri.
"It creates a financial disincentive to do waste reduction and
recycling."

Ultimately, it may be some time before we realise the full effects,
for good or bad, of zapping our rubbish. Few long-term independent
studies have been carried out into emission levels, dioxin contaminants
and the potential for toxins to leach out from waste ash. Nor is it
clear how much energy can be created by gasifying various types of
waste, or how reliable energy generation can be, given variations in the
waste stream from day to day and in different parts of the world. So
far, though, the indications are that gasification is neither the
panacea for our waste and energy woes that some are claiming it to be,
nor an environmental catastrophe waiting to happen.

For Kevin Whiting of Juniper, a British waste-processing consultancy
based near Dursley in Gloucestershire, the way forward may be on some
kind of middle ground. "If there is a market for recyclables, we should
recycle as much as is practicable and not take resources from our
great-grandchildren," he says. "But if waste can't be recycled, it has
an energy value. And the more energy you can generate [from it], the
better."