ÐÓ°ÉÔ­´´

Australians use the term ‘intractable wastes’ to describe their stockpile
of discarded organochlorines such as PCBs, hexachlorobenzene, dioxin and
pesticides. The term is seldom used outside Australia because other countries
destroy such hazardous waste in high temperature incinerators. But Australia
still does not have an incinerator: for nearly two decades, public protests
have defeated at least eight attempts by government authorities to build
one.

Despite continuing public opposition, environmentalists are now convinced
that the governments are determined to build the incinerator they have long
sought. The environmentalists point to the way funds for research into alternatives
have dried up and to the federal government’s appointment in April of an
independent panel to supervise the preparation of a study into the environmental
impact of an incinerator.

About 11 000 tonnes of intractable waste are stored in Australia, the
bulk of it in New South Wales. The solvents plant at the ICI Australia complex,
near Botany Bay in Sydney, produces about 80 per cent of the waste. The
plant’s 400 tonnes of hexachlorobenzene per year are a by-product of the
production of carbon tetrachloride and perchloroethylene. Imports of intractable
waste, such as used PCBs and left over pesticides, account for about 15
per cent of the stockpile.

Federal and state governments say the stockpile will not grow much more
because ICI plans to close its solvents plant next year as CFCs, for which
carbon tetrachloride is a feedstock, are phased out. (Production of perchloroethylene,
a chemical used for dry cleaning, will become uneconomic and also cease.)
They say they just want to build a small incinerator to get rid of the stockpile
once and for all within 10 years. Environmentalists fear that once incineration
of waste starts, it will not stop.

The stockpile is not large by world standards, amounting to one-eighth
of the hazardous waste incinerated every year in New Jersey. But the absence
of a high temperature incinerator in Australia has encouraged research into
alternative methods of waste disposal. ICI has been investigating alternatives
since the mid-1970s while the University of New South Wales and CSIRO, Australia’s
national research organisation, have run similar research programmes for
at least five years.

Environmentalists say that this research is now under threat: last year,
the federal government and the state governments of New South Wales and
Victoria (the only states still producing intractable waste) short listed
seven sites for an incinerator in New South Wales. The governments say it
is safer to destroy the stockpile as quickly as possible than to wait to
see if any of the emerging technologies prove commercially viable. The environmental
pressure group Greenpeace dismisses this argument: ‘If stored chemical wastes
are so dangerous, why are the governments not equally concerned about the
risks posed by chemicals being stored for use? There are far more of them
and they are just as dangerous.’

Greenpeace wants more time and money spent on alternatives to incineration,
which it says produces toxic emissions and residues. Greenpeace cites the
work of James Beattie, associate professor of chemistry at the University
of Sydney, who is using ruthenium as a catalyst to break down intractable
waste at low temperatures, typically less than 100 °C. In this method,
known as the Sydox process, the low temperature prevents dioxins from forming,
says Beattie. Instead, the products are nontoxic inorganic salts, such as
sodium chloride and sodium carbonate.

Ruthenium is a versatile catalytic oxidant of many organic compounds
and is already used in organic synthesis. Its use as a catalyst in the oxidation
of dioxins was first reported in 1981 by David Ayres, honorary senior research
fellow at Queen Mary College, London (Nature, vol 290, p 323).

While Beattie has been investigating the Sydox process with a laboratory
model, teams of chemical engineering students at the university have been
working out how to build a full-scale plant. But there are no funds available,
from government or industry, to develop their ideas further. Beattie blames
the federal and state governments’ commitment to build a high temperature
incinerator and legally force producers of organochlorine waste to use it:
‘Clearly there is now no incentive for Australian industry to develop alternatives.’

He argues that even if the Sydox process proves not to be an appropriate
alternative to incineration, his work has shown that organochlorine waste
is not intractable. Within five years, he says, technologists could develop
methods for breaking it down in moderate conditions rather than ‘using the
sledge hammer approach of a high temperature incinerator’.

CSIRO is developing another alternative, plasma arc technology, in which
an electric current ionises an inert gas, such as argon, in a furnace to
temperatures of between 10 000 °C and 20 000 °C. This plasma ionises
wastes injected into it, breaking them down in the absence of oxygen, which
reduces the chances of dioxins forming, says Rama Ramakrishnan, the project
manager. CSIRO is currently negotiating with Nufarm, a chemicals company
based in Melbourne, to design and build the world’s first commercial waste
disposal system based on plasma arc technology. Ramakrishnan says the system,
which would have to consume less than 3 tonnes of toxic waste a day, could
be working for Nufarm by the end of the year.

Searching for foreign aid

CSIRO now wants funds to develop the process for the commercial destruction
of larger quantities of concentrated organochlorine waste. More research
is also needed on what to do with the hot gases emitted from the furnace.
They could be used as feedstock to produce chemicals, such as hydrochloric
acid, or as fuel to generate electricity. The organisation’s search for
A $5 million ( £2.3 million) over three years has attracted inquiries
from the US and Europe but little interest in Australia.

Meanwhile, at the University of New South Wales, researchers are investigating
supercritical fluid technology as an alternative to the incineration of
intractable waste. Supercritical fluids are created when gases are compressed
beyond the critical point at which they would normally become liquids. In
this state, they exhibit properties of both gases and liquids. Their advantage
in the disposal of intractable waste is that they can dissolve organic compounds.
Neil Foster, the university’s associate professor of chemical engineering,
is developing a process that uses supercritical water, heated to between
450 °C and 550 °C and confined at a pressure of 220 atmospheres.
Adding oxygen to the mixture converts the waste into acids, such as hydrochloric
acid, which can be neutralised with caustic soda. The inorganic salts formed
precipitate out of the supercritical fluid and the gaseous products of the
reaction, mainly carbon dioxide and steam, are emitted into the atmosphere.
The steam can be collected and recycled.

Modar Technology, a consortium of engineering firms including AVB of
Switzerland and Lummus and Crest of the US, holds the patent for the process.
Modar claims its technology is as effective as incineration, being capable
of destroying Australia’s stockpile of intractable waste with an efficiency
of 99.9999 per cent. Traces of toxic chemicals could be emitted, though
Foster argues that dioxins are less likely to form at temperatures below
550 °C than they are in incinerators operating at temperatures above
1000 °C.

Western military authorities are investigating supercritical fluid technology
as a method of disposing of chemical weapons, says Foster. This follows
increasing public pressure in the US to find alternative ways of destroying
the weapons and opposition from Pacific nations to plans by the US to incinerate
its chemical arsenal on Johnston Atoll (New ÐÓ°ÉÔ­´´, This Week, 4 August
1990). Foster attended a NATO workshop in Leeds last year at which international
experts were asked to come up with ways of developing the technology quickly.

Despite such initiatives, the Waste Management Authority of New South
Wales, the organisation responsible for disposing of the state’s stockpile
of intractable waste, refuses to support the development of alternatives
to incineration. Early last year it announced: ‘It would not be appropriate
for Australia to become a ‘guinea pig’ for unproven technology.’ Ross Thomas,
the authority’s project manager for the planned high temperature incinerator,
says it would take between 10 and 20 years to develop alternative technologies
to treat intractable wastes on a large scale. He adds that, even then, such
technologies would not be able to deal with the wide range of wastes that
could be incinerated. Promoters of the alternative technologies argue that
their processes could be used with others tailored to destroy specific types
of waste.

‘Intractable waste’ traditionally refers to a narrow range of organochlorine
waste. In 1988 however the government-appointed Joint Task Force on Intractable
Waste proposed that the incinerator should destroy other hazardous chemical
wastes dumped in landfills. These include paint and resin residues, organic
solvents, oily waste and non-organochlorine pesticides, produced at the
estimated rate of 12 000 tonnes per year in New South Wales. Broadening
the mix would also make it easier to incinerate the waste – intractable
waste alone does not burn very well.

Too dangerous to burn

The taskforce decided that a rotary kiln incinerator could do the job
but in 1989 ICI Australia questioned this decision. The company said that
the 9000 tonnes of intractable waste at its Botany Bay plant have ‘unusual
physical and chemical properties and could not be safely and innocuously
destroyed in any known conventional rotary kiln’. The waste, mainly hexachlorobenzene,
contains up to 80 per cent of chlorine by weight, well above the 10 per
cent limit recommended by incinerator manufacturers to reduce the risk of
hazardous dioxins and furans being formed. Instead of building one general-purpose
kiln, ICI proposed that the Waste Management Authority should build one
for intractable waste and another for other wastes.

More recently, the authority has added CFCs and halons to the list of
wastes to be incinerated, estimating that around 80 000 tonnes of these
ozone-depleting chemicals will be discarded over the next 10 years. The
decision has raised new doubts among environmentalists about the viability
of an incinerator; they point to the fierce corrosiveness of the combustion
products. As halons and CFCs break down, they produce either the halogen
acids (hydrogen chloride, hydrogen fluoride and hydrogen bromide) or the
free halogen molecules (chlorine, fluorine and bromine). These products
are so corrosive that a resistant lining for the incinerator is essential
to protect the equipment.

The products can do even more damage if they escape into the atmosphere.
Some scientists regard fluorides as the most phytotoxic of the common pollutants.
Low concentrations can injure plants or accumulate and enter the food chain,
causing disease in herbivores (International Journal of Environmental and
Analytical Chemistry, vol 39, p 223). Other potential emissions include
phosgene (a nerve gas), dioxins and furans.

And the Australian proposal for a single incinerator differs from normal
practice elsewhere in the world. Incinerators designed for destroying CFCs
operate at the CFC production plants of Du Pont and Pennwalt in the US,
of ICI in Britain and of Hoechst in Germany. Where conventional toxic waste
incinerators are used, the proportion of CFCs is limited. In the US, some
incinerators can burn no more than 100 parts of CFCs per million; none can
burn waste containing more than 5 per cent CFCs. In Australia, the Waste
Management Authority’s plans to incinerate a large proportion of CFCs and
halons with other toxic waste represent a major departure from such guidelines.
This is ironic when contrasted with the authority’s refusal to let Australia
be a ‘guinea pig’ for the development of alternative technologies.

One of the problems of burning CFCs or halons is the difficulty of controlling
the formation of products of incomplete combustion, or PICs, which are often
toxic. Little is known about these PICs because until recently few people
considered incinerating the chemicals. In the US in 1989, the Environmental
Protection Agency (EPA) estimated that it could take five years to fill
the knowledge gaps.

The task force has admitted that CFCs would not need to be incinerated;
it said that recycling and substitution would prevent waste from stockpiling.
The consumption of CFCs has already decreased significantly. In 1990, Australia
produced and imported about 8000 tonnes of CFCs, but this was about half
the amount it needed in 1986.

Compromising commitments

The Waste Management Authority’s decision to plan for the incineration
of 80 000 tonnes of CFCs over the next 10 years comes as a surprise to Graham
Bailey, manager of Robinair Australia, which recycles the chemicals. He
doubts that there will ever be large stockpiles of CFCs while companies
can make money from recycling them.

The decision to continue producing and importing CFCs while making provisions
to destroy them within 10 years also throws doubt on the Australian government’s
commitment to recycling and minimising waste. And yet the Montreal Protocol,
the international agreement to end the use of chemicals that damage the
ozone layer, encourages such an attitude because it allows countries to
increase their production of CFCs and halons in line with the volume destroyed.
Australian manufacturers can produce more CFCs as long as they are also
destroying them.

Manufacturers cannot claim that recycling is uneconomic. In 1989, the
EPA reported that recycling CFCs cost about the same as destroying them,
so recycling was more economic than destroying CFCs and paying for replacements.
In Australia, however, the government’s plan to cover the costs of destruction
makes recycling uneconomical for manufacturers.

Supporters of alternative methods of disposing of intractable waste
fear that if the federal and state governments decide to spend up to A $50
million on an incinerator it will want the volume of wastes to be large
enough to ensure that the equipment remains economically viable. Beattie
suspects this is the reason for the decision to burn CFCs in the planned
incinerator. An incinerator will also be more viable if those volumes can
be maintained over its lifetime: this will reduce the incentive for recycling.

So far the absence of a high temperature incinerator in Australia has
encouraged recycling and minimising waste. Between 1977 and 1988, ICI developed
recycling methods that reduced the waste from its ethylene dichloride plant
by 3000 tonnes a year. The plant produces feedstocks for the production
of polyvinylchloride, or PVC. In other countries, waste from similar plants
was incinerated.

If the federal and state governments fail to find a site for Australia’s
first incinerator it may be a blessing in disguise. Without an incinerator,
both government and industry will be encouraged to minimise the waste they
produce. They will also be more likely to support the development of safer
and more environmentally sound ways of disposing of the stockpile of intractable
wastes.

Sharon Beder is a professional engineer who coordinates environmental
education at the University of Sydney.

* * *

The high temperature route to disposing of hazardous waste

A rotary kiln is a cylinder that rotates slowly at a slight angle. Wastes
continuously fed in at one end gravitate to the other. On the way, they
mix and are exposed to flames at temperatures of around 1100 °C, which
convert the wastes into a solid residue and hot gases.

The solid residue can be up to 29 per cent of the original volumes depending
on the content of the waste stream. The Waste Management Authority of Australia
proposes to bury it on site. The residue, often referred to as the ash,
may contain traces of toxic material that can leak into nearby waterways.

The government of New South Wales rejected the first site proposed by
the Joint Task Force on Intractable Waste. It ruled that the site, at Corowa
on the border between New South Wales and Victoria, was too close to the
Murray River – one of Austalia’s major waterways and a source of irrigation
and drinking water for three states.

The hot gases pass from the rotary kiln into a second chamber, or after-burner,
where they are heated at 1200 °C for two seconds. During this stage
any remaining waste molecules are supposed to break down into harmless chemical
compounds. The by-products are then rapidly cooled to ensure they do not
form more harmful chemicals. The gases are then ‘scrubbed’ with high velocity
water to remove acid and remaining ash particles. A third chamber may be
added to clean the gas further.

Emissions are toxic if the waste is not burnt at a uniformly high temperature.
For example, material in the middle of solid wastes may be insulated from
the heat and oxygen. To reduce the chances of this happening, modern incinerators
are designed to liquefy the solid waste and to maintain a uniform high temperature.
The incinerators’ manufacturers claim a destruction and removal efficiency
(DRE) of 99.9999 per cent. This is a way of measuring how much of the original
waste remains in the gases emitted from the furnace into the atmosphere.
For example, for every tonne of PCBs incinerated, the manufacturers claim
that no more than 0.0001 per cent, or 1 gram, will escape.

What the DRE does not measure is the extent to which the waste is only
partially broken down nor the extent to which atoms recombine to form new
hazardous chemicals. Nor does it indicate how much waste or products of
incomplete combustion remain in the residue or scrubber water.

The Waste Management Authority of New South Wales has told local residents
near the short-listed sites that the proposed incinerator will meet the
toughest environmental standards in the world. It says that annual emissions
of dioxins will be less than those from an average bush fire, some-thing
many of them are all too familiar with. Yet the residents wonder why, if
the incinerator is so safe, it cannot be sited in Sydney where most of the
intractable waste is stored. The short-listed sites are all in rural areas,
hundreds of kilo-metres from Sydney.

Environmentalists are also concerned about leaks that result from accidents
and from fugitive emissions, which include releases from valves, minor ruptures
and incidental spills during transfer of the waste from one container to
another. In 1985, the Science Advisory Board to the US Environmental Protection
Agency acknowledged that ‘fugitive emissions and accidental spills may release
as much or more toxic materials to the environment than the direct emissions
from incomplete waste incineration’. Such releases are still a problem;
research into improvements in incineration have concentrated on achieving
uniform temperatures and methods of treating toxic stack gases.

The management and operation of an incinerator can be more important
to public and environmental health than the design of the technology and
how efficiently that technology works under trial conditions.