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New Technology Helps Alcoa Cut Greenhouse
Gases
By EDMUND F. SCHERR
U.S. aluminum giant cut its greenhouse gas emissions 25 percent in
three years.
Alcoa, a world leader in aluminum manufacturing, is also leading private
sector efforts to reduce greenhouse gas emissions and use renewable energy
resources. With operations in 44 countries, the U.S.-based company's
policies and innovations have a global effect.
Alcoa was named by the World Economic Forum in Davos, Switzerland, as one
of the top companies in sustainable use of natural resources in early
2007. Alcoa is also a founding member of the U.S. Climate Action
Partnership, a collection of businesses and environmental groups lobbying
the U.S. government for legislation limiting greenhouse gas emissions.
In 2000, the company laid out its goals for reducing its impact on the
global environment through innovation and new technology. The goals
included deep reductions in greenhouse gas emissions and waste product
discharges. Alcoa reached its goal of reducing greenhouse gas emissions by
25 percent (from 1990 levels) in 2003, seven years ahead of schedule, even
though aluminum production increased during that period.
The company believes that the aluminum industry can be "greenhouse gas
neutral" by 2020.
Renewable energy is a key to Alcoa's efforts to reduce its environmental
impact. It has used hydroelectric power as a major energy source for its
smelting operations around the world since 1916 and is now evaluating the
feasibility of building the world's first geothermal-powered aluminum
production plant in Iceland.
In May 2007, Alcoa launched "carbon capture" technology at its Kwinana
alumina refinery in western Australia. The process for capturing carbon
dioxide mixes bauxite residue, a byproduct of the aluminum-making process,
with carbon dioxide. This locks up large amounts of the greenhouse gas
that otherwise would be released into the atmosphere.
By mixing carbon dioxide into the bauxite residue, the compound's pH level
(a measure of acidity and alkalinity) is reduced to levels normally found
in alkaline soil. This new mixture can be used as road foundation,
building material or an additive to improve soil. This technology, which
the company plans to share with the entire aluminum industry, will be used
in Alcoa's alumina refineries worldwide. Alumina, also known as aluminum
oxide, is the main component of bauxite, the principal ore used in
aluminum production.
Alcoa is also researching innovative new "inert anode" technology to
reduce greenhouse gas emissions even further. In the final stage of
smelting, aluminum oxide, processed from bauxite ore, is placed in an
electrolytic cell. A carbon rod, called an anode, is fed into the cell and
charged with an electric current, converting the aluminum oxide into
carbon monoxide, carbon dioxide and aluminum. The aluminum sinks to the
bottom of the tank, where it is collected for additional processing, while
the greenhouse gases escape through the opening where the anode is
inserted. Alcoa is working to develop technology that would allow it to
replace carbon anodes with ones that would not react with the oxygen
released in the electrolytic process to create greenhouse gases. The only
byproduct of the "inert anode" process would be oxygen.
An industry study, the "Inert Anode Roadmap," says worldwide use of inert
anodes could reduce greenhouse gas emissions by nearly 40 million metric
tons. It also could reduce the amount of electricity needed to smelt
aluminum oxide into aluminum by 25 percent.
Alcoa is working to reduce hazardous waste from its operations as well.
The spent pot lining (SPL) that remains after the smelting process
contains significant amounts of absorbed fluorides and some cyanide. In
the past, this waste has been deposited in landfills.
However, the new Alcoa Portland SPL process converts SPL to aluminum
fluoride (an important additive in aluminum production) and a harmless
granulated glassy material called synthetic sand. This synthetic sand can
be used to make roads and concrete.
Edmund F. Scherr is a USINFO staff writer.
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