11(P)/S/O
CENTRAL CHRONICLE, BHOPAL, 28 JAN 08
Eagle's Eye:
Plastics from Carbon Dioxide
Need is to reduce carbon dioxide emissions or to make use of the emitted carbon dioxide
as a useful product and also to make biodegradable plastics- Dr SS Verma
Today, a purely scientific transformation focused on toxic into green is catching up.
Chemistry is the science of making new man-made types of matter and for that
understanding of chemical reactions well supported by suitable catalysts is required. By
controlling chemical reactions one type of matter in conjunction with other type of matter
may lead a way to tackle some unwanted matter outcomes of human activity to useful
conversion of matter for mankind. At one hand, we are aware of growing menace of
carbon dioxide as a result of so called developed human civilization and on the other we
all know the emergence of plastic as a necessary evil. Need is to reduce carbon dioxide
emissions or to make use of the emitted carbon dioxide as a useful product and also to
make biodegradable plastics. Both these desired goals are near to fulfillment
simultaneously with the development of called carbon-dioxide plastics which will help in
utilizing the undesired carbon dioxide emissions in making biodegradable plastics.
Researchers are working to transmute the way we do chemistry itself. In the lab and on
the shop floor, zero-emission green chemistry is beginning to replace traditional practices
that rely on non-renewable petrochemicals and toxic organic solvents. Moreover, many
of these new practices are often vastly more efficient than the ones they are replacing.
Research and development to reduce emission of CO2, green house effect gas, has
recently been progressing to eliminate global warming phenomena and material synthesis
processes with lower environmental impact have been noticed to realize the sustainable
society. Experimental methods are being developed for the application of phase reaction
field composed of supercritical CO2 and ionic liquids to organo-synthesis of plastic raw
materials, such as dimethylcarbonate useful as raw material of polycarbonate, along with
synthesis results.
Researchers first found a way to make biodegradable plastics called aliphatic
polycarbonates from carbon dioxide in 1969. They used carbon dioxide and a class of
compounds called epoxides. But the process requires expensive catalysts, high
temperatures, and pressure. The plastic costs more than $100 a pound and is used only in
specialty products such as biomedical and electronic devices. The Cornell University
(USA) spinoff's technology centers on a catalyst that converts carbon dioxide into a
polymer that could be used to make everyday items such as packaging, cups, and forks.
The plastic, which was originally created by Cornell chemist Geoffrey Coates, is also
safe and strong enough to be used in medical implants and devices.
Professor C.J. Li is also working on a process that will enable us to use waste CO2 to
create polymer plastics. Dr Li's (McGill Univ. Canada) important discovery is a new
process that he predicts will make it possible to create polymer plastics from CO2. This
has multiple commercial and environmental benefits, not the least of which is the
elimination of petrochemicals and toxic solvents from the plastics-making process. It also
has huge implications for environmental global warming. Instead of burying waste CO2
to reduce its greenhouse effects it's far more efficient to turn it into something useful.
This new plastic has extremely good properties, and another big advantage, it's
biodegradable. If people throw it out, it decomposes and becomes CO2 again.
Affordable, biodegradable plastics made from carbon dioxide are moving closer to
market. A company, Novomer, based in Ithaca, NY (USA) is working on
commercializing a process to convert carbon dioxide into different forms of
biodegradable polymers, including a honeylike liquid and a powder. The plastic is being
made on a pilot scale, and Novomer declines to give details of its commercial-scale
manufacturing plans. At present while it is hard to predict the product's final cost, it is
expected to be cost competitive with traditional petroleum-based plastics as carbon
dioxide is a cheap feedstock.
Novomer uses the same raw materials--carbon dioxide and epoxides--but its product is
distinguished by a metallic catalyst developed by Coates. The zinc-based catalyst works
at room temperature and low pressure, and it's faster. The polymer has different
properties--it can be hard, soft, transparent, or opaque--based on the type of epoxide used.
It is also biodegradable, since the carbon-oxygen bonds in Novomer's polymer are
relatively easy for bacteria to break down. Though the company has not tested the
degradability of the polymer, but aliphatic polycarbonates in general have been shown to
degrade in six months in composts under ideal conditions.
Though, in terms of biodegradability, the carbon-dioxide plastic will have to compete
with several other plant-based plastics now on the market but even the use of carbon
dioxide and carbon monoxide as inexpensive feedstocks in plastic making, instead of the
corn-based feedstocks used by other biodegradable plastics, means that the carbondioxide plastic formation won't compete with food production.
Dept of Physics, SLIET, Longowal