PLASTIC FROM POLLUTION: Researchers have demonstrated on a small scale that with sufficient energy and pressure they can turn the greenhouse gas carbon dioxide into useful plastic. Image: ©VASILIKI VARVAKI/ISTOCKPHOTO
Researchers announced this week that they are perfecting a procedure designed to turn pollution into a type of plastic used to make everything from DVDs to eyeglass lenses. The effort is being touted as a way to capture and use climate change–causing carbon dioxide (CO2) emissions from coal-fired power plants and other sources instead of releasing it into the atmosphere or burying it underground.
"One is producing a material from CO2 instead of just discarding it," chemist Thomas Müller of the Center for Catalysis Research at RWTH Aachen University in Germany said yesterday at a press conference at the semiannual meeting of the American Chemical Society in New Orleans. "It can be a contribution to solving the CO2 problem."
Plastics such as polycarbonates are long chains of carbon atoms bonded to such elements as oxygen. The tough plastic is currently constructed from the long carbon chains, or polymers, made from fossil fuels. But Müller says that chemists could convert the nearly 10 billion metric tons of carbon dioxide emitted by coal-fired power plants—if captured—into such plastics by applying pressure and using energy to trigger the necessary chemical reaction.
Muller says his team used an undisclosed catalyst to transform captured CO2 into the polymers such as epoxide and dimethyl carbonate needed to make a polycarbonate. Chemist Toshiyasu Sakakura of the National Institute of Advanced Industrial Science and Technology in Tsukuba, Japan, reported that his team achieved similar results by combining captured CO2 with methanol as well as a compound made of the catalyst phosphine on silica (more commonly known as sand).
Much to Sakakura's surprise, using elemental sand to support the catalyst dramatically boosted its effect. "Surprisingly, in that case, one plus one is not two," Sakakura said at the press conference. "One plus one equals 100." The chemists are not sure why silica, which is not a catalyst, appeared to help produce more polymers than expected.
Sakakura said that the only waste product of these chemical reactions was water. But the processes do have a downside: coaxing the carbon dioxide molecules to form longer chains requires high temperatures and great pressure—and, so, extra energy.
Because that additional energy would likely come from burning fossil fuels, Müller says, the "overall process of converting CO2 to polymers at present would produce more CO2." That means the process would only pay off environmentally if clean alternative energy sources such as solar or wind power are used to fuel it. "We need alternative sources for energy," he says. In that event, everything from soda bottles to police riot shields might one day help sequester some of the most common greenhouse gas currently warming the planet.