Bioplastics Boom
$this->bbcode_second_pass_quote('', 'A')lthough the plastics industry has depended predominantly on petrochemicals for feedstocks throughout most of its history, some early plastics were plant based. Parkesine, the first human-made polymer, was created by inventor Alexander Parkes in 1856 out of chloroform and castor oil. Henry Ford unveiled the now-legendary "soybean car," with soy-based plastic body panels, in 1941. Now, as the price of petroleum rises and concern mounts about the environmental effects of petrochemicals, the plastics industry is racing to create renewable polymers from bio-based sources.
To make the biopolymer, Braskem converts sugarcane-sourced ethanol into ethylene by a process called ethanol dehydration. This transfers 99 percent of the carbon in ethanol into ethylene, says Antonio Morschbacker, Manager of Technology for Green Polymers at Braskem. The main byproduct is water, which, when purified of contaminants (mainly ether and nonreacted ethanol), can be recycled. The ethylene is then polymerized. It would be impossible to tell Braskem's plastic from petro-polyethylene if not for a single difference: It contains trace amounts of the isotope carbon-14. Using the same process employed in radiocarbon dating, chemists can measure the amount of carbon-14 in plastic and use it to determine the percentage of biopolymer it contains. The ability to certify its bioplastic using ASTM International standards (in this case, ASTM D6866) gives Braskem a marketing edge. The material will be used in packaging for food and cosmetics, but Morschbacker expects the major application will be in the automotive industry, where the bioplastic will be used in injection and blow molding. Henry Ford's soybean car may well return, albeit in a slicker, smoother reincarnation.
"You can't argue with the fact that a bio-based plastic offers better possibilities for end-of-life treatment," says Williams. The carbon released from these plastics represents no net addition to the atmosphere, whereas the production and incineration of petrochemical plastics boosts CO2 levels. Because Braskem's polyethylene is identical to fossil-based plastics, it can be recycled along with them, making it possible to integrate the new material into established recycling systems. This trait also makes it easier for producers to adopt the new polymer. According to Morschbacker, it can be processed using the same equipment and settings that companies use for petroleum-based polyethylene. The machinery will never know the difference. Incineration at high temperatures (900 degrees Celsius) also shows promise. And though the technology is still new and the number of plants small, some companies are also using catalysts or microwaves to convert the polymers into gasoline or diesel. This could be good news for the biofuels sector as well: Recycling bioplastics into fuel could allay concerns about the use of food crops in biofuels production.







