Polyethylene Made From Ethanol 9 Times More Efficient To Source From Sugar Cane, Over Corn
TetraPak to use biopolymer caps and closures made from sugar cane derived ethanol. Image credit:Tetra Pak plans bioplastic trials in 2011, via PackagingNewsCoUK
A Brazilian plastic company Braskem SA reports that, using ethanol feedstock, their polyethylene process, scheduled to operate commercially in 2011, will make product with exactly the same characteristics as polyethylene derived from petroleum. Environmental- and cost-efficiency of the process hangs on feedstock choice. It will be "nine times as efficient to derive ethanol from sugarcane as from corn, and four-and-a-half times as efficient compared to ethanol derived from sugar beets." Even more strikingly, a spokesman for Braskem reported, manufacture of one pound of petroleum-based polyethylene "releases 2.5 kg of carbon dioxide to the atmosphere,...whereas the same amount of sugarcane-based PE captures that same amount of the gas."
Think of the political consequences if US polymer makers relied extensively on sugar cane feedstock for meeting US polyethylene demand: Florida and Louisiana would become the early Presidential primary states, Iowa would fade into obscurity, USDA sugar subsides would skyrocket, and seed companies would genetically modify sugar cane to grow in Maine (although with climate change that may not be needed).This is pretty much the sames story as fuel based ethanol, for which Brazil has demonstrated a much higher overall efficiency than US corn based ethanol processes.
Plastics Today has the full story on how sugar cane PE will be used in the new TetraPak design: Bioplastics: Tetra Pak tasks Braskem for bio-based HDPE
Braskem will begin supplying Tetra Pak with 5000 tonnes per year of "green" HDPE from 2011, which Tetra Pak says is a bit more than 5% of its annual HDPE requirement. Linda Bernier, director of corporate PR at Tetra Pak, told MPW that the company injection molds some of its closures but also buys them on the market, and has not yet decided who will process the Braskem HDPE. Braskem, South America's largest chemicals and plastics supplier, expects to bring its green polyethylene plant online late next year. Sugar cane is used to produce ethylene, which can then be converted into polyethylene.The important thought, here, is that if, in a half-century or so, biopolymers are to replace petro-polymers, that feedstock supply chains will mainly originate in tropical and subtropical areas - in continental USA, not so much. To make it a precept of US industrial policy that raw materials for a sustainable economy must come mainly from homeland is impractical.
Unless, of course, US companies can make ethanol from trees, in a manner that is cost competitive with Brazilian sugar cane, and government encourages making durable goods with ethanol instead of burning it as motor fuel. That has some resilience.