Plastics can be made from just about anything that has a large amount of carbon. Oil and natural gas have been the carbon source of choice for the past 100 years, although occasionally some other feedstock sources are used, such as salt brine for polyvinyl chloride (PVC).
In a survey Design News conducted earlier this year, design engineers said they are concerned about the future of oil as a feedstock for plastics because of its employment as a political weapon since the Arab Oil Embargo in 1974. Its volatile price is also an issue. And, more recently, climate change has also been a reason to deemphasize use of oil.
Some smart companies -- such as DuPont, Tate & Lyle, and Archer-Daniels-Midland -- saw an opportunity and invested heavily in new plants to produce plastics from renewable resources, that is, crops. The first big projects focused on corn in the US and sugar cane in South America.
This was a good idea because plants sequester carbon dioxide while they're growing; they can be replaced quickly (usually annually); and they are homegrown.
But use of food crops to make plastics is not the ideal solution to the problem. Even if those croplands are purpose-built to make a renewable feedstock for plastics, problems persist. For example, are any woodlands being removed to plant these crops? If so, then the carbon footprint argument is diminished. More importantly: Why are we using corn, sugar, soybeans, and other plants to make plastics (or fuel) when people are starving in the US, let alone India or Somalia?
Enter waste vegetation.
This comes to mind because of an interesting article in the current issue of the Scientific American. Carrie Madren writes: "As a single plant, cogongrass is unassuming, even bucolic. But in dense stands, it is a powerful vegetative force that alters forests and forges monocultures."
Ever heard of "cogongrass" before? Not me. But if you live in Alabama, Mississippi, Georgia, or Florida, you are becoming increasingly aware of this vegetative scourge. According to Cogoongrass.org, the weed has spread from Texas to South Carolina. And it may soon be coming to a meadow near you. It grows in a thick thatch, smothering the beautiful native plants of the South. It has a high ignition rate, creating a threat to Southern pine stands. And it's spreading faster than a Casey Anthony Tweet.
Ms. Madren writes that the State of Alabama has even established a "Cogongrass Control Center" to prevent a projected $7.5 million annual devastation of commercial timber. Even American Reinvestment and Recovery Act money is being sprayed on the scourge in an effort to dampen growth. Nothing really seems to stop this menace.
How's this for a no-brainer: Use cogongrass (Imperata cylindrica, by the way) to make plastics. OK, so maybe it's a little costly to harvest, bale, and ship this stuff to a bioreactor. But a total lifecycle analysis needs to consider moneys being spent to tame the scourge, as well as savings in firefighting costs and preserved timber. Plus, of course the intangibles, like maintaining native flora and fauna.
We don't need any federal commissions to investigate this. We don't need any Congressmen bloviating on CNN. We just need some brainy scientists from a company like DuPont to go down there, look around, and tell us what they think.
Ms. Madren's article is not posted on the Scientific American Website (yes, you actually have to buy a print copy of the magazine), but a very interesting source of information on cogongrass has been posted by Auburn University. It's titled: "Wanted Dead, Not Alive: Cogongass."
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