editor's desk  |   links  |   green market  |   comment  |   earth maps   |   press  |   advertise  |   team  |   about  |   news room   |   greener advice

Tuesday, March 27, 2007

Plastic that degrades in seawater?

A new type of environmentally friendly plastic that degrades in seawater may make it safe and practical to toss plastic waste overboard, freeing valuable storage space for military, merchant and cruise ships generating large volumes of plastic waste that must be stored onboard until they reach port.

Large volumes of plastic waste generated aboard military, merchant and cruise ships must be stored onboard, often for prolonged periods, until they make port. A new type of environmentally friendly plastic that degrades in seawater may make it safe and practical to toss plastic waste overboard.

Editor's note: Considering recent bioengineering research including limited success with interspecies cloning and the discovery that a third natural form of carbon called nanotubes can be formed into structures called "buckyballs"(nanotubes of carbon, which form tetrahedral nanospheres can become self replicating) we couldn’t help but recall this fascinating video clip from Theo Jansen, sculptor and design/engineer who hopes to populate a world with ambulatory, plastic, wind driven creatures he calls “Strandbeests”.

According to scientists at The University of Southern Mississippi (USM), the biodegradable plastics could replace conventional plastics used to make stretch wrap for large cargo items, food containers, eating utensils and other plastics used at sea, the researchers say. The development was described today at the 233rd national meeting of the American Chemical Society.

“There are many groups working on biodegradable plastics, but we’re one of a few working on plastics that degrade in seawater,” says study leader Robson F. Storey, Ph.D., a professor of Polymer Science and Engineering at USM, located in Hattiesburg, Miss. “We’re moving toward making plastics more sustainable, especially those that are used at sea.”

Conventional plastics can take years to break down and may result in byproducts that are harmful to the environment and toxic to marine organisms, conditions that make their disposal at sea unacceptable. The new plastics are capable of degrading in as few as 20 days and result in natural byproducts that are nontoxic.

The new plastics are made of polyurethane that has been modified by the incorporation of PLGA [poly (D,L-lactide-co-glycolide)], a known degradable polymer used in surgical sutures and controlled drug-delivery applications. Through variations in the chemical composition of the plastic, the researchers have achieved a wide range of mechanical properties ranging from soft, rubber-like plastics to hard, rigid structures, depending on their intended use.

When exposed to seawater, the plastics degrade via hydrolysis into nontoxic products, according to the scientists. Depending on the composition of the plastics, these compounds may include water, carbon dioxide, lactic acid, glycolic acid, succinic acid, caproic acid and L-lysine, all of which can be found in nature, they add.

Because the new plastics are denser than saltwater, they have a tendency to sink instead of float, Storey says. That feature also could prevent them from washing up on shore and polluting beaches, he notes.

The plastics are not quite ready for commercialization. More studies are needed to optimize the plastics for various environmental conditions they might encounter, including changes in temperature, humidity and seawater composition, Storey says. There also are legal hurdles to overcome, since international maritime law currently forbids disposal of plastics at sea.

Greener News Room

Editor's note: Although intriguing and certainly not without practical applications, does the effort to conserve space aboard cruise ships really qualify as a "sustainable" use of limited resources? Rather than encourage research into perfecting a means for the maritime industry to return to "dumping" their garbage at sea perhaps we could enlist resarchers at MIT to construct a better trash compactor.

At the very least cruise lines might consider reusable utensils, plates and liquid containers.



Top of Page

1:47 PM