April 24, 2007 4:00 AM PDT

Plastic goods for your compost heap

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There are already biodegradable packaging products created with polyactic acid (PLA), also typically made from corn starch.

Metabolix executives said PLA does not stand up as well to heat as Mirel and can be composted only in industrial composting facilities.

Mirel plastic can biodegrade in soil or any type of compost pile. It will also break down in septic systems and waste treatment facilities or in wetlands and marine environments.

"The key thing with Mirel is that it opens up a range of options for the end-of-life fate," Barber said. "Now plastics last hundreds or thousands of years."

On the other hand, PLA is clearer than Mirel, so most likely it will be used to package products that will be chilled, like produce or sandwiches, Barber said.

Another company called Cereplast is also making biodegradeable goods, such as food packaging and utensils, from corn starch.

In contrast to Metablox, Cereplast said that with rising petroleum prices, its corn-based products will be the same price or cheaper than traditional plastics.

ADM chose to partner with Metabolix because its patented technology makes it a leader in the field, said Terry Stoa, vice president of technology assessment at ADM.

He said that the production plant, now under construction, will be capable of making 110 million pounds of Mirel per year.

Although the company is betting that consumers will be willing to pay more for Mirel as a green product, company executives concede there isn't a great awareness of how plastics are produced today.

A study commissioned by Telles found that 72 percent of the American public does not know that conventional plastic is made from petroleum.

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Is It Really Better?
OK, so traditional plastic is made from petroleum and it doesn't degrade (or do so very slowly). Traditional plastic can be recycled.

The questions I have are:

1. Is there any side effect on the environment from the modified corn starch when it degrades? Just because they call it "green" and make it from plant materials doesn't make it good for the environment. After all, petroleum comes from plants, too.

2. What is the total cost? There's energy expended to retrieve and refine petroleum, and energy is needed to produce and recycle traditional plastics. Likewise, there are effects from growing, harvesting, and refining corn plus those of creating Mirel. On balance, which is better?

3. How practical is Mirel? For example, under what conditions does Mirel degrade? Will a water spill cause a leak? What if it's left outside? How long before the container is useless? Can Mirel be used only for dry goods? If it's used for frozen foods, will melting ice/frost be a problem? Can it be used for medical supplies?

I'm sure there are other questions, but these are the sorts of things I'd like c|net to share with us. Most of these green stories simply convey ideal notions rather than asking tough questions and comparing the whole picture. I'd like to see more in the future.
Posted by c|net Reader (856 comments )
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"(or do so very slowly)" should have been "(or does so very slowly)" of course.
Posted by c|net Reader (856 comments )
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Some answers from reporter
1. As I understand this, it's made from plain old corn starch so there won't be any unknown environmental effects as products degrade.

2. I don't have a detailed analysis of the two separate processes of making plastics from oil and plastics from petroleum, but on balance, it appears that plant-based plastics take less energy over its lifecycle. Just looking at disposal, a plant plastic will degrade with no effort (and creates fertilizer), whereas recycling takes additional energy. And, as you point out, extracting and refining oil and creating plastics is very energy-intensive.

There are other potential benefits as well, when you consider that a lot of plastic is not recycled and simply remains an environmental pollutant for a long time.

3. Mirel can be used for liquid containers, even boiling water and won't degrade. The process takes months, depending on thickness, but decomposition will only happen if the plastic is buried in soil or in bodies of water where microbes can eat away at it.

Finally, I think you raise a good point about our green tech coverage overall. Many products aim to be environmentally friendly but nearly everything will have some sort of drawback or limitation. We can try to lay out the pros and cons and introduce more analysis.
Posted by mlamonica (330 comments )
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