How long does it take for plastics to biodegrade?
"Drop a ketchup bottle on the floor, and you'll be thankful for polyethylene terephthalate, or PET, the nearly indestructible plastic used to make most containers and bottles. Drop the same bottle into a landfill, however, and you might have second thoughts. Why? Because petroleum-based plastics like PET don't decompose the same way organic material does. Wood, grass and food scraps undergo a process known as biodegradation when they're buried, which is a fancy way of saying they're transformed by bacteria in the soil into other useful compounds. But bacteria turn up their noses at plastic. Load their dinner plates with some plastic bags and bottles, and the one-celled gluttons will skip the meal entirely.
Based
on this logic, it's safe to argue that plastic will never biodegrade.
Of course, that's not the end of the story. Daniel Burd, a student at
Waterloo Collegiate Institute, recently demonstrated that certain types
of bacteria can break down plastic. His research earned the top prize at
the Canada-wide Science Fair, earning him $10,000 cash and a $20,000
scholarship [source: Kawawada].
Until other researchers can replicate Burd's experiment and waste treatment plants can implement any new processes, the only real way to break down plastic is through photodegradation. This kind of decomposition requires sunlight, not bacteria. When UV rays strike plastic, they break the bonds holding the long molecular chain together. Over time, this can turn a big piece of plastic into lots of little pieces.
Of course, plastic buried in a landfill rarely sees the light of day. But in the ocean, which is where a lot of discarded grocery bags, soft drink bottles and six-pack rings end up, plastic is bathed in as much light as water. In 2009, researchers from Nihon University in Chiba, Japan, found that plastic in warm ocean water can degrade in as little as a year. This doesn't sound so bad until you realize those small bits of plastic are toxic chemicals such as bisphenol A (BPA) and PS oligomer. These end up in the guts of animals or wash up on shorelines, where humans are most likely to come into direct contact with the toxins.
One solution to this environmental disaster is biodegradable plastic. There are two types currently on the market -- plant-based hydro-biodegradable plastic and petroleum-based oxo-biodegradable plastic. In the former category, polylactic acid (PLA), a plastic made from corn, tops the list as the most talked-about alternative. PLA decomposes into water and carbon dioxide in 47 to 90 days -- four times faster than a PET-based bag floating in the ocean. But conditions have to be just right to achieve these kinds of results. PLA breaks down most efficiently in commercial composting facilities at high temperatures. When buried in a landfill, a plastic bag made from corn may remain intact just as long as a plastic bag made from oil or natural gas.
Keep reading for more links you might like on plastics."
http://science.howstuffworks.com/science-vs-myth/everyday-myths/how-long-does-it-take-for-plastics-to-biodegrade1.htm
What could be wrong with a renewable resource you grow in a field and compost when you're done with it? As it turns out, several things. For one, corn plastic only composts in the hot, moist settings of a commercial composting facility. Simply throw a corn plastic product out of your car or bury it in a backyard-composting heap and the material will stand the test of time just as regular PET plastics will.
If commercial composting isn't available, PLA plastics can wind up following conventional plastics into the landfill or into plastic recycling programs. What's wrong with putting corn plastics in your recycling bin? To the uninformed eye, one may look very much like the other, but their chemical composition is very different. In fact, a relatively small amount of bioplastic can contaminate conventional plastic recycling, preventing the salvaged plastic from being reused and stopping recycling companies from profiting from one of their more lucrative recyclables.
Due to these dangers, companies like NatureWorks are treading carefully, introducing corn plastic products slowly and communicating with commercial recyclers to spot contamination early. Bioplastics manufacturers insist that the threat is overblown and that recycling remains a better option than composting for PLAs such as corn plastic, since it makes up such a small percent of the current plastics market. In addition, since PLA plastics produce the greenhouse gas methane when they decompose, composting isn't a perfect disposal method. On the other hand, if incinerated, bioplastics don't emit toxic fumes like their oil-based counterparts.
To avoid the complications of mixed plastics, commercial composters in the Northwestern United States only accept bioplastics from food service operations, not households. This approach means that bioplastics could conceivably be used to great effect at sports games and other events where foods are purchased and consumed on the premises in bulk.
As with corn ethanol, corn plastic has also drawn criticism for depending on the industrial farming of large fields of crops. These fields could otherwise be used to grow food for an ever-rising global population. Much of the corn used for bioplastics is a variety called Number 2 Yellow Dent that's used mostly for animal feed. In addition, some of this corn used has been genetically modified. Nevertheless, even if genetically modified corn was used to make your plastic water bottle, NatureWorks insists that you don't have to worry about consuming modified proteins, as these are destroyed in the transformation from plant to PLA plastic [source: Jewell].
Advocates also stress that the bioplastics industry is in its infancy, with long-term plans of being able to depend exclusively on agricultural waste (such as stems and stalks) for production. Such plans are also mentioned in defense of the higher costs associated with bioplastics research and production. PET plastics are a mature commodity, with years of production fine-tuning behind it. Bioplastics advocates argue that, in time, PLA costs will go down, all while petroleum-based plastics costs continue to fluctuate due to unstable production regions and dwindling resources.
Explore the links on the next page to learn even more about plastics, corn, biofuel and recycling.
http://science.howstuffworks.com/environmental/green-science/corn-plastic3.htm
Until other researchers can replicate Burd's experiment and waste treatment plants can implement any new processes, the only real way to break down plastic is through photodegradation. This kind of decomposition requires sunlight, not bacteria. When UV rays strike plastic, they break the bonds holding the long molecular chain together. Over time, this can turn a big piece of plastic into lots of little pieces.
Of course, plastic buried in a landfill rarely sees the light of day. But in the ocean, which is where a lot of discarded grocery bags, soft drink bottles and six-pack rings end up, plastic is bathed in as much light as water. In 2009, researchers from Nihon University in Chiba, Japan, found that plastic in warm ocean water can degrade in as little as a year. This doesn't sound so bad until you realize those small bits of plastic are toxic chemicals such as bisphenol A (BPA) and PS oligomer. These end up in the guts of animals or wash up on shorelines, where humans are most likely to come into direct contact with the toxins.
One solution to this environmental disaster is biodegradable plastic. There are two types currently on the market -- plant-based hydro-biodegradable plastic and petroleum-based oxo-biodegradable plastic. In the former category, polylactic acid (PLA), a plastic made from corn, tops the list as the most talked-about alternative. PLA decomposes into water and carbon dioxide in 47 to 90 days -- four times faster than a PET-based bag floating in the ocean. But conditions have to be just right to achieve these kinds of results. PLA breaks down most efficiently in commercial composting facilities at high temperatures. When buried in a landfill, a plastic bag made from corn may remain intact just as long as a plastic bag made from oil or natural gas.
Keep reading for more links you might like on plastics."
http://science.howstuffworks.com/science-vs-myth/everyday-myths/how-long-does-it-take-for-plastics-to-biodegrade1.htm
What is corn plastic?
"
For years, the corncob pipe was a fashion accessory best left to hillbillies, Frosty the Snowman and Gen. Douglas MacArthur. While the look is no less bumpkinish today than it ever was, corn is showing up in the production of more everyday items -- and without resembling a prop from "Hee Haw." What looks like normal oil-based plastic at first glance is actually polylactic acid (PLA) plastic made from specially processed crops.
That's right: corn plastic. You can drink coffee out of it, put groceries in it, wear it and even hang ten on it on a corn plastic surfboard. Most important, you can turn corn into plastic and avoid dependency on petroleum. Much like corn ethanol, corn plastic allows us to make a comparable product out of a renewable resource, as opposed to oil reserves that will one day run dry. In addition, since corn can be cultivated throughout the world, market value doesn't hinge on relationships with oil-rich nations or on peace in the Middle East. After all, have you ever seen "No blood for corn" printed on a T-shirt?
The United States uses 20.8 million barrels of oil per day, 10 percent of which goes solely to the production of conventional plastic such as polyethylene terephthalate (PET) [sources: CIA World Factbook, Jewell]. Bioplastics like corn plastic, however, don't require oil and, as a bonus, their manufacture releases fewer toxins and greenhouse gases.
Plus, while normal plastic has a nasty habit of sticking around for centuries after disposal, corn plastic boasts the ability to biodegrade in mere months. Moreover, should you choose to burn it, you don't have to worry about creating toxic fumes.
In this article, we'll look at how a corn stalk turns into a plastic garbage can and why some critics aren't convinced that bioplastics are necessarily a godsend.
For years, the corncob pipe was a fashion accessory best left to hillbillies, Frosty the Snowman and Gen. Douglas MacArthur. While the look is no less bumpkinish today than it ever was, corn is showing up in the production of more everyday items -- and without resembling a prop from "Hee Haw." What looks like normal oil-based plastic at first glance is actually polylactic acid (PLA) plastic made from specially processed crops.
That's right: corn plastic. You can drink coffee out of it, put groceries in it, wear it and even hang ten on it on a corn plastic surfboard. Most important, you can turn corn into plastic and avoid dependency on petroleum. Much like corn ethanol, corn plastic allows us to make a comparable product out of a renewable resource, as opposed to oil reserves that will one day run dry. In addition, since corn can be cultivated throughout the world, market value doesn't hinge on relationships with oil-rich nations or on peace in the Middle East. After all, have you ever seen "No blood for corn" printed on a T-shirt?
The United States uses 20.8 million barrels of oil per day, 10 percent of which goes solely to the production of conventional plastic such as polyethylene terephthalate (PET) [sources: CIA World Factbook, Jewell]. Bioplastics like corn plastic, however, don't require oil and, as a bonus, their manufacture releases fewer toxins and greenhouse gases.
Plus, while normal plastic has a nasty habit of sticking around for centuries after disposal, corn plastic boasts the ability to biodegrade in mere months. Moreover, should you choose to burn it, you don't have to worry about creating toxic fumes.
In this article, we'll look at how a corn stalk turns into a plastic garbage can and why some critics aren't convinced that bioplastics are necessarily a godsend.
Bioplastics: The Pros and Cons
Globally, bioplastics make up nearly 331,000 tons (300,000 metric tons) of the plastics market [source: European Bioplastics]. That may sound like a lot, but it only accounts for less than 1 percent of the 200 million tons (181 million metric tons) of synthetic plastics the world produces each year [source: Green Council]. Still, the bioplastics market is growing by 20 to 30 percent each year, but not everyone's pleased [source: Vidal].What could be wrong with a renewable resource you grow in a field and compost when you're done with it? As it turns out, several things. For one, corn plastic only composts in the hot, moist settings of a commercial composting facility. Simply throw a corn plastic product out of your car or bury it in a backyard-composting heap and the material will stand the test of time just as regular PET plastics will.
If commercial composting isn't available, PLA plastics can wind up following conventional plastics into the landfill or into plastic recycling programs. What's wrong with putting corn plastics in your recycling bin? To the uninformed eye, one may look very much like the other, but their chemical composition is very different. In fact, a relatively small amount of bioplastic can contaminate conventional plastic recycling, preventing the salvaged plastic from being reused and stopping recycling companies from profiting from one of their more lucrative recyclables.
Due to these dangers, companies like NatureWorks are treading carefully, introducing corn plastic products slowly and communicating with commercial recyclers to spot contamination early. Bioplastics manufacturers insist that the threat is overblown and that recycling remains a better option than composting for PLAs such as corn plastic, since it makes up such a small percent of the current plastics market. In addition, since PLA plastics produce the greenhouse gas methane when they decompose, composting isn't a perfect disposal method. On the other hand, if incinerated, bioplastics don't emit toxic fumes like their oil-based counterparts.
To avoid the complications of mixed plastics, commercial composters in the Northwestern United States only accept bioplastics from food service operations, not households. This approach means that bioplastics could conceivably be used to great effect at sports games and other events where foods are purchased and consumed on the premises in bulk.
As with corn ethanol, corn plastic has also drawn criticism for depending on the industrial farming of large fields of crops. These fields could otherwise be used to grow food for an ever-rising global population. Much of the corn used for bioplastics is a variety called Number 2 Yellow Dent that's used mostly for animal feed. In addition, some of this corn used has been genetically modified. Nevertheless, even if genetically modified corn was used to make your plastic water bottle, NatureWorks insists that you don't have to worry about consuming modified proteins, as these are destroyed in the transformation from plant to PLA plastic [source: Jewell].
Advocates also stress that the bioplastics industry is in its infancy, with long-term plans of being able to depend exclusively on agricultural waste (such as stems and stalks) for production. Such plans are also mentioned in defense of the higher costs associated with bioplastics research and production. PET plastics are a mature commodity, with years of production fine-tuning behind it. Bioplastics advocates argue that, in time, PLA costs will go down, all while petroleum-based plastics costs continue to fluctuate due to unstable production regions and dwindling resources.
Explore the links on the next page to learn even more about plastics, corn, biofuel and recycling.
http://science.howstuffworks.com/environmental/green-science/corn-plastic3.htm
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