The Truth About Plastic Bags Decomposing

The Daily Green:

Dear EarthTalk: I've heard conflicting reports regarding how long it really takes for a plastic grocery bag to decompose. Can you set the record straight? --

Read the whole story: The Daily Green

Comments

[Minolta]

10:25 AM on 10/04/2010

Every day, at every meal, I toss all that packaging into the trash.

We really must develop food packaging that keeps us safe from infections yet can ultimately always degrade or be recycled. Our disposable packaging simply must become recycled packaging.

[jsarets]

04:21 AM on 10/04/2010

Many of the "biodegradable" plastics available today have one of two problems: they either weaken or dissolve in water (not so good in contact with moist foods), or they only decompose in sophisticated industrial composting facilities (not in traditional home composting bins).

The post-consumer recycling rate for plastic bags is terrible (0.6%), and depending on consumers to properly dispose of special "biobags" so that they find their way to industrial composting facilities is an even taller order than conventional #2 plastic recycling.

There's a great way to "downcycle" any kind of plastic.  It's called hydrous pyrolysis or thermal depolymerization.  The plastic is heated with water under pressure and then depressed, yielding 76% liquid hydrocarbons (gasoline, kerosene, and diesel), 17% gaseous hydrocarbons (mostly methane and hydrogen), and 7% solid charcoal.

The best part is that this kind of facility can also process cellulosic waste, yielding 60% gases, 30% solids, and 10% liquids.  It can also process wastewater sludge, yielding 60% liquids, 21% gases, and 19% solids.  The process is 85% efficient and can be completely fueled by output gases.

So a hydrous pyrolysis facility can handle the wastewater stream, the agricultural waste stream, and most of the municipal solid waste stream, excluding metal and glass.  That cuts down on sorting complexity.  Metal, glass, and everything else: paper, plastic, food scraps, etc.

The output, of course, is fuel, electricity and fertilizer (the charcoal is excellent for soil).

If we can manage a plastic-friendly waste disposal system, then polyethylene is definitely one of the preferable plastics.  It's actually easier to produce polyethylene from ethanol than from petroleum, and in Brazil, polyethylene from sugarcane ethanol is commonplace.  

[HummusGringo]

12:47 AM on 10/04/2010

Everyone here should make themselves aware of this young man's discovery:

http://www.wired.com/wiredscience/2008/05/teen-decomposes/

It could be extremely beneficial!

[evekendall]

11:02 PM on 10/03/2010

Turtle eating a plastic bag:
http://blog.iesve.com/wp-content/uploads/2009/02/turtle_eating_plastic_bags.jpg

Plastic bags blow:
http://www.flickr.com/groups/plasticbagsblow/pool/52452851@N00/

[tarlipps]

10:57 PM on 10/03/2010

If everything manufactured was charged a cash deposit when purchased they could close all the dumps.

[evekendall]

10:48 PM on 10/03/2010

"Fast Facts on Plastic Bags"
http://www.reuseit.com/learn-more/top-facts/plastic-bag-facts

[rjmtx]

07:27 PM on 10/03/2010

What about our disposable plastic computers? Heh heh...

[Holly Rayl]

05:19 PM on 10/05/2010

Ugh. I HATE our planned obsolescence society.

[Genders]

07:21 PM on 10/03/2010

Plastics don't really decompose. Plastic particles have been found within the cells of animals and plants, functionless, but taking up space. We are asking for it by dumping our plastics into the environment. As Jeff Godlbloom said "life will find a way" to eat that plastic, and then all the benefits of plastics will be lost, and our modern high tech society crippled. All organic waste, including plastics, should be recycled, then converted to bio fuels when recycling is no longer practical.

[vetxcl]

07:00 PM on 10/03/2010

http://www.associatedbag.com/ShowItems.asp?oid=34854692&cookie%5Ftest=1

[vetxcl]

06:56 PM on 10/03/2010

http://www.friendlybags.com/

[vetxcl]

06:56 PM on 10/03/2010

http://www.biobagusa.com/

[smitty101]

05:01 PM on 10/03/2010

I am switching to paper when asked.

[BannedFiveTimes]

04:26 PM on 10/03/2010

Contrary to the general belief and contrary to what the Greenies tell all of us... Landfills are the most effective, efficient and Eco friendly way of disposing any material. Nature takes its own time sweet in decomposing it, but it will do it.
If you want to speed up the process alternate plastics and organics in the land fill.

[quillsinister]

08:39 PM on 10/03/2010

Biodegradation does not happen with plastic. By whatever logic microorganisms use to peruse the menu, plastic isn't on it. And if you bury the stuff you've just taken photodegradation off of the table as well. That might not be bad in itself, since having tiny particles of plastic infiltrating every level of the food chain probably isn't the best thing in the world (and remember that toxins reach greater concentrations the higher up the food chain you happen to be), but you're either a scientific ignoramus or simply lying to make an argument like the one you just posted.

[Galong]

10:18 PM on 10/03/2010

A lot of us "Greenies" as you call us, like science. Can you possibly provide any scientific prove to support your position, please?

[tarlipps]

10:49 PM on 10/03/2010

Of course not................it's against the law.

[bryanzth]

03:47 PM on 10/03/2010

Plastic bags don't die, they just slowly fade away into the Pacfic Garbage Pile (Pacific Gyre) or into similar places in the World Ocean.

http://www.thedailygreen.com/environmental-news/latest/plastic-bag-decompose?src=rss

"Researchers fear that such ubiquitous bags may never fully decompose; instead they gradually just turn into smaller and smaller pieces of plastic... When exposed to sunshine, polyethylene's polymer chains become brittle and crack, eventually turning what was a plastic bag into microscopic synthetic granules. Scientists aren't sure whether these granules ever decompose fully, and fear that their buildup in marine and terrestrial environments -- and in the stomachs of wildlife -- portend a bleak future compromised by plastic particles infiltrating every step in the food chain. A plastic bag might be gone in anywhere from 10 to 100 years (estimates vary) if exposed to the sun, but its environmental legacy may last forever."

Remember the Pacific Gyre that is in the North Pacific? The plastic bits go in the street, down the storm drain, down the sewer, down the Hudson River, down the Mississippi River (NOLA), down the Sacramento River (SF), down the Fraser River (Vancouver), down the River Rimac (it goes through Lima) or down the Los Angeles River, and into the oceans.  The bits gradually become concentrated in central currents in the Atlantic and Pacific, which now contain trillions of bits and pieces of plastic that plankton, small fish and larger animals ingest. This material eventually kills the little organisms and then strangles the intestines of the predator fish, shark or mammal larger animals.

Pacific Gyre (Pacific Garbage Patch):
http://en.wikipedia.org/wiki/Great_Pacific_Garbage_Patch

Sargasso Sea (another garbage pile):
http://en.wikipedia.org/wiki/Sargasso_sea

Gulf of Mexico (a big garbage pile):
http://en.wikipedia.org/wiki/Gulf_of_mexico

Plastic, the new food filler! But seriously, does the "decomposable bag" just keep politicians and plastic bag manufacturers out of the spotlight? Hm?

BZ.

[rikster]

03:20 PM on 10/03/2010

they don't....