# Is there any use for biodegradables where trash is incinerated? **URL:** \ **Category:** Factual Questions\ **Created:** [April 3, 2012, 8:10am UTC](https://boards.straightdope.com/t/is-there-any-use-for-biodegradables-where-trash-is-incinerated/617672 "2012-04-03T08:10:33Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![AaronX](https://avatars.discourse-cdn.com/v4/letter/a/7bcc69/32.png) [@AaronX](https://boards.straightdope.com/u/AaronX)\ **Post date:** [April 3, 2012, 8:10am UTC](https://boards.straightdope.com/t/is-there-any-use-for-biodegradables-where-trash-is-incinerated/617672/1 "2012-04-03T08:10:33Z")
I know biodegradables (e.g. plastic bags) cost more to make, and I heard they’re weaker so they have to be made thicker than normal plastic bags, which probably costs more to ship. Is there any point in using biodegradables when they’re going to be incinerated anyway? Actually, I thought landfills are designed NOT to let things decompose. If that were true, what’s the point of biodegradables at all, other than composting bags? ---
**Author:** ![Reply](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/reply/32/15952_2.png) [@Reply](https://boards.straightdope.com/u/Reply)\ **Post date:** [April 3, 2012, 8:56am UTC](https://boards.straightdope.com/t/is-there-any-use-for-biodegradables-where-trash-is-incinerated/617672/2 "2012-04-03T08:56:50Z")
[Wikipedia summarizes an FTC comment](https://en.wikipedia.org/wiki/Biodegradable_bag#Marketing_Qualification_and_Legal_Issues) on the matter: > [@](#): > > Example 1: A trash bag is marketed as “degradable,” with no qualification or other disclosure. The marketer relies on soil burial tests to show that the product will decompose in the presence of water and oxygen. The trash bags are customarily disposed of in incineration facilities or at sanitary landfills that are managed in a way that inhibits degradation by minimizing moisture and oxygen. Degradation will be irrelevant for those trash bags that are incinerated and, for those disposed of in landfills, the marketer does not possess adequate substantiation that the bags will degrade in a reasonably short period of time in a landfill. The claim is therefore deceptive Essentially, if it’s going to be landfilled or incinerated, it’s not going to do much. If it’s going to be incinerated, there MIGHT be small differences in air pollution and/or energy recoverability (when trash is burned to generate power), but I haven’t done the math so I don’t know. In those situations, which are probably the most common, it’s essentially greenwashing. Wikipedia also talks about how certain degradable bags break down into smaller pieces without ever being fully broken down, and when this gets into the environment (such as in trash gyres), wildlife can and do consume the pieces. Regular plastic bags photodegrade from sunlight, too, so I’m not sure which is worse for animals. So what’s the point of it all? Marketing, mainly. Green sells. Greenwashing sells too and costs less to do. Perhaps, in some cities, biodegradable bags can hold household compost and/or green waste and then be subsequently biodegraded in an industrial-grade composting facility that has the temperature and microbial activity necessary to properly digest it. But really, if you have that kind of system already, why not just use metal cans and skip the wasteful bag liner altogether? It’s the same deal as biodegradable utensils – more of a stop-gap band-aid for people who don’t want to deal with reusables. TL;DR: Biodegradable plastics are more expensive, occasionally a little less wasteful, and much more capable of making people feel better about consumption, which in turn makes businesses more money. ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [April 3, 2012, 12:11pm UTC](https://boards.straightdope.com/t/is-there-any-use-for-biodegradables-where-trash-is-incinerated/617672/3 "2012-04-03T12:11:46Z")
I thought the point of the BD plastics is that they will break down if discarded into the environment. ---
**Author:** ![gotpasswords](https://avatars.discourse-cdn.com/v4/letter/g/c57346/32.png) [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)\ **Post date:** [April 3, 2012, 2:56pm UTC](https://boards.straightdope.com/t/is-there-any-use-for-biodegradables-where-trash-is-incinerated/617672/4 "2012-04-03T14:56:54Z")
They’ll break down **if left out in the open**. The gotcha to the greenwashing is that nobody wants to leave plastic bags exposed to the elements long enough to break down - eventually they get picked up and discarded. Once they hit landfill, the degradation stops. Pretty much nothing breaks down appreciably in a modern landfill - even things you’d expect to disintegrate like newspapers can survive intact for years. About the only exception to this is bags that get blown around and snagged in dangerous or difficult places to clean like barbed-wire fences or powerlines - they’ll eventually break into pieces small enough to get loose, but then you just have more pieces of garbage. It’s not like the bags are made of ice that will cleanly evaporate away. ---
**Author:** ![purplehorseshoe](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/purplehorseshoe/32/2996_2.png) [@purplehorseshoe](https://boards.straightdope.com/u/purplehorseshoe)\ **Post date:** [April 3, 2012, 4:38pm UTC](https://boards.straightdope.com/t/is-there-any-use-for-biodegradables-where-trash-is-incinerated/617672/5 "2012-04-03T16:38:08Z")
What about digestibility? They say a lot of sea turtles are killed by floating plastic bags, which look like jellyfish to them and cause intestinal blockages if consumed. Do these help that issue? ---
**Author:** ![Reply](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/reply/32/15952_2.png) [@Reply](https://boards.straightdope.com/u/Reply)\ **Post date:** [April 3, 2012, 8:40pm UTC](https://boards.straightdope.com/t/is-there-any-use-for-biodegradables-where-trash-is-incinerated/617672/6 "2012-04-03T20:40:45Z")
> [@purplehorseshoe](#): > > What about digestibility? They say a lot of sea turtles are killed by floating plastic bags, which look like jellyfish to them and cause intestinal blockages if consumed. Do these help that issue? There is [a paper that addresses this very question](https://encrypted.google.com/url?sa=t&rct=j&q=digestability+of+biodegradable+bags&source=web&cd=1&ved=0CHsQFjAA&url=http%3A%2F%2Fplasticsoupfoundation.org%2Fwp-content%2Fuploads%2F2012%2F01%2FExperimental-degradation-of-polymer-shopping-bags-standard-and-degradable-plastic-and-biodegradable-in-the-gastrointestinal-fluids-of-sea-turtles.pdf&ei=n197T6zBD6mY2wXnp_XECQ&usg=AFQjCNF4Vt73P7KEfQAECW-e5P9EiCue7A&sig2=YEvQ3ct8nifsioRVT5mQpw). From the abstract: > [@](#): > > This study set out to test the decay characteristics of three common types of shopping bag polymers in sea turtle gastrointestinal fluids (GIF): standard and degradable plastic, and biodegradable. Fluids were obtained from the stomachs, small intestines and large intestines of a freshly dead Green turtle (Chelonia mydas) and a Loggerhead turtle (Caretta caretta). Controls were carried out with salt and freshwater. The degradation rate was measured over 49 days, based on mass loss. Degradation rates of the standard and the degradable plastic bags after 49 days across all treatments and controls were negligible. **The biodegradable bags showed mass losses between 3 and 9%. This was a much slower rate than reported by the manufacturers in an industrial composting situation (100% in 49 days)**. The GIF of the herbivorous Green turtle showed an increased capacity to break down the biodegradable polymer relative to the carnivorous Loggerhead, but at a much lower rate than digestion of natural vegetative matter. While the breakdown rate of biodegradable polymers in the intestinal fluids of sea turtles is greater than standard and degradable plastics, **it is proposed that this is not rapid enough to prevent morbidity**. Further study is recommended to investigate the speed at which biodegradable polymers decompose outside of industrial composting situations, and their durability in marine and freshwater systems. Wikipedia noted that some of the degradable/biodegradable bags have an increased tendency to fragment, which might contribute to more of it being eaten by wildlife than whole/more complete bags. But, again, regular plastic degrades in the sun, too, so in the end it I’m guessing that it might not be much of a difference either way. ---
**Author:** ![Reply](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/reply/32/15952_2.png) [@Reply](https://boards.straightdope.com/u/Reply)\ **Post date:** [April 3, 2012, 8:55pm UTC](https://boards.straightdope.com/t/is-there-any-use-for-biodegradables-where-trash-is-incinerated/617672/7 "2012-04-03T20:55:12Z")
Here’s another non-scientific [whitepaper](http://www.europeanplasticfilms.eu/docs/AustralianReportonBiodegradablePlastics.pdf) (I think) that talks more about the various effects. Some quotes: > [@](#): > > Pollution from high nutrient levels in waterways, determined by high biological oxygen demand (BOD) and chemical oxygen demand (COD), lead to the degradation of aquatic ecosystems and algal blooms. The breakdown of starch-based biodegradable plastic materials can result in increased BOD if the plastics make their way into water ways. > > [Reply: BOD is a rough measure of aquatic biological activity, which can sound benign, but if you have too much nutrients in an area over too short a period of time, it can lead to algal blooms that suck up available oxygen and kill off other aquatic life in the area.] > > […] > > Groundwater contamination from pigments, catalyst residues and isocyanate coupling agents may also occur. Liberated plastic additives and polymer degradation products in landfills or compost heaps can potentially migrate to nearby bodies of water through liquids percolating in the ground (leaching) or via rainfall run-off. If current metal-based pigments continue to be used in biodegradable plastics, then the potential for release and accumulation in soil and water is high. > > […] > > The visual impact of littering is unlikely to decrease with the use of biodegradable plastics since windblown plastic litter and plastic films/bags snagged on branches and bushes will not be exposed to sufficient level of microbes for proper biodegradation to take place. Consequently biodegradation of such litter may take many years. > > [Reply: This is really the gist of it. They’re only really useful in industrial (meaning high volume, high heat) composting facilities, which most areas don’t have. The areas that do are typically eco-minded enough such that convincing them to use reusable containers wouldn’t be too far a stretch, so where would these bags really be useful?] > > […] > > Biodegradable plastics based on conventional thermoplastics that contain prodegradant additives (refer to Section 4.3) may cause negative environmental impacts because they: > > - are not based on renewable resources; > - have the potential to disperse catalytic metals in to the environment; > - convert carbon from a carbon sink (oil) to atmospheric carbon and thus contribute to net greenhouse gas inventories; and > - disintegrate into tiny particles and do not truly biodegrade and the small fragments that remain still have too high a molecular weight to break down to low molecular weight materials. Blah blah blah. There are pages of this stuff in that report.