Bioplastics

The first plastic garbage bag was invented by Harry Waslyk in 1950.

1950!  Mr. Waslyk could not have predicted how much havoc his plastic child would wreck in a mere 62 years.[1]

We’ve all seen the pictures of birds stomachs filled with plastic detritus and read about the Great Pacific Gyre, but I just read a new twist to that story:    the Emirates News Agency reported that decomposed remains of camels in the desert region of the United Arab Emirates revealed that 50% of the camels died from swallowing and choking on plastic bags.  “Rocks of calcified plastic weighing up to 60 kilograms are found in camel stomachs every day,” said Dr. Ulrich Wernery, Scientific Director, Central Veterinary Research Laboratory in Dubai, whose clinic conducts hundreds of post-mortems on camels, gazelles, sheep and cows in the UAE.  He adds that one in two camels die from plastic.[2]

Plastic has become so ubiquitous, in fact, that plastics are among the debris orbiting our planet. Unfortunately, our wildlife and domestic animals are paying the price now; I think we ourselves will see changes in future generations.

It’s no wonder we’re scrambling to find alternatives to plastic, and one hot topic in the research area is that of bioplastics.

Bioplastics are made (usually) from plant materials.  Enzymes are used to break starch in the plant into glucose, which is fermented and made into lactic acid.  This lactic acid is polymerized and converted into a plastic called polylactic acid (PLA), which can be used in the manufacture of products  ( PLA is about 20% more expensive than petroleum-based plastic)  or into a plastic  called polyhydroxyalkanoate, or PHA (PHA biodegrades more easily but is more than double the price of regular plastic).

The bioplastic market is expanding rapidly and by 2030, according to some estimates, could account for 10% of the total plastics market.   In the world of fabrics and furnishings, the new biotech products which are being heavily promoted are Ingeo and Sorona, both PLA based fibers with a growing share of the fabric market; and soy-based foam for upholstery.    Toray Industries has announced that they will have the first functional performance nylon and polyester textiles based on biomass ready for the 2013/14 season.  They are 100% bio-based fabrics [3] based on the castor plant, which is very robust, growing in dry farming areas and requiring significantly fewer pesticides and herbicides than other crops.

So it’s no wonder that there has been much discussion about bioplastics, and about whether there are ecological advantages to using biomass instead of oil.

The arguments in favor of bioplastics are:

• They are good for the environment because there is no harm done to the earth when recovering fossil fuels. Also, in this process there are very few greenhouse gas and harmful carbon emissions. Regular plastics need oil for their manufacturing, which pollutes the environment.
• They require less energy to produce than petroleum-based plastics.
• They are recyclable.
• They are non toxic.
• They reduce dependence on foreign oil.
• They are made from renewable resources.

These arguments sound pretty good – until you begin to dig  and find out that once again, nothing is ever as simple as it seems.

Regarding the first two arguments (they are good for the environment because they produce significantly fewer CO2 emissions and less energy) -  there have not been many studies which support  this argument until recently.  Recently,  several  studies have been published which seems to support that  this is indeed the case:

1. Ramani Narayan of Michigan State University found that “the results for the use of fossil energy resources and GHG emissions are more favorable for most bio based polymers than for oil based. As an exception, landfilling of biodegradable polymers can result in methane emissions (unless landfill gas is captured) which may make the system unattractive in terms of reducing greenhouse gas emissions.”[4]
2. University of Pittsburgh researchers did an LCA on the environmental impacts of both petroleum and bio derived plastics, assessing them using metrics which included  economy, mass from renewable sources, biodegradability, percent recycled, distance of furthest feedstock, price, life cycle health hazards and life cycle energy use. They found that  biopolymers are the more eco-friendly material in terms of energy use and emissions created.  However, they also concluded that traditional plastics can actually be less environmentally taxing to produce when taking into account such things as acidification, carcinogens, ecotoxicity, eutrophication, global warming, smog, fossil fuel depletion, and ozone depletion.[5]
3. A study done by the nova-Institut GmbH on behalf of Proganic GmbH & Co.[6]showed unambiguously positive eco advantages (in terms of energy use and CO2 emissions) for bio based polymers PLA and PHA/PHB over petrochemical based plastics.  According to the report, “the emission of greenhouse gases and also the use of fossil raw materials are definitely diminished. Therefore the substitution of petrochemical plastics with bio-based plastics yields positive impacts in the categories of climate change and depletion of fossil resources.”  The results include:
   1. Greenhouse gas emissions of bio-based plastics amount to less than 3 KG of CO2 equivalents per KG of plastic, less than that of petrochemical based plastics which produce an average of 6 KG of CO2 equivalents per KG of plastic..
   2. the production of bio-based polymers, in comparison to all petrochemical plastics examined, leads to savings in fossil resources. The biggest savings potential can be found in comparison with polycarbonate (PC). The average savings potential in the production of PLA amounts to 56 ± 13 megajoules per kilogram of plastics here.
   3. The production of bio-based polymers in comparison with the production of petrochemical plastics in most cases also leads to greenhouse gas emission savings. The biggest greenhouse gas emission savings can be found again when comparing bio-based polymers to polycarbonate (PC). For PLA, the average savings potential in this case amounts to 4.7 ± 1.5 kilograms of CO2 equivalents per kilogram of plastics. For PHA, the average savings potential in this case amounts to 5.8 ± 2.7 kilograms of CO2 equivalents per kilogram of plastics. In comparison with PET and Polystyrene (PS), considerable savings potentials ranging between 2.5 and 4.2 kilograms of CO2 equivalents per kilogram of plastics are to be found in the production of bio-based polymers. The lowest savings potential are to be found when comparing bio-based polymers with polypropylene (PP).

So I will accept the arguments that biobased plastics produce fewer  greenhouse gases and harmful carbon emissions and require less energy to produce than petroleum-based plastics .  They also certainly reduce our dependence on foreign oil.

But are they better for the environment?  Are they recyclable or biodegradeable?  Are they safe?  Are plastics producers aware of the impact of promoting bioplastics as a replacement for plastics? We think that  bioplastics are useful for certain purposes, such as medical sutures or strewing foil for mulching in agriculture – but as a replacement for all plastics?

Next week we’ll take a look at the arguments against bioplastics.

---

[1] Laylin, Tafline, “Half of UAE’s Falaj Mualla Camels Choked on Plastic Bags”, Green Prophet blog, June 11, 2010.

http://www.greenprophet.com/2010/06/camels-choke-on-plastic/

[2] Ibid.

[3] http://www.ecotextile.com/2012020811377/materials-production-news/biomass-fabrics-for-sportswear-within-two-years.html

[4] Narayan, Ramani, “Review and Analysis of Bio-based Product LCA’s”, Department of Chemical Engineering & Materials Science, Michigan State University, East Lansing, MI 48824

[5] Tabone, Michaelangelo D., et al; “Sustainability Metrics: Life Cycle Assessment and Green Design in Polymers”, Enviornmental Science and Technology, September 2, 2010.

[6]http://www.google.com/url?sa=t&rct=j&q=&esrc=s&frm=1&source=web&cd=1&ved=0CCEQFjAA&url=http%3A%2F%2Fwww.nova-institut.de%2Fdownload%2FMeta-LCA%2520PR&ei=ihJ-T_C7K5HRiAKlrIzlDQ&usg=AFQjCNFQ9rxS2G0YQ3dlrlsskwoXnFbCmQ

Biodegradeable or compostable?

There is no legal definition of “biodegradable,” so the term has been used loosely by some manufacturers.  The American Society for Testing and Materials defines the term as “a degradation caused by biological activity, especially by enzymatic action, leading to a significant change in the chemical structure of the material.”

The Biodegradable Products Institute (BPI) cites a 2006 American Chemistry Council study showing that most consumers believe a product labeled “biodegradable” will go away completely and on its own in a year or less. The BPI says many consumers also believe that these products will “biodegrade” in landfills.

Because it seems a desirable product attribute, the term “biodegradable” has been applied to a wide range of products—even those that might take centuries to decompose, or those that break down into harmful environmental toxins.   Biodegradability is definitely perceived as  a positive trait, yet it could be applied to virtually anything because anything is biodegradable, given enough time.  The Federal Trade Commission (FTC) in the U.S., however, has issued some general guidelines on what types of products qualify as legitimately biodegradable, and has even sued companies for unsubstantiated, misleading and/or deceptive use of the term on product labels.

According to the FTC, only products that contain materials that “break down and decompose into elements found in nature within a reasonably short amount of time after customary disposal” should be marketed as “biodegradable.”

But the FTC acknowledges that even products appropriately labeled as biodegradable may not break down easily if they are buried under a landfill or are otherwise not exposed to sunlight, air and moisture, the key agents of biodegradation. In fact, in landfills materials degrade very, very slowly – if at all!  This is because modern landfills are designed, according to law, to keep out sunlight, air and moisture – the very ingredients needed for materials to biodegrade. This helps prevent pollutants from the garbage from getting into the air and drinking water, and slows the decomposition of the trash. In Dr. William Rathje’s book entitled “Rubbish,” he sites that “The truth is, however, that the dynamics of a modern landfill are very nearly the opposite of what most people think…Well designed and managed landfills seem to be far more apt to preserve their contents for posterity than transform them into humus or mulch. They are not vast composters: rather they are vast mummifiers.” In his book, Dr. Rathje talks about doing excavations on 15 landfills throughout North America. From those digs, they found 40 year old newspapers that were still legible, 5 year old lettuce and a 15 year old hot dog. From these studies it seems fairly clear that even organic materials take a very long time to break down in landfills let alone plastic or other items.  The reality is if any product ends up in a landfill, it will not degrade.

But the fact that a product breaks down – if it does indeed break down – may not be as important as what the product breaks down into. In a perfect would all products would break down to CO2 and H2O. But it gets more complicated as we increase the number and kinds of chemicals. The banned pesticide DDT is hazardous and toxic in its own right. And it does biodegrade, though rather slowly. The problem is that its breakdown products of DDD and DDE are even more toxic and dangerous than the original DDT.
So just because a product or ingredient is biodegradable does not mean it is healthy or safe for people or the environment – especially if it leaches harmful chemicals into the ecosystem. Under this definition, even regular oil based plastic can be advertised as “biodegradable” because at some point, sooner or later, it is going to break down into small pieces.

“Compostable”, on the other hand, has a definition that is rigorously governed by the standards ASTM D-6400, ASTM D6868, and EN13432.   The term “compostable” covers four areas:

1.      Biodegradable – i.e.,  60 – 90% of the product will break down into CO2 within 180 days in a commercial composting facility.

2.      Disintegration – this requires that 90% of the product will break down into pieces that are 2mm or smaller

3.      Eco-toxicity – the product will not deposit heavy metals that are toxic to the soil beyond that found in typical compost.

4.      Compostable products have the added implication that when they break down they turn into humus, which provides valuable nutrients to the soil.

So, while some products are considered biodegradable, they may not be considered compostable because they either don’t meet the heavy metal requirements,  don’t break down in a timely fashion or don’t contribute valuable nutrients which improves the soil.

Composting of organic waste makes sense, but compostable plastic for shopping bags, food packaging, fabric, etc. does not, because:

1.      It is up to 400% more expensive than ordinary plastic;

2.      it is thicker and heavier and requires more trucks to transport it;

3.      recycling with oil-based plastics is impossible;

4.      it uses scarce land and water resources to produce the raw material, and substantial amounts of non-renewable hydro-carbons are burned and CO2 emitted, by the tractors and other machines employed.

5.      If buried in landfill, compostable plastic can emit methane (a greenhouse gas 23 times more powerful than CO2) in anaerobic conditions.

Many industrial composters of organic waste around the world do not want plastic of any kind in their feedstock, because it is difficult to separate biodegradable plastic from ordinary plastic. Home composting of plastic is not encouraged, as it will often be contaminated with food residues, and temperatures may not rise high enough to kill the pathogens. Compostable plastic is useless in compost because 90% of it has to convert to CO2 gas in order to comply with ASTM D6400 and the other composting Standards. It therefore contributes to greenhouse gases but not to the improvement of the soil.

Meanwhile, you can follow Dave, who  buried an advertised Paper Mate  biodegradable pencil in his backyard last summer and says he will report on it’s degradation over time.  Click here to read more and follow the story!

So how does this apply to fabrics?  Well, for starters the companies that make PLA (polylactic acid) based polymers – those corn based bio plastics – advertise that their products are biodegradable.   PLA is said by the manufacturer  to decompose into carbon dioxide and water in a “controlled composting environment” in fewer than 90 days. What’s a controlled composting environment? It’s not exactly your average backyard bin, pit or tumbling barrel. It’s a large facility where compost—essentially, plant scraps being digested by microbes into fertilizer—reaches 140 degrees for ten consecutive days. So, yes, as PLA advocates say, corn plastic is “biodegradable.” But in reality very few consumers have access to the sort of composting facilities that can make that happen. NatureWorks (the largest manufacturer of PLA, owned by Cargill Dow)  has identified only  113 such facilities nationwide.

Moreover, PLA by the truckload may potentially pose a problem for some large-scale composters.  And there is no evidence that  PLA breaks down any faster than PET or other plastics in a normal landfill environment.  (Read more about PLA and biodegradability here.)

And unless the chemicals used during processing of your fabric are such that there are no chemicals which would combine with other chemicals to form molecules of anything other than water, carbon dioxide and safe organic material – then it cannot be called compostable.  If the chemicals used during processing contain, for example, heavy metals in the dyestuffs – then those metals become available to your plants in the garden – and that again knocks it out of the “compostable” set of products.  That might be o.k. if you’re growing roses rather than radishes, but if you plan to eat those plants I’d look elsewhere as a way to dispose of your fabric.  Certified fabrics  made of natural fibers which look at the chemical inputs of processing (such as GOTS and Oeko Tex) would be o.k. for use in a vegetable garden – because they have been tested to be free of toxic inputs – and they could be called “compostable”.

Resources:

The Biodegradable Products Institute, www.bpiworld.org

US Composting Council  www.compostingcouncil.org