What is the benefit of PLA?

9 10 2018

Much of this article came from the Smithsonian Magazine written by Elizabeth Royte – to whom we owe our gratitude.

Near Blair, Nebraska is the largest lactic acid plant in the world.  Into one end goes corn, and out the other comes white pellets, which some say is the future of plastic.  The substance is PLA – Polymerized Lactic Acid, or polylactic acid.

Globally, bioplastics (of which PLA is a member) make up nearly 331,000 tons (300,000 metric tons) of the plastics market.[1]  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. Still, the bioplastics market is growing by 20 to 30 percent each year.[2]  In the US, plastics take up 25% of landfilles by volume.[3]

Even the Biodegradable Products Institute notes that NOTHING biodegrades in a landfill because nothing is supposed to. Furthermore the Biodegradable Products Institute notes that “Uncontrolled biodegradation in a landfill can cause ground water pollution, methane gas emissions and unstable sub-soil conditions.”

The benefit of PLA is that is that it’s made from Midwestern corn, not Middle East oil[4]. It’s a renewable resource, but more than 93% of the corn produced in the USA is genetically modified in some way.  NatureWorks (owned by Cargill, the world’s largest corn merchant) insists that you don’t have to worry about consuming genetically modified proteins because these are destroyed in the transformation from plant to PLA plastic.[5]  NatureWorks, acknowledging some of those criticisms, points out that the corn it uses is low-grade animal feed not intended for human use. And it processes a small amount of non-genetically engineered corn for customers who request it.[6]

Producing PLA uses 65% less energy than producing conventional plastics, according to an independent analysis commissioned by NatureWorks. It also generates 68% fewer greenhouse gases.  And, if incinerated, bioplastics don’t emit toxic fumes like their oil-based counterparts.

PLA does releases toxicfumes known as VOCs (Volatile Organic Compounds). Not all VOCs are actually toxic, but some may be, especially for younger users. Before this becomes a serious health issue, a new study has analysed the exact quantities of toxic VOCs – as well as potentially dangerous nanoparticles – in order to assess the potential health risks. The new study, presented by Dr. Fabrizio Merlo and Dr. Eng. Stefano Mazzoni, starts off from other previous research conducted in the early 90’s, which demonstrated that during the fusion and processing of plastic materials, several toxic particles are released as gases, including ammonia, cyanidric acid, phenol, and benzene, among others.  PLA is a corn-based polymer and is not exempt from dangerous emissions, especially if extruded at temperatures higher than 200°C.  Among the effects that the absorption of toxic VOC’s and nanoparticles can cause to humans, the most common are pulmonary pathologies, such as bronchitis, tracheitis, asthma. In some cases, these substances can also cause certain types of cancers, so this is not something to be taken lightly. [7]

Another problem with PLA is that , as one of the producers, Joe Selzer a vice president at Wilkinson Industries, puts it:  “I had my takeout box in my car in the sun and it melted into a pancake!” So PLA  can’t be used for such things as containers made for holding hot liquids.   He continues: “Our number-one concern is PLA’s competitive price, and then its applications. After that comes the feel-good.”  In the beginning, it cost $200 to make a pound of PLA, now it’s less than $1.[8]

PLA produces the greenhouse gas methane when it decomposes so composting isn’t a perfect disposal method.

But the biggest problem with PLA is it’s biodegradability:  PLA is said to decompose into carbon dioxide and water in a “controlled composting environment” in fewer than 90 days. What’s a controlled composting environment? Not your backyard bin.   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 has identified 113 such facilities nationwide—some handle industrial food-processing waste or yard trimmings, others are college or prison operations—but only about a quarter of them accept residential foodscraps collected by municipalities.

Moreover, PLA by the truckload may potentially pose a problem for some large-scale composters. Chris Choate, a composting expert at Norcal Waste Systems, headquartered in San Francisco, says large amounts of PLA can interfere with conventional composting because the polymer reverts into lactic acid, making the compost wetter and more acidic. “Microbes will consume the lactic acid, but they demand a lot of oxygen, and we’re having trouble providing enough,” he says. “Right now, PLA isn’t a problem,” because there’s so little of it, Choate says.  (NatureWorks disputes that idea, saying that PLA has no such effect on the composting processes.)

To plastic processors, PLA in tiny amounts is merely a nuisance. But in large amounts it can be an expensive hassle. In the recycling business, soda bottles, milk jugs and the like are collected and baled by materials recovery facilities, or MRFs (pronounced “murfs”). The MRFs sell the material to processors, which break down the plastic into pellets or flakes, which are, in turn, made into new products, such as carpeting, fiberfill, or containers for detergent or motor oil. Because PLA and PET mix about as well as oil and water, recyclers consider PLA a contaminant. They have to pay to sort it out and pay again to dispose of it.

Wild Oats accepts used PLA containers in half of its 80 stores. “We mix the PLA with produce and scraps from our juice bars and deliver it to an industrial composting facility,” says the company spokesman Sonja Tuitele. But at the Wild Oats stores that don’t take back PLA, customers are on their own, and they can’t be blamed if they feel deceived by PLA containers stamped “compostable.” Brinton, who has done extensive testing of PLA,says such containers are “unchanged” after six months in a home composting operation. For that reason, he considers the Wild Oats stamp, and their in-store signage touting PLA’s compostability, to be false advertising.[9]

Despite PLA’s potential as an environmentally friendly material, it seems clear that a great deal of corn packaging, probably the majority of it, will end up in landfills. And there’s no evidence it will break down there any faster or more thoroughly than PET or any other form of plastic. Glenn Johnston, manager of global regulatory affairs for NatureWorks, says that a PLA container dumped in a landfill will last “as long as a PET bottle.” No one knows for sure how long that is, but estimates range from 100 to 1,000 years.

Environmentalists have other objections to PLA. Lester Brown, president of the Earth Policy Institute, questions the morality of turning a foodstuff into packaging when so many people in the world are hungry. “Already we’re converting 12 percent of the U.S. grain harvest to ethanol,” he says. The USDA projects that figure will rise to 23 percent by 2014. “How much corn do we want to convert to nonfood products?” In addition, most of the corn that NatureWorks uses to make PLA resin is genetically modified to resist pests, and some environmentalists oppose the use of such crops, claiming they will contaminate conventional crops or disrupt local ecosystems. Other critics point to the steep environmental toll of industrially grown corn. The cultivation of corn uses more nitrogen fertilizer, more herbicides and more insecticides than any other U.S. crop; those practices contribute to soil erosion and water pollution when nitrogen runs off fields into streams and rivers.

Eric Lombardi, president of the Grassroots Recycling Network and a leader in the international Zero Waste movement, takes a nuanced view of PLA’s progress. He says it’s “visionary” even to think about biologically based plastic instead of a petroleum-based one. True, he says, there are problems with PLA, “but let’s not kill the good in pursuit of the perfect.”

So in the end, what have we learned?

  • It produces no toxic compounds when burned, unlike many plastics.
  • Like conventional plastic, it’s not likely to break down in a landfill.
  • It produces methane, a potent greenhouse gas.
  • Also like conventional plastic, it doesn’t break down quickly on land or in the ocean.
  • And finally, it only can be composted in commercial-grade composting plants, while failing to break down in a backyard compost pile.

Until the kinks are worked out on the disposal and reprocessing end, PLA may not be much better than the plain old plastic it’s designed to make obsolete.

 

[1]”Bioplastics Frequently Asked Questions.” European Bioplastics. June 2008. (Nov. 6, 2008)http://www.european-bioplastics.org/index.php?id=191

[2]https://science.howstuffworks.com/environmental/green-science/corn-plastic2.htm

[3] Royte, Elizabeth; Smithsonian Magazine, August 2006

[4] Wood, Shelby,  The Oregonian; posted October 27, 2008   https://www.oregonlive.com/environment/index.ssf/2008/10/pla_corn_plastic_problems.html

https://science.howstuffworks.com/environmental/green-science/corn-plastic2.htm

[6] Ibid.

[7] https://3dprintingindustry.com; accessed on 9.28.18

[8] Ibid.

[9] Ibid.

 

 

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