Polylactic Acid: A Sustainable Bioplastics Packaging Option
23 Aug, 2018
23 Aug, 2018
In recent years, one packaging solution touted as a ‘sustainable’ option that has been emerging in Asia is Bioplastics and biodegradable and/or compostable packaging. But what exactly are Bioplastics and what does it mean when a company says its products are biodegradable and/or compostable?
What are Bioplastics?
There are many definitions for bioplastics, but essentially, a bioplastic is a plastic material that is either derived from biological raw materials (known as being biobased), or biodegradable, or both.
As with all sustainability issues, there is some debate over which type of bioplastic is the most sustainable. Generally though, the most sustainable type of bioplastic is the one that is both biobased (sustainable front-of-pipe material source) and biodegradable (environmentally-friendly waste management at end-of-pipe).
Biological raw materials are derived from biomass, such as corn, sugarcane, cassava, vegetable fats and oil, agricultural waste etc. Biomass is renewable, because it is of agricultural/bio-based origin.
It doesn’t really matter what the plant source is; what is needed is the sugars from the plant. Through the process of photosynthesis, every plant converts carbon from CO2 in the atmosphere () as it grows, into materials such as lignin, cellulosic, and simple or complex sugars (e.g. starch).
While the manufacturing process for bio-based plastics may differ slightly from one to another manufacturer – mainly in relation to the biomass source - but the science is similar.
For example, NatureWorks LLC produces its PLA bioplastics, branded as ‘Ingeo’, from dextrose, a sugar derived from the starch in corn that has been grown for many industrial and functional applications. In production, the sugar is converted by microorganisms through fermentation into lactic acid. The lactic acid molecules then combine to first form lactide rings, which link up to form long chains of polylactide polymer (PLA) – this process is known as polymerization.
The Ingeo bioplastic pellets are converted into a wide range of commercial products, including fibers, rigid and flexible packaging, and durable products.
What does it mean when we say a bioplastics is biodegradable?
Biodegradation is a type of decomposition process in which naturally-occurring micro-organisms that are available in the environment convert material into natural substances: water, carbon dioxide and biomass. In other words, biodegradation is decomposition by biological means.
A bioplastic can be biodegradable, or not, depending on its raw materials source, the manufacturing process, and its intended application.
Even then, a material can only be termed as “biodegradable” if it meets specific conditions and timeframe under which the degradation or decomposition process takes place. The conditions – governing industrial composting, marine water or soil degradation - and timeframe are clearly defined by legislative standards.
How do we ensure a bioplastics is what it claims to be?
For manufacturers sourcing bioplastics for conversion, and for consumers examining products for purchase at retail, it is important to check that the correct certification and labels are presented.
In parts of Asia, there are currently no legislative standards for bioplastics certification. So the best way to ensure the authenticity of the bioplastic is to refer to the European CEN standards, or ISO and the ASTM standards.
Here’s a partial listing of the standards to check for:
Biobased mass content:
a. CEN/TS 16137
b. ASTM 6866
EN 13432 and EN 14995: These are technically identical in their requirements. EN 13432 is specific to packaging material only. EN 14995 is more broad in its coverage; it can cover packaging as well as non-packaging applications)
D6400-12 : “Standard Specification for Labeling of Plastics Designed to be Aerobically Composted in Municipal or Industrial Facilities”. This standard specification covers all plastics and products made from plastics; there is no distinction of packaging or other plastic products (bags) as there is with EN 13432 and EN 14995. D6400 is for solely plastic items; it is not for plastic coated items this would be covered by
D6868-11 : “Standard Specification for Labeling of End Items that incorporate Plastics and Polymers as Coatings or Additives with Paper and Other Substrates Designed to be Aerobically Composted in Municipal or Industrial Facilities”. D6868 covers coated paper plates or bagasse products
b. ISO 17088 -12 : “Specifications for compostable plastics”
c. ISO 18606-13 : This standard is for packaging suitable for organic recycling.
Ideally, a bioplastic product should have certification that covers any aspect of its lifecycle around which marketing claims are being made – from its biobased content and source, production, and end-of-life.
Ingeo for instance, has biobased content certification vertifying that 100% of the carbon in the Ingeo biopolymer originates from renewable agricultural resources, from Vincotte based in Belgium, Europe, and the United States Department of Agriculture (USDA)’s BioPreferred program.
To ensure that its raw material sources are being produced sustainably and have proper chain of custody, NatureWorks sources from farmers that are audited and certified under the International Sustainability & Carbon Certification (ISCC) or Working Landscape Certificates (WLC) schemes. Ingeo is also Cradle to Cradle Certified Silver by the Cradle to Cradle Products Innovation Institute.
Where certification for composting is concerned, most of the Ingeo grades supplied from NatureWorks have BPI (Biodegradable Products Institute) certification for ASTM D 6400, and DIN CERTCO certification according to EN 13432. Producer NatureWorks is quick to point out however, that final products made from its resins must be certified in their finished form, and emphasizes that marketing claims of product compostability are often irrelevant. It does not support such claims unless Ingeo based products have a role in diverting organics from landfill (e.g. foodserviceware, or bag applications).
For food safety, Ingeo is compliant with a number of food contact regulations around the globe, including the US and Europe, Australia, Japan, Korea, Mexico, New Zealand, China and Taiwan.
Because of the ever-increasing amount of plastic wastes worldwide considerable research and development efforts have been devoted towards making a single-use, biodegradable substitute of conventional thermoplastics. Biodegradable polymers are classified as a family of polymers that will degrade completely - either into the corresponding monomers or into products, which are otherwise part of nature, through metabolic action of living organisms.
They should offer a possible alternative to traditional, non-degradable polymers as the recycling of the latter is impractical or hazardous to the environment or not economical. Headway is being made with a polymer called Polylactic Acid (PLA), an affordable, recyclable, innovative packaging material made from renewable resources.
The lactic acid used to make it is derived from corn. The process used to make it involves both biotechnology and chemistry. Poly(lactic acid) (PLA) belongs to the family of aliphatic polyesters commonly made from –hydroxyl acids, which include polyglycolic acid or polymandelic acid, and are considered biodegradable and compostable. PLA is a thermoplastic, high-strength, high-modulus polymer that can be made from annually renewable resources to yield articles for use in either the industrial packaging field or the bio-compatible/bio-absorbable medical device market.
Lactide the monomer of polylactic acid which is obtained from 100% naturally renewably resourced. It is mostly removed by using plant sugars from field corn as the source material for manufacturing. Monomer of polylactic acid uses less than 1/20th of 1% (0.05%) of the annual global corn crop today, and as such contributes little to no impact on international or local food chains. It doesn’t require corn, it only needs a sugar source. Alternative sugar sources for lactic acids are Sugar beet, Tapioca, Sugar cane and wheat are 100% renewable resources and available in plenty and cheaply. Then preparation of lactic acid is done by fermentation broth of sugar and starch using different lactic acid bacteria (LAB), exists almost exclusively as the dextrorotatory (D or L(+)) form for producing i.e polymerization of PLA which is carried out in three different methods (i) Condensation of Lactic acid (ii) Solid state polymerization and (iii) Ring opening polymerization.
Comparison with other Polymers
Comparision with PET
1. Belong to Polyester family.
2. Both polymers need to be dried before melting to avoid hydrolysis, both polymers readily form fibers via melt extrusion, and fibers from both polymers can be drawn (stretched) to develop useful tensile strength.
1. Opposite Polarity.
2. PLA’s is obtained from vegetable source hence is a Aliphatic compound as opposed to PET’s mineral or fossil fuel source which is Aromatic compound.
3. PET chain is nominally linear, while the PLA molecule tends to assume a helical structure.
Grades of PLA
There are a number of PLA grades depending upon viscosity and crystallization are their primary differentiators that are available for commercial customers which can be used for a number of different applications.
PLA is poised to play a big role as a viable, biodegradable replacement. PLA provides the opportunity for economically viable, true closed-loop, cradle -to-cradle solutions.
Cereplast – High heat resistant PLA
Cereplast's high heat resistant polymer compositions can be compostable and can preserve their structural characteristics at temperatures higher than 74°C.Cereplast's sustainable bio-plastics are used as alternatives to traditional plastics in major converting processes such as extrusions, blow molding, thermoforming and injection molding. Cereplast Compostables resins are suitable for single-use applications which mainly require high biobased content and compostability, particularly in the food service sector.
Michigan State University: Micro perforated PLA packaging system.
Michigan State University’s microperforated PLA packaging system is a bio-based, environmentally advantageous system for packaging fresh produce. The invention enables even greater shelf-life extension than standard petroleum-based microperforated systems. The improved and environmentally advantageous system is used to make semi-rigid containers with microperforated flexible lids and microperforated flexible pouches. The technology is specifically applicable where equilibrium modified atmosphere packaging (EMAP) and modified atmosphere packaging (MAP) systems are employed.
Biopolymer Network: E-PLA Foams
Biopolymer Network has a patent application for a new method of producing E-PLA bio-foams from commercially available PLA beads using a novel CO2 foaming technology. This technology can be used to produce both foamed beads and moulded shapes and products such as insulation, packaging and speciality components. The foam is both sustainably sourced and can be disposed of through industrial composting.
Inexpensive meat freshness indicator for packaging monitors actual spoilage, not just refrigeration continuity
The Fresh Stripe freshness indicator for meats is a multi-layer polymer indicator. The indicator polymer can be polylactic acid PLA, polylactic-L acid PLLA or poly(lactic-co-glycolic acid) PLGA. The polymer layer biodegrades at a predictable rate in the presence of the same hydrolytic bacterial enzymes that degrade meat. Freezing, refrigeration, and heat do not degrade the performance of the indicator or affect its accuracy It is important for the sensor always to have contact with meat juices and to be visible to the naked eye at the same time.
Wal-Mart- Retail chain
For a few years, natural foods purveyors such as Newman’s Own Organics and Wild Oats have been quietly using some PLA products, but the material got its biggest boost when Wal-Mart, the world’s largest retailer, announced that it would sell some produce in PLA containers Wal-Mart plans to use 114 million PLA containers a year, which company executives estimate will save 800,000 barrels of oil annually
Iper – PLA replaces HIPS
Iper a food retailer in Milan, Italy, has adopted PLA in place of HIPS for a line of short-shelf-life hinged containers for fresh salad, fruit, and pasta. One motive is to market a "natural" product in a "natural" package. PLA is also breathable, which improves freshness and reduces fogging. Equally important is PLA's superior appearance and potential for down gauging versus HIPS, along with its ability to run on existing extrusion lines and tools.
Starbucks Talks Sustainability
Starbucks is working with ConAgra Foods to make their coffee cups recyclable. Conagra Foods are different in that they use postindustrial recycled polylactic acid and convert it into shrink film packaging materials (i.e. the inside lining of Starbucks coffee cups to increased thermal stability)). The company's PLA shrink film contains more than 50% post-industrial recycled material, and it uses this material for tamper-evident seals on some of ConAgra Foods' table spreads. By collaborating with its suppliers, Conagra has been able to convert 260,000 pounds of resin from non-renewable resources (PVC and PET g) to PLA.
Dow chemical company: Additives for semi- durable packaging.
The Dow Chemical Company has a long tradition of innovation and commitment to bringing market-responsive products to the packaging industry. Dow developed PARALOID™ BPM-500 which gives an excellent balance of impact performance delivers excellent colorability, exceptional surface finish and high impact strength at room and sub-zero temperatures. Its modifier is a versatile PLA additive solution for opaque food and semi-durable packaging applications.
Frito-Lay: Why PLA is so Noisy
2010 Frito-Lay introduced a 100% compostable bag for its SunChips. Consumers complained that handling the bags made a sound like a screeching train and irritated customers. Their sales declined by some 11% due to the 95 decibel eardrum-blasting crinkle, From the beginning the company realized that there was a noise issue. The problem has to do with the “glass transition temperature ( Tg),” which is the temperature at which a plastic transforms from a hard, glass-like state to a flexible, rubbery state. Polylactic acid has a glass transition temperature that is just above room temperature so that just handling the bag is enough to cause the disturbing crinkling as the polymer oscillates between flexibility and brittleness. The PLA bag, although only 20 micrometers thick, is actually made of multiple layers that include PLA, aluminum and a sealant held together by an adhesive. It seems that using a rubbery adhesive between the bag’s layers can cut the crinkling sound to an acceptable 70 decibels.
Danone: Converting some yogurt packaging to PLA
Global food giant Groupe Danone has converted about 5 percent of its yogurt packaging to bio-based polylactic acid. PLA is currently used as a replacement for high impact. The interest in PLA for rigid packaging which offers PLA in horizontal form-fill seal packaging it would be a marketing angle for consumers interested in buying a “green” product.Today, PLA also is starting to offer a more competitive financial prospect. On a price per pound basis, PS is still cheaper, but because PLA packaging can be produced with a thinner wall and takes less space in shipping, it can be the same in a price per piece as packages can be produced using PLA that are 27 mils thick, compared to 36 mils for PS.
Hair O’right and Capardoni & C srl – Cosmetic Eco-packaging.
The world’s first shampoo bottle from plant-based polylactic acid plastic was a natural one. PLA shampoo bottle, which Hair O’right claims is the first globally, as bringing its packaging more in line with its environmental goals. Hair O'right plans to use PLA for all its new products, rather than the petrochemical-based HDPE bottles.
BASF has introduced PLA its first biodegradable plastic based on a renewable raw material.
BASF Corp., Florham Park, N.J., had introduced its first biodegradable plastic based on a renewable raw material. Ecovio contains 45% polylactic acid (PLA) from NatureWorks LLC, blended with BASF's Ecoflex biodegradable polyester, which is derived from petrochemicals. The first application will be films for shopping bags. Ecovio is made by a special process that chemically binds Ecoflex and PLA. The material can be extruded into film as is or mixed with Ecoflex or PLA to obtain softer or harder formulations for injection molding or deep-draw applications.
Currently PLA covers approximately 10-15 percent of the total plastics market. Limited Fossil Fuel Resources, rising petrochemical prices, Reinforcement of PLA with other materials, environmental safety awareness and government incentives will be key factors driving the PLA market. Reinforcement of PLA with other materials creates huge opportunities for future. As natural fibers are low cost and degradable, it’s reinforcement with PLA leads to a material which is economical as well as ecological. The global PLA market is expected to reach a market size of 5.2 Billion USD, growing at a CAGR of 21.6 % during 2013 to 2020. By 2020, the market share of PLA is projected to increase to 25-30 percent
In the global market, the production capacity of PLA and the market demand increases but its price is on the decline. Price of PLA have reduced from original level of USD 1.50 per lb in the early 2000‘s to currently USD 0.85 per lb or lower, making PLA competitive with materials such as PET which cost about USD 0.65 per lb. The cost compared to regular plastic products is becoming more competitive as the interest in biodegradable product rises. Also costs of PLA may not fluctuate as much as petroleum-based resins as it is made from corn instead of petrochemicals and hence insulated from volatile and rising petroleum prices. In general, for a well-developed Polylactic acid industry and to further bring down the cost, the factors such as expanding the production scale, improving the properties of PLA and support from the government will prove to be vital.
The modern business world is being driven by the need to reduce its environmental footprint i.e sustainability while also controlling costs. Fortunately, it is possible to achieve both goals, as the increasing popularity of Polylactic Acid (PLA) Packaging technology demonstrates.
Poly Lactic Acid (PLA) in packaging has a number of advantages over Petrochemical based polymers such as being biodegradable as its obtained from 100% natural sources, reduce green-house gas emissions, lower Carbon footprint, ease in manipulating structure-property-processing relation, etc.
Transitioning to PLA packaging materials will become increasingly important as governments, other businesses, and the public become more concerned with environmentally friendly policies. That along with reducing cost makes PLA a win-win. It is extremely likely that PLA packaging will continue to increase in importance, eventually displacing polystyrene-based materials, and also other materials for most packaging applications.
1. Various internet resources like Linked-In Posts, company websites.
2. Review paper by Deepika Salaskar, Erstwhile PG student at SIES School of Packaging
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