PLA is the most widely used bioplastic in the world. PLA or Polylactide (also known as Polylactic Acid, Lactic acid polymer) is a versatile commercial biodegradable thermoplastic based on lactic acid. Lactic acid monomers can be produced from 100% renewable resources, like corn and sugarbeets. Polylactide has been able to replace the conventional petroleum-based thermoplastics, thanks to the excellent combination of properties it possesses.
It is one of the most promising biopolymers used today and has a large number of application such as Healthcare and medical industry, Packaging, Automotive applications etc.
As compared to other biopolymers, PLA exhibits several benefits such as:
Eco-friendly – It is renewably-sourced, biodegradable, recyclable and compostable
Biocompatible – It is non-toxic
Processability – It has better thermal processability compared to poly(hydroxyl alkanoate) (PHA), poly(ethylene glycol) (PEG) and poly(?-caprolactone) (PCL)
Polylactides break down into nontoxic products during degradation and being biodegradable and biocompatible, reduce the amount of plastic waste.
But the most frequent question both of end users and converters of PLA is : what to do with PLA scrap?
PLA post consumer waste (packaging, tableware, cups, containers, 3D printed parts): what is the end-of-life of these products?
There are 3 options:
- plastic bin: PLA is recyclable thermoplastic and can be recycled if sorted from other collected plastics. The problem is that at the moment there aren’t efficient systems of sorting PLA from other plastics. Transfer stations that sort municipal solid waste have difficulties sorting mixed PLA and PET plastic streams, as they are both transparent. In case PLA contaminates waste streams of other plastics, buyers offer lower prices or are not interested in purchasing the recycled material at all. Since PLA is a relatively new polymer in the market, the associated volumes have not yet reached the critical mass required to sort PLA into a separate stream from post-consumer waste. In reality, many traditional polymers have also not yet reached a critical mass; PS, ABS, PC, PVC are also often not sorted and recycled.
- organic waste: There is confusion about the compost-ability and the bio-degradability of PLA. As PLA is made from renewable sources, such as starch (e.g. corn, potatoes, etc.), soy protein, cellulose, and lactic acid, it is compostable, but this process is only considered “composted” when 3 criteria are met:
- The material breaks down into carbon dioxide, water, and biomass.
- The PLA fully disintegrates
- No toxic residues are left and the compost supports plant growth
Biodegradable plastic is plastic that will degrade through the action of naturally occurring microorganisms, such as bacteria, fungi etc. over a period of time. Note that there is no requirement for leaving “no toxic residue“, as well as no requirement for the time it needs to take to biodegrade.
In an industrial composting facility, the complete composting process takes about 1 to 6 months, depending on (relatively high) temperature conditions and material type. The rate of composting PLA in industrial facilities is much higher in comparison to the composting rate of PLA at home. As an example, composting disposed PLA containers and cups take 1 – 3 month’s in an industrial facility, and it takes up to 6 month’s at home.
In addition, the compost of composters must be compliant with local regulations. In case the compost still contains PLA residues, the compost does not meet the regulation requirements. Therefore, many composters regard PLA as a “contaminant”, too.
- home composting: standard PLA is not compostable in home compost unless special additives are added to PLA to make it home compostable.
- undifferentiated waste: in case of undifferentiated waste, PLA scrap will go to:
- Landfilling: This bio-degradable material deserves a better end-of-life destination than a waste mountain.
- Or combustion: Combustion of PLA products yields energy, but waste can be burned only once. So, it is interesting to learn more about other end-of-life alternatives for PLA.
PLA post industrial scrap: how to recycle? If the PLA scrap of the production process is not contaminated by other polymers, PLA scrap is pretty recyclable by mechanical recycling. There are already several companies who are performing mechanical recycling of PLA waste, mainly from post-industrial or closed-loop environments.
Gianeco s.r.l. provides an excellent service to collect and increase value of PLA industrial scrap. Gianeco collects and recycle PLA from thermoforming process, flexible film, fiber in all forms (lumps, regrinds, flakes, bales, rolls). Then PLA scrap is grinded and pelletized to obtain the recycled PLA pellets for 3D printing, compounds and other applications.
The other way for recycling PLA scrap is chemical recycling.
Though PLA is a potential high volume raw material, there is no infrastructure for separately collecting and recycling PLA. Therefore, it often ends up in other conventional waste streams, thereby contaminating them and disturbing the state-of-the-art municipal recycling strategies.
The process of chemical recycling was developed as a part of the Fraunhofer Cluster of Excellence “Circular Plastics Economy CCPE®”. Six Fraunhofer institutes (Fraunhofer ICT, Fraunhofer UMSICHT, Fraunhofer LBF, Fraunhofer IML, Fraunhofer IAP and Fraunhofer IVV) are exploring ways for sustainable transformation of the entire plastic value chain to a circular economy.
Researchers have developed a strategy to chemically recycle post-consumer PLA waste into a lactate ester (ethyl lactate) which finds its commercial applications in chemical synthesis, magnetic tape coatings, plastic, metal, wood and food industry.
The process represents an economically and environmentally sustainable recycling strategy, capable of nearly completely depolymerizing the PLA substrate along with a high yield of ethyl lactate (80 %) in a relatively short period of time (< 20 min) and under mild reaction conditions (< 70 °C, ambient pressure).
An outstanding feature of this system is the use of a conventional and commercialized eco-friendly, organic catalyst. Another special feature of this process is the use of an eco-friendly, low-boiling solvent, capable of selectively dissolving the PLA fraction from a mixed plastic waste stream, consisting mainly of PET and PP.
This flexible process scheme is capable of handling virgin PLA of different grades (Total Corbion LX175 and NatureWorks™ PLA 6032 D) as well as post-consumer PLA cups. The process has been scaled up in 2019 from a laboratory scale to a technical scale (15 L) and its robustness was demonstrated by recycling post-consumer waste PLA cups, without any effect on the yield of the lactate ester.
The production of both PET and PLA is expected to increase by 2021, with the percentage increase of PLA being higher than that of PET. Due to its application, the estimated maximum contamination of PLA in waste PET streams could vary between 0.8 % to 8 % by 2021.
In such a scenario, innovative methods for removal of PLA would be required in order to assure high-quality recycled PET. In addition, the huge demand for PLA on the consumer market, coupled with high feedstock and energy demands for its production, is a major concern for the manufacturers of PLA.
With this strategy, adaptation of a circular economy approach for the synthesis of virgin-PLA would lead to approximately 50 % energy savings as compared to the conventional PLA production processes, starting from corn-cobs as feedstock.
Total Corbion PLA’s position is that mechanical and chemical recycling should become viable, economically feasible and commonly used end-of-life solutions for PLA-based products. Prime examples of relevant applications include trays, bottles and drinking cups. Total Corbion PLA is committed to developing the recycling value chain together with specialized PLA recycling companies to stimulate demand for rPLA, thereby increasing recycling rates for PLA-based products. Total Corbion PLA uses this paper as a platform to pose the open invitation for parties throughout the recycling value chain to collaborate together to close the loop for PLA recycling.
Chemical recycling, also known as feedstock recovery or tertiary recycling, is a process where plastics are converted into monomers, oligomers or hydrocarbons that can be used again to produce virgin polymers. There are two different forms of chemical recycling being investigated thermal depolymerization and chemical depolymerization. Thermal depolymerization, also known as cracking or pyrolysis, can be used for polyolefins like PE or PP. It is an energy intensive process that requires large, high-investment facilities to operate cost efficiently. Chemical depolymerization can be used for polyesters like PET and PLA. In the case of PLA, the chemical depolymerization process is a simple hydrolyzation which can be relatively easily performed in small scale facilities. Total Corbion PLA has the infrastructure in place to perform chemical depolymerization of PLA in its commercial plant in Thailand. This technology is already being used to internally recycle off-spec PLA products. Total Corbion PLA is currently investigating how to use this technology to chemically recycle post-industrial scrap from converters and post-consumer plastic waste.
Chemical recycling technologies can generate feedstock that can be used for production of virgingrade polymers, compliant with regulations similar to virgin polymers. It is Total Corbion PLA’s preference that these chemical recycling processes ‘plug in’ to our existing infrastructure in order to reduce cost and time-to-market. This is the reason that recycled feedstock will most likely not exist in physically separate flows, also called ‘identity preserved’ flows, and that they will instead be added together with the virgin raw materials in the manufacturing plant. To be able to account for the recycled input, Total Corbion PLA proposes to use the principles of mass balancing. Mass balancing is a well-known chain of custody approach that is already successfully implemented in, for instance, the FSC, BCI and BonSucro initiatives, where tracking identity preserved streams is costly and adds to the time-to-market. A mass balancing certification for chemical recycling is critical to enable the sale of certified recycled products down the value chain. Chemical recycling is technically possible, but not in commercial stage yet for post-consumer plastics.
Since 2004, NatureWorks has recycled more than 17 million pounds of off-grade Ingeo biopolymer at its Blair, Nebraska, manufacturing facility by applying a chemical process commonly used in the plastics industry called hydrolysis. During the hydrolysis process, Ingeo is broken down into its primary foundation, lactic acid. Following the hydrolysis process, the lactic acid is then converted back into Ingeo resin.
In the future, this process could be another option for the intentional lifecycle design of post consumer products made with Ingeo.
