Biodegradable plastics are gaining popularity in the industry. This is majorly due to their ability to address the environmental concerns posed by traditional plastics. Their major significance includes:
- mitigating the environmental impact of plastic wastes
- reducing plastic pollution
- aligning with sustainable practices
- complying with the regulatory standards
Despite these benefits, there are a few challenges faced while using biodegradable plastics. One of them is the variability in environmental conditions for decomposition. The other factors are the lack of awareness about the right disposal method and the lack of compatibility with the existing systems of waste disposal.
However, adopting the universally accepted standards for polymers that are biodegradable helps overcome these challenges. Also, public education and infrastructure developments will help to better navigate these challenges.
| Sustainability Path #1 — Use Materials of Bio-based Origin |
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Get in-depth knowledge about:
- Biodegradability in Plastics — Mechanism and Key Features
- What are the types of biodegradable plastics?
- Do biodegradable polymers align with the sustainability aspects of plastics?
- Which test methods measure the biodegradability of plastics?
- Is the polymer of your interest biodegradable?
Biodegradability in Plastics — Mechanism and Key Features
Biodegradable plastic was invented by a French microbiologist, Maurice Lemoigne in 1926. He found that a bacterium called
Bacillus megaterium could produce a biodegradable plastic called polyhydroxybutyrate (PHB). However, they were only commercialized by the 1980s, when scientists developed a way to produce PHB from corn starch.
Biodegradable plastics can be degraded by microorganisms present in the environment. They do so by entering the microbial food chain. This property is not dependent on the origin of the raw materials. It is dependent only on the chemical composition of the polymers.
The biodegradation of plastics is not a uniform process. This is because the disposal conditions vary dramatically from one place to another. The biodegradation of polymers can be tailored specifically for controlled degradation. This can take place under the inherent environmental stress in biological systems either unaided or by enzyme-assisted mechanisms.
Biodegradation is the property of a material that can be converted entirely into CO
2, water, and biomass. This happens by the action of microorganisms such as fungi and bacteria.
Where:
- Cpolymer is the carbon of the polymer
- O2 is oxygen
- CO2 is carbon dioxide
- H2O is water
- Cbiomass is biomass
Mechanism of degradation of plastics
In general,
biodegradable polymers break down to form gases, salts, and biomass. Complete biodegradation occurs when there are no oligomers or monomers left. The breakdown of these polymers depends on the polymer and the environment the polymer is in. The two primary mechanisms by which biodegradation can occur are as follows:
- Physical decomposition — This takes place through reactions such as hydrolysis and photodegradation. This can lead to partial or complete degradation.
- Biological decomposition — This process can be further divided into aerobic and anaerobic processes.
➤ Aerobic biodegradation takes place in the presence of oxygen: Cpolymer + O2 → Cresidue + Cbiomass + CO2 + H2O
➤ Anaerobic biodegradation happens in the absence of oxygen: Cpolymer → Cresidue + Cbiomass + CO2 + CH4 + H2O
In the above equations:
- Cresidue are the smaller fragments of the initial polymer such as oligomers
- Cpolymer is the carbon of the polymer
- O2 is oxygen
- CO2 is carbon dioxide
- H2O is water
- Cbiomass is biomass
Properties of biodegradable plastics
✓ All biodegradable polymers must be easily broken down upon their disposal.
✓ They have extremely strong carbon backbones. Hence their process of degradation gets started from their end-groups.
✓ They have a high surface area. This allows easy access for chemicals, light, and organisms to cause degradation.
✓ A low degree of polymerization is common in these polymers. This allows the end groups to be more accessible for reaction with the degradation initiator.
✓ They are hydrophilic in nature due to the presence of polar functional groups. This enables their easy degradation by microorganisms.
What are the types of biodegradable plastics?
Based on structure
Biodegradable polymers consist of ester, amide, or ether bonds. Based on their structure and synthesis, biodegradable polymers can be grouped into two large groups:
Based on the mechanism of degradation
| Oxo-biodegradable Plastic (OBP) |
Hydro-biodegradable Plastic (HBP) |
| Made by adding a small portion of fatty acid compounds of specific transition metals to traditional plastics |
Made from bio-based sources such as corn, wheat, sugarcane, petroleum-based sources, or a blend of the two |
| Undergoes chemical degradation by oxidation which is then followed by a biological process |
Undergoes chemical degradation by hydrolysis which is then followed by a biological process |
| Degrades by oxidative chain scission catalyzed by the metal salts, leading to the production of shorter chain molecules. In oxygen-containing environments, plastics containing oxo-degradation additives will degrade and fragment. Fragments that are smaller and have lower molecular weight are conducive to biodegradation. They emit CO2 upon degradation over a longer time frame |
They can emit CO2 as well as methane upon degradation. Degrades and biodegrades more quickly than OBP |
Claims biodegradability according to:
- ASTM D5988
- ASTM D6954-04 standards conducted by independent laboratories like, Smithers-RAPRA (US/UK), Pyxis (UK), and Applus (Spain)
Does not claim to meet compostability standards.
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Meets the following standards:
- ASTM D6400-04
- EN 13432 (developed for compostability)
Quoted standards relate to the performance of plastics in a commercially managed compost facility and are not biodegradation standards |
| Both these types are compostable, but only OBP can be recycled.
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Commercial selection of biodegradable plastics
Other polymers that can be biodegradable are based on
natural fiber, bacteria, and lignin.
Do biodegradable polymers align with the sustainability aspects of plastics?
Biodegradable vs. compostable plastics – How are they different?
Compostable is always biodegradable, but biodegradable is not always compostable
Biodegradable and compostable represent the organic materials breaking down in a specific environment. Both terms are often used when defining environmentally friendly products. However, they are often misused.
The main difference between compostable and biodegradable is:
- Compostable plastics are biodegradable in composting conditions
- Other plastics degrade in the soil, for example, in landfills or anaerobic digestors
It is important to note that compostability is a characteristic of a product, packaging, or associated component. They allow it to biodegrade under specific conditions (for example, at a certain temperature, timeframe, etc.).
Can all biodegradable plastics be recycled?
Theoretically, biodegradable polymers can be recycled. But they are not currently recycled on a large scale because:
- Biodegradable polymers are often mixed with other materials, like food scraps and paper, in waste streams. This makes it difficult to separate the biodegradable polymers from the other materials.
- Biodegradable polymers can degrade during the recycling process. This can lead to reduction in quality of the recycled material.
- There is a lack of infrastructure for recycling biodegradable polymers.
However, there is growing interest in recycling biodegradable polymers. New technologies are being developed to separate these polymers from other materials in waste streams. New recycling processes are being developed that are specifically designed for biodegradable polymers.
Some biodegradable polymers, such as
polylactic acid (PLA) can be recycled at home. PLA can be composted in a backyard compost bin or sent to a commercial composting facility.
How is the mass balance approach relevant for biodegradable plastics?
In the context of biodegradable plastics, the mass balance approach can be used to:
- Increase the biobased content of biodegradable plastics. By using a mass balance approach, manufacturers can mix renewable and fossil-based feedstocks. This enables the production of these polymers with a higher biobased content.
- Track the flow of renewable materials through the supply chain. The mass balance approach ensures that the renewable materials used to produce biodegradable plastics are actually used to make those plastics. It confirms that they are not diverted to other uses.
- Provide consumers with information about the biobased content of polymers that biodegrade. The mass balance approach enables the manufacturers to certify their biodegradable plastics. This indicates the percentage of biobased content.
The
mass balance approach helps to increase the sustainability of biodegradable plastics. It reduces the reliance on fossil-based feedstocks, reduces greenhouse gas emissions, and creates a more circular economy for plastics.
Are they good or bad for the environment?
| Advantages |
Disadvantages |
- As biodegradable plastics are made from renewable resources, they help to reduce the dependence on petroleum, a non-renewable resource.
- They can break down naturally in the environment. This helps to reduce plastic pollution in landfills and oceans.
- They can be composted, which produces nutrient-rich soil that can be used to grow plants.
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- Biodegradable plastics can take longer to break down than traditional plastics, especially in environments with low temperatures or low oxygen levels.
- They can fragment into microplastics, which can pollute the environment and harm wildlife.
- Some of them contain additives that can be harmful to the environment.
- There is a lack of infrastructure for composting biodegradable plastics in many areas.
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Which test methods measure the biodegradability of plastics?
ASTM D6400
This method specifies the labeling of plastics designed for aerobic composting. Such composting takes place in municipal or industrial facilities. This specification determines the satisfactory composting of end items in large-scale aerobic municipal or industrial composting facilities. This includes packaging, which uses plastics and polymers as coatings or binders. Maximum throughput is a high priority for composters. The intermediate stages of plastic disintegration and biodegradation are not visible to the end user. This is due to the aesthetic reasons.
EN 13432
It specifies the requirements for packaging recoverable through composting and biodegradation. It also gives a view of the test scheme and evaluation criteria for the
final acceptance of packaging.
The certification confirms the product to be industrially composted. It also ensures that not only the plastic but also all other components of the product are compostable. For example, colors, labels, glues, and in the case of packaging products, residues of the content.
For other plastic items such as organic waste bags and agricultural mulch films, the equivalent standard is BS EN14995.
ISO 17088
It provides specifications for compostable plastics. It specifies procedures and requirements for the identification and labeling of plastics. It also provides information on plastic products that are suitable for recovery through aerobic composting.
There are four aspects that are addressed. They are:
- Biodegradation
- Disintegration during composting
- Negative effects on the composting process and facility
- Negative effects on the quality of the resulting compost. This includes the presence of high levels of regulated metals and other harmful components
This specification establishes the requirements for the labeling of plastic products and materials. This includes packaging made from plastics, as “compostable” “compostable in municipal and industrial composting facilities,” or “biodegradable during composting”.
Watch Course: Ease your biodegradable & compostable packaging compliance.
DIN CERTCO
DIN CERTCO's certifications are in accordance with European or international standards. This test mark is globally recognized. It proves that the bioplastic has been tested and conformity confirmed by an external, independent, and qualified body. DIN CERTCO is the only accredited certification body for environmental certifications at the EU level
1.
JPBA's BiodegradablePla certification
Japan BioPlastics Association (JBPA) keeps a close cooperation basis with the US (BPI), EU (European Bioplastics), China (BMG), and Korea
2. It has continued discussions with them about various technical items including:
- the analytical method to evaluate the biodegradability,
- the product specifications,
- the recognition and labeling system, etc.
JBPA has a certification system for biodegradable plastic (BiodegradablePla) products
2.
Is the polymer of your interest biodegradable?
Click to find polymer you are looking for:
A-C |
E-PP |
PS-X
| Polymer Name |
Yes/No |
| Bio Polyether Block Amide, PEBA (28-32%renewable carbon) |
No |
| Bio PEBA (44-48% renewable carbon) |
No |
| Bio PEBA (62-66% renewable carbon) |
No |
| Bio PEBA (77-81% renewable carbon) |
No |
| Bio PEBA (87-91% renewable carbon) |
No |
| Bio PEBA (93-97% renewable carbon) |
No |
| Bio-TPU 85 Shore A |
No |
| Bio-TPU 90 Shore A |
No |
| Bio-TPU 95 Shore A |
No |
| CA - Cellulose Acetate |
No |
| CAB - Cellulose Acetate Butyrate |
No |
| CP - Cellulose Propionate |
No |
| PA 10.10-Unreinforced |
No |
| PA 11 - (Polyamide 11) 30% Glass fiber reinforced |
No |
| PA 11, Conductive |
No |
| PA 11, Flexible |
No |
| PA 11, glass filled |
No |
| PA 11, Rigid |
No |
| PC/PLA(25%) blend |
No |
| PC/PLA(40%)blend |
No |
| PCL - Polycaprolactone |
Yes |
| PE/TPS Blend - Polyethylene/Thermoplastic Starch |
No |
| PGA - Polyglycolides |
Yes |
| PHB - Polyhydroxybutyrate |
Yes |
| Poly(hydroxybutyrate - co- valerate) PHB-V(5% valerate) |
Yes |
| PLA - Polylactide, Fiber Melt Spinning |
Yes |
| PLA, Heat Seal Layer |
Yes |
| PLA, High Heat Films |
Yes |
| PLA,injection molding |
Yes |
| PLA, Spunbond |
Yes |
| PLA, Stretch blow molded bottles |
Yes |
| TPS/biodegradable copolyester |
No |
| TPS/PP BLend - Thermoplastic Starch/ Polypropylene |
No |
| TPS, Injection General Purpose
|
Yes |
| TPS, Injection Water Resistant
|
Yes |
References
- https://www.dincertco.de/din-certco/en/
- http://www.jbpaweb.net/english/index.html