What are bioplastics?
A bioplastic is a biobased polymer derived from biomass, and it may or may not be biodegradable. We refer to biobased plastics, i.e. industrial polymeric materials which are wholly or partly derived or composed of natural sources, including plants (such as corn, tapioca, or other forms of cellulose), animal and marine materials (for example, prawn shells) and its protein and chitin, bacteria and also fossil-fuel-based polymers. Bio-based sources or waste-based material solutions are compatible with a bio-economy, like materials derived from agriculture or food waste. Bagasse, for example, is a by-product of the sugarcane industry. It is what remains after crushing sugarcane stalks to extract their juice. It mainly consists of fibrous materials such as cellulose, hemicellulose, and lignin. Using this agro-waste diverts this biomass from incineration on fields.
Before discussing bioplastics and the relationship between biodegradability and compostability, it is necessary to define plastic.
“Plastics are a type of synthetic or manufactured polymer; similar in many ways to natural resins found in trees and other plants. Webster’s Dictionary defines polymers as: “any of various complex organic compounds produced by polymerisation, capable of being moulded, extruded, cast into various shapes and films, or drawn into filaments and then used as textile fibres.”
Bioplastics are a diverse family of materials with differing properties, of which there are three main groups
— Biobased (or partially biobased), durable (not biodegradable) plastics such as biobased polyethylene (PE), polyethylene terephthalate (PET) (so-called drop-in solutions), biobased technical performance polymers, such as numerous polyamides (PA), or (partly) biobased polyurethanes (PUR); (top left)
— Biobased and biodegradable, compostable plastics, such as polylactic acid (PLA), polyhydroxyalkanaoates (PHA), polybutylene succinate (BioPBS™), and starch blends (top right)
— Plastics based on fossil resources and biodegradable, such as PBAT and PCL, might be produced at least partly biobased in the future. (bottom right)
According to European Bioplastics (2018), a bio-based material “is defined as a bioplastic if it is either bio-based, biodegradable or both.
Classification of bioplastics according to The European Bioplastics Organization. Adapted from European Bioplastics, “What are bioplastics?”. https://docs.european-bioplastics.org/publications/fs/EuBP_FS_What_are_bioplastics.pdf (accessed 29/12/2022)
READ: READ: Materials shaping the future: Polymerised Lactic Acid (PLA)
What is biodegradation?
Biodegradation is a chemical process in which materials are metabolised to CO2, water, and biomass with the help of microorganisms. Effective biodegradation requires microorganism action that metabolises the material, significantly changing its chemical structure and converting it into other natural substances such as compost water and carbon dioxide. In the case of compostable materials, biotransformation happens in specific environmental conditions, including location, temperature, level of aeration, and timeframe, allowing microorganisms (especially by enzymatic action) to metabolise the material.
What are oxo-degradable plastics?
Oxo-degradable plastics are neither bioplastics nor biodegradable plastic but conventional plastics mixed with additives to imitate biodegradation.
Oxo-degradable plastics quickly fragment into smaller and smaller pieces, called microplastics, but don’t break down at the molecular or polymer level like biodegradable and compostable plastics. The resulting microplastics are left in the environment indefinitely. According to the ABA, products that do not meet the standards of bioplastics but only to ‘test methods’, for example, as the oxo-degradable, almost certainly do not and will not biodegrade in a composting facility in any desired time frame.
READ: European Bioplastics statement on oxo-degradable plastics
What is the difference between oxo-fragmentable and biodegradable plastics?
Here, we refer to the bottom right of the grid—biodegradable polymers derived from petrochemical chemistry. So-called ‘oxo-fragmentable’ products are made from conventional plastics and supplemented with specific additives to mimic biodegradation. In truth, however, these additives only facilitate fragmentation of the materials, which do not fully degrade but break down into tiny fragments that remain in the environment.
Biodegradability is an inherent characteristic of a material or polymer. In contrast to oxo-fragmentation, biodegradation results from the action of naturally occurring microorganisms. The process produces water, carbon dioxide, and biomass as end products. Oxo-fragmentable materials do not biodegrade under industrial composting conditions as defined in accepted standard specifications such as EN 13432, ISO 18606, or ASTM D6400 which is why these products are controversial.
Oxo-degradable (fragmentable) plastics are often marketed as ‘plant-based’, misleading the public into thinking they are compostable, leading to the contamination of organics collections. These products are incompatible with the bio and circular economy.
Biodegradability is a pre-requisite to compostability
To be recovered for organic recycling (composting) a material or product needs to be biodegradable.
Biodegradability can be confirmed by certification to various internationally recognised standards such as EN 13432, ASTM D6400, or in Australia, AS 4736-2006, where biodegradability in commercial composting facilities is required. Biodegradability is not affected by the source of the raw material, so fossil-based raw materials can be biodegradable, just as some renewable raw materials can be.
Compostability is characteristic of a material packaging product that allows it to biodegrade under specific conditions (e.g. a certain temperature, timeframe, etc) as described in standards, such as the Australian Standard on Commercial Composting AS4736 and Home Composting AS5810-2010. Materials and products complying with this standard can be certified and labelled accordingly.
DIN CERTCO is the certification body of TÜV Rheinland Group. TÜV Austria and DIN CERTCO are certification bodies internationally recognised to deliver compostability certification (e.g. home OK compost logo, industrial TUV compostable logo).
All Australian tests are carried out in accordance with and are based on EN 13432 standards and other international standards above, classified as 'equivalent'. The Seedling logo is a registered trademark owned by European Bioplastics and administered by the Australasian Bioplastics Association (ABA) in Australia. It proves that the product’s claims of biodegradability and compostability as per Australian Standards have been tested (Australasian Bioplastics, 2017).
A material is considered compostable when, under defined conditions in a composting system the material is:
1) entirely transformed to minerals and biomass within a specified time period and
2) its decay results in compost, a natural fertiliser that can help to restore soils, control weeds, retain ground moisture, and reduce soil erosion.
READ: Ministry for the Environment compostable products publications
Identifying bioplastics
Currently, bioplastics and biodegradable plastics are identified by the ASTM International Resin Identification Coding System as part of group 7 or ‘other’ (Figure 21b), an identification system developed by the Society of the Plastics Industry in 1988 and administered by ASTM International since 2008. Polymers included in group 7 do not have specified characteristics, and their management process is not defined.
Currently it is difficult to identify certified compostable packaging from non-compostable, non-biodegradable and recyclable products. A solution to this problem would be to globalise a symbol easily identifiable, identifying polymers classified as compostable or biodegradable according to proper standards, such as ASTM D6400, ASTM D6868, EN 13432, ISO 17088, ASTM D5338 and ASTM D5929.
For example, the European Bioplastics created the Seeding logo (Figure 21a) as a label to identify compostable polymers according to the EN 13432 standard. Usually, this label goes along with one other created by Vinçotte (taken over by TÜV AUSTRIA Group), the “OK compost home“, “OK compost industrial“, “OK marine biodegradable“, “OK soil biodegradable“, “OK water biodegradable“ and “OK biobased“ (Figure 21c), because these should guarantee complete biodegradability in the specified requirements.
Figure 21. Labels currently used as compost, biobased and biodegradable polymers by European Bioplastics (a), ASTM International (b) and the Vinçotte/TÜV AUSTRIA Group (c) [32,73,81].
Source: Costa, A.; Encarnação, T.; Tavares, R.; Todo Bom, T.; Mateus, A. Bioplastics: Innovation for Green Transition. Polymers 2023, 15, 517. https://doi.org/10.3390/ Polym15030517
Accurately communicating end of life
In the global market today, there are many offerings of derivative plastics claiming to be biodegradable and compostable. Biobased and non-biodegradable plastics still represent approximately 35.8% of the global bioplastic production capacities.
Transparency is required so that business owners and people in procurement positions have the available and accurate information to make an informed decision. Identifying the ‘disposal environment’ is vital when discussing or reporting the biodegradability of a product, e.g., biodegradability in a composting environment (compostable plastic), biodegradability in a soil environment, biodegradability under anaerobic conditions (in an anaerobic digester environment or even a landfill environment) or biodegradability in a marine environment for example.
READ: WasteMINZ Best Practice Guidelines for Advertising Compostable Packaging
Bioplastics Market Development Update 2021”. https://docs.european-bioplastics.org/publications/market_data/Report_Bioplastics_Market_Data_2021_short_version.pdf
Future potential for compostable bioplastics
Compostable bioplastics currently represent only 1% of the plastics produced globally. They are materials with great potential for development. And while not yet used industrially on a large scale, the environmental and ecological advantages of using compared to petrochmial based plastics are immense. Less chemical pollution, less energy consumption and less CO2 emissions are some primary drivers of a transition to a circular economy using biodegradable and compostable bioplastics.
Costly production and and limited end-of-life (organic recycling) due to market size and recoverability options will be overcome in time with continued investment as the market grows and the need to divert food waste from landfill becomes more urgent in response to public pressure to restrict town landfill growth.
Not all biobased plastics are bio-degradable and compostable. As bioplastics continue to become a popular alternative and in the absence of regulation, being clear about the materials and what you are buying is vital to avoid misrepresenting your sustainability efforts.
Are you ready to remove non-renewable materials from your business?
To reach net zero faster, and to create a thriving tomorrow that is sees council invest in composts and less landfill, it is essential to share information about bioplastics to our customers, composters, local government and the general public to prove that compostable bioplatics are a very viable solution to the plastic pollution problem associated with single-use petrochemical based packaging and products.
We know it can be challenging to transition away from your current products which is why we work with you to translate your existing packaging to a petrochemical-free solutions. Email us at hello@ecoware.co.nz and we will work with you to transition seamlessly.
