What are bioplastics?

Bioplastics are a broad category of plastic materials that may be bio-based, biodegradable, or both. While many people assume all bioplastics are made from plants and will naturally biodegrade, the term encompasses a much wider range of materials with different properties and end-of-life pathways. Bioplastics may be produced wholly or partly from renewable biological resources such as corn starch, sugarcane, cellulose, algae, bacteria or agricultural by-products. Others are biodegradable but manufactured using fossil-based feedstocks. Whether a material is bio-based does not determine whether it is biodegradable or compostable, which is why recognised certification and end-of-life standards are so important. 

Before exploring the different categories of bioplastics, it is helpful to understand what plastic actually is.

Plastics are materials made from polymers—long chains of molecules that can be moulded into a wide variety of products. Traditionally, most plastics have been manufactured from fossil fuels such as oil and natural gas. Bioplastics differ because they may be produced from renewable biological resources, designed to biodegrade under specific conditions, or both.

Understanding the different types of bioplastics

Bioplastics are generally grouped according to whether they are bio-based, biodegradable, or both. Understanding these categories is important because they determine how a material behaves at the end of its life.

Biobased (or partially biobased), durable (not biodegradable) plastics

Materials 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

These materials are produced from renewable resources and are designed to biodegrade under appropriate conditions and include polylactic acid (PLA), polyhydroxyalkanaoates (PHA), polybutylene succinate (BioPBS™), and starch blends (top right).

Plastics based on fossil resources and biodegradable

Not all biodegradable plastics are made from renewable resources. Materials 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 MORE: Materials shaping the future: Polymerised Lactic Acid (PLA)

What is biodegradation?

Biodegradation is the process by which microorganisms break down materials into naturally occurring substances such as carbon dioxide, water and biomass. For biodegradation to occur, the material must be capable of being metabolised by microorganisms under suitable environmental conditions.

The rate and extent of biodegradation depend on factors such as temperature, oxygen availability, moisture, microbial activity and time. These conditions vary significantly between environments, which is why a material that biodegrades in an industrial composting facility may not biodegrade in a home compost system or the natural environment.

Compostable materials are specifically designed to biodegrade under defined conditions and timeframes set out in recognised compostability standards, such as AS 4736, AS 5810 and EN 13432.

What are oxo-degradable plastics? 

Historically, some oxo-degradable plastics were marketed using environmental claims that contributed to confusion between fragmentation, biodegradation and compostability. Oxo-degradable plastics, also referred to as oxo-fragmentable plastics, are conventional plastics that contain additives designed to accelerate fragmentation when exposed to heat, light or oxygen. Unlike biodegradable plastics, these materials do not undergo complete biodegradation through the action of microorganisms.

Biodegradability is an inherent property of a material. When biodegradable materials break down under suitable environmental conditions, microorganisms convert them into naturally occurring substances such as carbon dioxide, water and biomass. Certified compostable plastics are designed to achieve this process within the conditions and timeframes specified by recognised compostability standards.

By contrast, oxo-degradable plastics fragment into progressively smaller pieces, creating microplastics that can persist in the environment. They do not meet recognised compostability standards such as EN 13432, AS 4736, AS 5810 or ASTM D6400, and are therefore not considered compostable.

Because these materials can resemble biodegradable or compostable plastics, they have contributed to confusion around environmental claims and can contaminate organics recovery systems if disposed of incorrectly. This distinction highlights the importance of recognised certification when selecting compostable products.

READ MORE: European Bioplastics statement on oxo-degradable plastics

What is the difference between oxo-fragmentable and biodegradable plastics?

Although they are sometimes confused, oxo-fragmentable and biodegradable plastics behave very differently at the end of their life.

Oxo-fragmentable plastics are conventional plastics containing additives that accelerate fragmentation when exposed to heat, light or oxygen. Rather than being broken down by microorganisms, these materials fragment into increasingly smaller plastic particles, creating microplastics that may persist in the environment.

Biodegradable plastics, by contrast, are designed to be broken down by naturally occurring microorganisms into carbon dioxide, water and biomass under appropriate environmental conditions. Where these materials meet recognised compostability standards such as EN 13432, AS 4736, AS 5810 or ASTM D6400, they may also be certified compostable.

Because oxo-fragmentable plastics do not meet recognised compostability standards, they are not suitable for commercial composting systems. Their similarity to compostable products has also contributed to confusion around environmental claims and contamination of organics collections.

Biodegradability is a pre-requisite to compostability

To be recovered for organic recycling (composting) a material or product needs to be biodegradable. 

Biodegradability refers to a material’s ability to be broken down by microorganisms (like bacteria and fungi) into water, carbon dioxide, and biomass. Crucially, biodegradability is determined by chemical structure—not by the source of the raw material. This means fossil-based raw materials (like PBAT) can be biodegradable, while some renewable, bio-based materials are completely non-biodegradable.

Compostability is a specific type of biodegradability. For a product to be considered compostable, it must break down under precise environmental conditions (specific temperature, moisture, and timeframes) without leaving toxic residues or microplastics behind.

To ensure packaging breaks down properly, materials are certified against internationally recognised compostability standards:

• Commercial / Industrial Composting: Standards such as AS 4736-2006 (Australia), EN 13432 (Europe), and ASTM D6400 (USA) require high-temperature facilities to break materials down.

• Home Composting: Standards like Australia's AS 5810-2010 certify that a product can break down naturally in lower-temperature home garden compost bins.

Certification bodies and global standards

Internationally recognised bodies such as TÜV Austria and DIN CERTCO issue third-party certifications for compostability—such as the OK compost HOME and OK compost INDUSTRIAL marks.

While Australia’s commercial composting standard (AS 4736-2006) was based on Europe’s EN 13432, the Australian standard includes additional stringent requirements, such as earthworm ecotoxicity testing. Because of this, European certificates alone may not satisfy Australian regulatory standards.

The Seedling Logo & Home Compostable Mark in Australia

To help businesses and consumers identify legitimate compostable packaging, the Australasian Bioplastics Association (ABA) administers two key verification schemes in Australia and New Zealand:

• The Seedling Logo: Licensed from European Bioplastics, this green seedling mark proves a product meets AS 4736 for commercial composting facilities.

• The Home Compostable Verification Logo: Featuring a home compost bin icon, this mark verifies compliance with AS 5810 for backyard composting.

Any product carrying these logos must display a valid ABA certification license number to verify its claims.

READ MORE: 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 in this category include many different plastic materials. They do not have specified characteristics and characterisation does not indicate that a product is compostable.

Resin Identification Codes were developed to identify polymer types rather than verify environmental performance or end-of-life pathways. As a result, the #7 symbol alone should not be used to determine whether a product is suitable for composting.

Instead, businesses and consumers should look for recognised compostability certification marks, such as the Seedling logo, OK compost INDUSTRIAL, OK compost HOME, BPI Certified Compostable, or certification marks issued by the Australasian Bioplastics Association (ABA). These marks indicate that a product has been independently assessed against recognised compostability standards.

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 

Understanding where a product is intended to biodegrade is just as important as understanding whether it biodegrades.

Terms such as biodegradable and compostable are often used interchangeably, despite referring to different end-of-life pathways. A product may biodegrade in a commercial composting facility, a home compost system, soil, or another specific environment, but this does not mean it will biodegrade under all conditions.

When evaluating packaging, businesses should consider the intended disposal environment and look for evidence that any environmental claims have been independently verified. Claims such as compostable, home compostable or marine biodegradable should always be supported by recognised certification or testing against the relevant standard.

Accurately communicating end-of-life helps businesses make informed procurement decisions, reduces contamination of waste streams and ensures products are directed to the most appropriate recovery pathway.

READ MORE: 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 continue to represent a relatively small proportion of global plastics production, but they play an important role in applications where packaging is likely to become contaminated with food and can be recovered alongside organic waste.

Their future growth will depend not only on material innovation, but also on the continued development of composting infrastructure, clear regulatory frameworks, recognised certification and consistent collection systems. Without appropriate end-of-life pathways, the environmental benefits of compostable packaging cannot be fully realised.

As the market continues to evolve, it is important to distinguish between bio-based, biodegradable and certified compostable materials. Understanding these differences helps businesses select packaging that aligns with its intended recovery pathway while avoiding misleading environmental claims.

Choosing the right packaging

Understanding the differences between bio-based, biodegradable and certified compostable materials is the first step towards making informed packaging decisions. Selecting the right material depends on how the product will be used, collected and recovered at the end of its life.

We work with businesses to navigate material selection, certification requirements and end-of-life considerations, helping ensure packaging aligns with both operational needs and recognised compostability standards.

Whether you're reviewing your current packaging or exploring certified compostable alternatives, our team can help you identify products that are appropriate for your application.

Get in touch to discuss your packaging requirements and explore our range of certified compostable solutions. Email us at hello@ecoware.co.nz.