Bioplastic Glossary

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The Rise of Plastic Alternatives

Fossil-fuel based single-use plastic does not biodegrade in a reasonable amount of time, and is the main source of plastic pollution affecting our ocean. In recent years, new materials collectively called “bioplastics” have entered the market. These products are advertised as a sustainable alternative to plastic, and often labeled as biodegradable or compostable.

There is a lot of confusion and mixed results as to whether these products actually break down in the natural environment, and therefore, if they should be considered a sustainable alternative to plastic. [www.surfrider.org The Surfrider Foundation] advocates for source reduction of single-use plastics, and encourages the adoption of reusable items as the best way to move away from single-use plastic. Furthermore, Surfrider does not advocate for the use of “bioplastic” materials as the preferred alternative to conventional plastics. This is because most bioplastic materials do not break down in the marine environment, shift the burden to other resources, and perpetuate the single-use mentality. Surfrider has compiled this comprehensive document to help consumers, businesses, and the general public make informed choices as they try to live an ocean friendly lifestyle.

The Problem with Bioplastics

Bio-based materials can be cataloged into fast, medium and slow degraders, based on how much mass they lose after 90 days of home composting. According to the European Commission of Science for Environmental Policy, the fast degraders are predominately made from high levels of starch, the medium degraders are based on wood or coconut fibers, and the slow degraders tend to be composed of polylactic acid (PLA).[1]

While PLA products and other bioplastics are commonly touted as a sustainable alternative to conventional plastics, these products are only biodegradable in industrial composting plants with high humidity and temperatures, and there only about 200 of these facilities nationwide. Thus, PLA plastic will not break down into natural elements (“biodegrade”) in your backyard composting pile, the landfill, or most importantly, the ocean. In addition, if added to the recycling bin, PLA plastics can contaminate recycling processes because they are chemically different from traditional plastics.[2] The glossary below gives definitions and standards for the common words used to describe single-use disposable items.

Glossary of Bioplastic Terms

There is a lot of confusion about the definitions of terms like bioplastics, biodegradability, and compostability. It turns out these definitions can be more complicated than they seem - so we did some digging, hit the literature, and identified the following definitions as the most generally accepted. Findings indicate that the best method of pollution prevention continues to be avoiding single-use packaging all together.

Degradable

Degradable means that a material’s polymers are able to be partially or completely physically altered from environmental factors including light (photodegradation), heat (thermal degradation), chemical (including oxidation), moisture, and/or biological; causing the material to lose properties.[3] [4] This term has no associated timeline, level of breakdown, or avoidance of toxic residues. Therefore, products labeled as just degradable do not provide an effective level of plastic pollution prevention.

Biodegradable

The term “biodegradable” is used to describe plastics and materials able to degrade and break down into their individual molecules and biomass through the use of living organisms (mainly microorganisms like bacteria, fungi, algae or their enzymes).[5] [6] [7] Some definitions include the term “partial” breakdown,[8] as opposed to complete breakdown into molecules and biomass, so there is also the term “complete biodegradation”. Essentially, the term biodegradable is meaningless unless it is accompanied by a specified timeframe and assurance that no toxic residue will remain.

Compostable

A great definition for compostable is: “materials which biodegrade in a composting process through the action of naturally occurring microorganisms and do so to a high extent within a specified timeframe. The associated biological processes during composting will yield C02, water, inorganic compounds and biomass which leaves no visible contaminants or toxic residue/substances.”[9] This term is regulated by multiple standards, including EN Standard 13432, ASTM D6400, & ASTM 6868. Often times, products labeled as compostable can only meet these criteria in an industrial composting facility. Therefore, products labeled as compostable can only provide effective plastic pollution prevention if disposed of at an industrial composting facility.

Home Compostable

Ideally home compostable would mean that materials are able to meet the “compostable” specifications without the need for an industrial composting facility. For instance, the material can (1) biodegrade to a high extent within 180 days (2) fully disintegrate in a way that makes the materials indistinguishable from the compost soil and (3) not have any ecotoxicity; through backyard compost methods such as worm bins or compost piles. Currently, there is no specific standard regulating this term,[10] so while there is promise for the benefit of home compostable plastics, without assurance that products will meet the necessary criteria, the term "home compostable" may not provide an effective level of plastic pollution prevention. That said, home composting for natural food waste like fruits and vegetables, plant debris, and even paper products with minimal ink or chemical processing has some fantastic benefits.

Marine Degradable

Marine Degradable generally means a material has the ability to completely biodegrade under marine environmental conditions including aerobic marine waters or anaerobic marine sediments within a specified timeframe, leaving no toxic substances or residue (doesn’t have any ecotoxicity). Some will only apply this term to non-plastics, such as cellulose materials like paper. A standard providing more clarity, assurance, and testing requirements needs to be provided for this term to be effective and meaningful.

Oxo-biodegradable

Oxo-biodegradable means that the plastic (generally a conventional fossil-fuel based polymer) has an additive that speeds up the degradation process (a pro-oxidant), causing the plastic to break down into smaller particles, especially when exposed to heat or light. There is no explicit time-frame associated with this term, and no assurance that the smaller particles will completely biodegrade in a timely manner. In the meantime, these small plastics become more bioavailable to wildlife. Oxo-biodegradable products cannot be composted, and they negatively impact the recycling stream by reducing the structural integrity of the final product.[11] Therefore, products labeled as oxo-biodegradable do not provide an effective level of plastic pollution prevention.

Synthetic Polymers

Synthetic polymers simply mean “made by chemical synthesis” or “man-made”, and can be derived from petroleum/fossil fuels or bio-based materials (like corn), and once processed, can have the same properties, including lack of ability to degrade, regardless of raw material. Synthetic plastics frequently contain toxic additives to make them have preferred qualities like being malleable, water resistant, heat resistant, and more.[12] There are no assurances that synthetic polymers can completely biodegrade within a specific timeline, meet compostable standards, or be "marine degradable".

Bioplastics

The term “bioplastics” is used to describe both fossil fuel-derived plastics that are biodegradable, and biomass or renewable resource-derived plastics (termed bio-based plastics).[13] See venn diagram below. Fossil fuel-based plastics that are supposedly biodegradable include PBS (polybutylene succinate) and PCL (polycaprolactone), because they can be “degraded with enzymes and microorganisms”; however, studies do not provide timelines for this to occur, or clarification that treated bioplastics (those containing common additives) are able to completely biodegrade within a specified timeline.[14] Since bioplastics can include fossil-fuel based plastics, products labeled simply as bioplastic do not provide an effective level of plastic pollution prevention.

BiodegradabilityofPlasticsSchematic.png


Bio-derived Plastics

Bio-derived (or bio-based) plastics are plastics derived from biomass or renewable sources, instead of fossil fuels. It’s preferred that bio-based products are made from waste materials, as opposed to raw materials, to prevent additional environmental stressors and land use change. One of the most popular bio-based plastics is polylactide (PLA), which is generally certified compostable;[15] however, not all bio-based plastics are completely biodegradable or compostable, including bio-polyethylene (PE) and bio-polyamide (Nylon 11), which act similarly to petroleum-derived plastics.[16] There are some emerging bio-derived plastics, including polyhydroxyalkanoates (PHA), which show promising characteristics of being compostable and completely biodegradable even landfills, but this technology is still in development, and certifications will clarify which standards this product meets.

Biopolymers

Biopolymers are materials made by living creatures, and include chitin, lignin, cellulose, protein fiber and plant polyester, to name a few. Much of the emerging materials for plastic substitutes are made from biopolymers. Because these materials are made directly from living creatures, they are expected to be compostable, completely biodegradable, and ideally marine degradable within a reasonable timeframe, but additional research and policy guidance need to be conducted to provide assurance. Just like with bio-derived plastics, biopolymers can be processed in manner that makes them have the same long-lasting characteristics as petroleum-based plastics.

Petroleum-based Plastics

Petroleum-based plastics are essentially conventional plastics: cheap, plentiful, and highly resistant to biodegradation, regardless of environmental conditions. This resistance is actually a sought after quality during the product’s use phase, but dangerous for end of life. These materials have not been shown to biodegrade in our lifetime, even with controlled experiments using a wide range of microorganism strains.[17] Additionally, these plastics extend our reliance on harmful fossil fuels, as they are made from either naptha (crude oil) or ethane and propane (natural gas). Petroleum-based plastics also release potent greenhouse gas emissions including methane when exposed to sunlight and during degradation.[18]

Summary

UNEPBiodegradablePlastisc&MarineLitterSchematic.png



Conclusion

Suggested Order of Operations for Product Selection

1. Reusable glass or stainless steel
2. Wood or paper without PFAS lining, single-use
3. Try to avoid: Bioplastic, starch or PLA

Substantial efforts are underway by polymer scientists to develop viable bioplastics. However, “None of the [current] alternatives are what they should be,” Daniella Russo, the Plastic Pollution Coalition’s executive director, says. “For an alternative plastic to succeed, it should be non-toxic over its entire life cycle, fully biodegradable in all situations, and cost competitive.” Jacqueline McGlade, chief scientist at the UN Environment Programme, believes that biodegradable plastics are a 'false solution'. “It’s well-intentioned but wrong. A lot of plastics labelled biodegradable, like shopping bags, will only break down in temperatures of 50C and that is not the ocean. They are also not buoyant, so they’re going to sink, so they’re not going to be exposed to UV and break down."

Also keep in mind that although these products may be made from plant rather than petroleum raw materials, the basic chemical structure (PET, LDPE, PVC, etc.) of the plastic bag or bottle is still the same. Equally important to remember is that these bags or bottles are still single use plastics. Reusable bags, bottles or other containers are a much better alternative. Better for the ocean and better for your wallet.

References
  1. European Commission. 2009. Science for environment policy. European Commission DG Environment News Alert Service, edited by SCU, The University of the West of England, Bristol.
  2. Royte, E. 2006. Corn plastic to the rescue. Smithsonian Magazine.
  3. Shah, A.A., Hasan, F., Hameed, A. & Ahmed, S. 2008. Biological degradation of plastics: A comprehensive review. Biotechnology Advances, Vol. 26, No. 3, Pp. 246-265.
  4. UNEP. 2015. Biodegradable plastics & marine litter: Misconceptions, concerns and impacts on marine environments. United Nations Environment Programme (UNEP).
  5. Tokiwa, Y., Calabia, B.P., Ugwu, C.U. & Aiba, S. 2009. Biodegradability of plastics. International Journal of Molecular Science, Vol. 10, No. 9., Pp. 3722-3742.
  6. Shah, A.A., Hasan, F., Hameed, A. & Ahmed, S. 2008. Biological degradation of plastics: A comprehensive review. Biotechnology Advances, Vol. 26, No. 3, Pp. 246-265.
  7. UK Local Authority Guidance. 2011. Concise guide to compostable products and packaging. Association for Organics Recycling.
  8. UNEP. 2015. Biodegradable plastics & marine litter: Misconceptions, concerns and impacts on marine environments. United Nations Environment Programme (UNEP).
  9. UK Local Authority Guidance. 2011. Concise guide to compostable products and packaging. Association for Organics Recycling.
  10. State of California Department of Justice. 2013. Quick reference guide to “biodegradable,” “compostable,” and related claims on plastic products in California. Kamala D. Harris Attorney General.
  11. UK Local Authority Guidance. 2011. Concise guide to compostable products and packaging. Association for Organics Recycling.
  12. UNEP. 2015. Biodegradable plastics & marine litter: Misconceptions, concerns and impacts on marine environments. United Nations Environment Programme (UNEP).
  13. Tokiwa, Y., Calabia, B.P., Ugwu, C.U. & Aiba, S. 2009. Biodegradability of plastics. International Journal of Molecular Science, Vol. 10, No. 9., Pp. 3722-3742.
  14. Tokiwa, Y., Calabia, B.P., Ugwu, C.U. & Aiba, S. 2009. Biodegradability of plastics. International Journal of Molecular Science, Vol. 10, No. 9., Pp. 3722-3742.
  15. UNEP. 2015. Biodegradable plastics & marine litter: Misconceptions, concerns and impacts on marine environments. United Nations Environment Programme (UNEP).
  16. Tokiwa, Y., Calabia, B.P., Ugwu, C.U. & Aiba, S. 2009. Biodegradability of plastics. International Journal of Molecular Science, Vol. 10, No. 9., Pp. 3722-3742.
  17. Tokiwa, Y., Calabia, B.P., Ugwu, C.U. & Aiba, S. 2009. Biodegradability of plastics. International Journal of Molecular Science, Vol. 10, No. 9., Pp. 3722-3742.
  18. Royer S-J, Ferrón S, Wilson ST, Karl DM. 2018. Production of methane and ethylene from plastic in the environment. PLoS ONE, Vol. 13, No. 8.