Background

“Microplastics” refers to microscopic plastic debris, commonly accepted to measure a size of 5mm or less in at least one external dimension in size. However, currently there is no precise internationally standardized definition of a microplastic, which can cause confusion in some situations. Sulapac® adopts the definition used by European Chemical Agency, ECHA [1,2], according to which:

“Microplastics means a material consisting of solid polymer containing particles, to which additives or other substances may have been added, and where ≥ 1% w/w of particles have (i) all dimensions 1nm ≤ x ≤ 5mm, or (ii), for fibres, a length of 3nm ≤ x ≤ 15mm and length to diameter ratio of >3. Polymers that occur in nature that have not been chemically modified (other than by hydrolysis) are excluded, as are polymers that are (bio)degradable.”

ECHA’s definition is in line with e.g. the definition of Industrial Biotechnology Innovation Centre, which defines microplastics as

“Very small (<5mm) non-biodegradable plastic particles formed through mechanical degradation of larger pieces of plastics. Biodegradable plastic should not yield microplastics as these will be assimilated by microorganisms. ” [3]

It should be noted, that there is a difference between the definition of compostable plastics and biodegradable plastics. The decomposition of compostable plastics results from biological processes, involving customized mixtures of microorganisms. Compostable plastics degrade in less than 6 months to carbon dioxide (CO2), water, biomass and inorganic compounds without leaving traces of visually distinguishable or toxic residues but require controlled conditions. The decomposition of biodegradable plastics is carried out by microorganisms occurring naturally in nature, such as bacteria, fungi, and algae. Biodegradable materials are fully assimilated, leaving no residues in the natural environment in a specific time frame. [3,4]

The potential environmental and human health risks associated by the presence of microplastic particles in the environment are: (a) small size (typically microscopic) making them readily available for ingestion, and (b) resistance to normal environmental degradation, which will lead in to a long presence and accumulation in the environment after their initial release [5]. It has been observed that it’s possible that accumulating microplastics collect harmful chemicals and pathogens on their large surface area [6, 7]. However, precise understanding of the fate and impacts of microplastics is lacking, but fortunately a lot of research is ongoing in the field.

The two different categories of microplastics are: i) primary microplastics, which are added microplastics (small particles that have originally been fabricated to be micro-size, and added in cosmetics, paints etc.) and  ii) secondary microplastics, which mean microplastics releases (particle emissions) formed due to wearing of macroplastics  [1, 2].

KEY FEATURE: MICROPLASTIC-FREE

Sulapac recipes do not contain any deliberately added micro-size plastic particles (primary microplastics), neither do the Sulapac materials produce microplastic particles due to degradation or wearing (secondary microplastics).

As all other biopolymers, such as collagen and native cellulose, Sulapac disintegrates first into tiny particles. However, in contrast to conventional microplastic releasing plastics, after disintegration Sulapac straw material biodegrades fully into CO2, water and biomass in open environments within a similar time frame as naturally occurring biological materials such as wood and tree leaves in nature. Various tree leaves have shown to disintegrate and biodegrade in nature in 0.5–5 years depending on the tree species and environment [8, 9, 10]. To summarize, as Sulapac material and naturally occurring biological materials fully biodegrade in nature, they do not accumulate, and thus are not capable of collecting harmful chemicals or pathogens that can enrich along the food chain.

Criteria

To some extent, all solid materials release small particles due to wearing.  However, according to ECHA’s definition of microplastics, it is clear that if small (<5mm) particles of the material biodegrade in a defined time frame in open environments, no microplastic emissions are caused.

Several test methods for biodegradation of materials in open environments exist. As sea water is considered to be the most difficult environment for biodegradation, we have chosen ASTM D6691 “Standard Test Method for Determining Aerobic Biodegradation of Plastic Materials in the Marine Environment by a Defined Microbial Consortium or Natural Sea Water Inoculum” as the test method for the biodegradation of small Sulapac particles. In this test the sample is in a powdered (disintegrated / microplastic) form and its molecular level degradation into CO2, H2O and biomass is measured [11].

Validation

In the tests following the ASTM D6691 method, both O2 consumption and CO2 generation were measured for 112 days [Third party study performed by OWS in Oct/2019]. Combined data from the Baltic Sea [Third party study performed by Finnish Environment Institute in Oct/2019] and ASTM tests suggested a full biodegradation of the straw within a timeframe ranging from 2 to 5 years. Also, it should be noted that according to EN 13432 tests, the straw is industrially compostable and that the degradation products are not ecotoxic, an do not exceed the threshold values for heavy metals [4].

With ASTM 6691 test method we have thus proved that the Sulapac Straw particles biodegrade with a similar speed as tree leaves in nature. ECHA has work in progress to define adequate degradation rate (time) of primary (intentionally added) microplastics in the relevant environmental conditions to avoid accumulation of these materials in the environment, but no standardized criteria yet exist [1]. To the best of our knowledge, the comparison of the biodegradation of Sulapac particles to that of naturally occurring biological materials, such as tree leaves or wood, provides scientifically sound criteria to claim that Sulapac is truly a microplastic-free material.

 

References

  1. Annex to the annex xv restriction report Proposal for a restriction- Intentionally added microplastics, European Chemical Agency, ECHA, 2019.
  2. https://echa.europa.eu/fi/-/echa-proposes-to-restrict-intentionally-added-microplastics
  3. Kjeldsen, A. et al., A review of Standards for Biodegradable Plastics, Industrial Biotechnology Innovation Centre (IBioIC), UK, 2019.
  4. CEN EN 13432:2000, Requirements for packaging recoverable through composting and biodegradation – Test scheme and evaluation criteria for the final acceptance of packaging.
  5. Note on substance identification and the potential scope of a restriction on uses of ‘microplastics’, Version 1.1, ECHA, 2018.
  6. Rios, L.M., Jones, P.R., Moore, C. and Narayan, U.V (2010). Quantitation of persistent organic pollutants adsorbed on plastic debris from the Northern Pacific Gyre’s ‘eastern garbage patch’. Journal of Environmental Monitoring 12(12), 2226-2236.
  7. Gallo,, Fossi, C., Weber, R., Santillo, D., Sousa, J., Ingram, I., Nadal, A. and Romano, D. (2018). Marine litter plastics and microplastics and their toxic chemicals components: the need for urgent preventive measures. Environmental sciences Europe 30(1), 13.
  8. Hasanuzzaman and Hossain M. Leaf Litter Decomposition and Nutrient Dynamics Associated with Common Horticultural Cropland Agroforest Tree Species of Bangladesh. International Journal of Forestry Research,Volume 2014; Article ID 805940.
  9. Gustafson F. Decomposition for the leaves of some forest leaves under field conditions. American Society of Plant Biologists, 1943.
  10. Webster, J.R, Benfield, E.F., Vascular plant breakdown in freshwater ecosystems  Rev. Ecol. Syst. 1986. 17:567-94.
  11. ASTM D6691, Standard Test Method for Determining Aerobic Biodegradation of Plastic Materials in the Marine Environment by a Defined Microbial Consortium or Natural Sea Water Inoculum.
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