Image: The main Standards for testing oxo-bio plastic are ASTM D6954 (USA); BS8472 (UK); AFNOR AC T51-808 (France); and SPCR 141 (Sweden)

STANDARDS

The main Standards for testing oxo-bio plastic are ASTM D6954 (USA); BS8472 (UK); AFNOR AC T51-808 (France); and SPCR 141 (Sweden).  Variants of these standards have also been adopted in other countries, such as SASO 2879 in Saudi Arabia.

ASTM D6954 contains six pass/fail criteria.  1. For the abiotic phase of the test (6.3 – 5% e-o-b and 5,000DA) 2. The tests for metal content and other elements (6.9.6), 3. Gel content (6.6.1), 4. Ecotoxicity  (6.9.6 -6.9.10), 5. PH value (6.9.6) and 6. For the biodegradation phase (for unless at least 60% of the organic carbon is converted to carbon dioxide the test cannot be considered completed).

It is for customers and governments to decide what timescales are acceptable to them.

European standard EN 13432 and ASTM D6400 apply to biodegradation of plastic packaging under industrial composting conditions, but they not appropriate for testing oxo-biodegradable plastics. This is because they are based on measuring the emission of carbon dioxide during degradation. Hydro-biodegradable plastic is compliant with EN 13432, precisely because it emits CO2 (a greenhouse gas) at a very high rate.  If a leaf were subjected to the CO2 emission tests included in these Standards it would not be considered biodegradable or compostable!

EN 13432 does not apply at all to applications other than composting of packaging. Para. 1 of EN13432 itself makes it clear that it does not apply to packaging waste which may end up in the environment through uncontrolled means, ie as litter.

NON-TOXICITY

The Oxo-biodegradable industry is as much concerned as anyone that its products should not introduce toxicity into the environment, and for this reason the standards for oxo-bio require testing to confirm that the residues are harmless. Essentially oxo-bio plastics are made from the same materials as conventional plastics, with the addition of only 1% of a masterbatch (most of which is itself ordinary polymer), and they have to pass the same tests in EN 13432 as “compostable” plastic to ensure that there is no toxicity and no metals exceeding the prescribed limits.

THE MARINE ENVIRONMENT

According to Dr. Jean-François Ghiglione  “Oxo-bio plastic will float and be at almost all times subjected to UV light, which accelerates the abiotic phase of degradation. This is not always the case on land, where plastic pieces are often covered by soil, leaves etc. and are less exposed to UV light.”  He points out that “there are specific bacteria living in the “sea-surface microlayer” (the top millimetre of the ocean surface), where bacteria are different from those further below the surface. The bacteria in the sea-surface microlayer are particularly adapted to a hydrophobic   environment (e.g. where oil materials are floating) and these bacteria are known to present a high capability for hydrocarbon degradation.”

“Some marine bacteria, such as Alcanivorax borkumensis and R. rhodochorous are noted for their ability to biodegrade hydrocarbons and they are ubiquitous in the oceans.  They occur in low concentrations in unpolluted seas but are observed to accumulate in waters polluted by oil spills. When presented with a source of carbon which is recognisable to the microorganisms as food, it seems therefore that they will respond with increased populations. The relatively low concentrations of microorganisms found in unpolluted oceans is not therefore a reason for expecting slow biodegradation.”

Evidence is available – from tests done in real time at Bandol on the coast of France that oxo-bio plastic will degrade to low molecular-weight materials under natural conditions in water, and samples aged under those conditions were studied at Queen Mary University London where the abiotically degraded plastic was presented as the only source of carbon available to the bacteria. The samples were proved to be biodegraded by bacteria commonly found in the oceans, and separate samples were biodegraded by bacteria commonly found on land.  The degraded plastic was also proved to be non-toxic to those bacteria.

PROPENSITY TO LITTER?

It is sometimes claimed that biodegradable plastics are likely to encourage littering, but this is rarely advanced as an objection to bio-based plastics.

Even if there were a label describing a product as oxo-biodegradable, it is unlikely that the people who cause litter will look for the label before deciding to throw a plastic item out of a car window. Further, even if it were true that biodegradability encourages littering, and supposing that there would be 10% more litter – is it preferable to have 110 plastic items in the environment which will degrade and biodegrade in a few years or even months, or 100 plastic items which will lie or float around for many decades?

It is not acceptable to continue debating this speculative proposition any longer, while thousands of tonnes of conventional plastic are getting into the environment every day, which will accumulate and pollute the environment for decades into the future.

A Life-cycle Assessment by Intertek shows that when the litter metric is included OBP is the best material for making carrier bags. 

THE EUROPEAN UNION

The January 2018 report of the EU Commission was concerned about microplastics, and recommended that the European Chemicals Agency (ECHA) be requested to make a study.  This request was made under Art 69 of the REACH Regulation 2006/1907, and the OPA submitted a substantial body of evidence to ECHA.  See https://www.biodeg.org/opa-comments-on-european-union-legislation/

Ten months into the study, ECHA informed us that they were not yet convinced that microplastics are formed, and requested more time.  The Commission then terminated the study, so there is no scientific justification for any ban from the European Union’s own scientific experts, and the purported ban is probably unconstitutional.  ECHA also received a large number of submissions from all over the world that a ban of this technology would be seriously damaging for the environment if it were followed in their countries.

Biodeg