Biodegradation and non-toxicity of oxo-biodegradable plastics at sea
The objective of the Oxomar project is to assess the fate of oxo-biodegradable plastics (OXO-bio) in the marine environment.
Plastics at sea: a societal, economic and political issue
Among the 300,000 tonnes of plastic waste found today on the surface of the oceans, more than half are made of polyethylene.
The biodegradation of normal polyethylene (PE) by microorganisms is very slow, and a solution proposed by scientists consists of integrating a catalyst that promotes the oxidation of PE to make it more accessible for biodegradation by naturally-occurring micro-organisms.
The lack of knowledge about this product has led to recent measures relating to their marketing in Europe as from July 2021.
The objective of Oxomar is to provide solid scientific data on the performance of OXO-bio at sea.
The project is based on 3 axes which are to evaluate (1) abiotic degradation, (2) biodegradation and (3 ) any toxicity of OXO-bio when released into the sea.
Multidisciplinary methods: from the design of the plastic to the future of OXO-bio’s at sea.
This project is based on the complementarity of the partners who each bring their own skills.
The industrial partner (SYMPHONY) is producing OXO-bio products distributed in more than 60 countries. It supplies the polymers with and without additives to the other partners.
The partner CNEP specialises in the accelerated ageing of polymers using methods combining the effects of ultraviolet light and heat. This is done to reduce time and cost, but does not invalidate the results
The LOMIC partner incubates plastics in aquariums with direct circulation of sea water, assesses their colonization by microorganisms and tests their biodegradability by respirometry, ATP production, heterotrophic activity, ectoenzymatic activity, and environmental genomics.
LOMIC works in close collaboration with the ICCF laboratory which evaluates the rate of degradation and is interested in metabolic pathways by using HPLC, NMR and mass spectrometry tools.
LOMIC also assesses whether there is any toxicity of OXO-bio’s and their additives, in close collaboration with IFREMER based on the development of several biological models: bacteria, phytoplankton, amphioxus, sea urchin, and sea bass.
The complementary disciplines of the partners allows a pooling of results for as complete an assessment as possible of the future of OXO-bio at sea.
It should be noted that there is a fundamental difference between oxo-degradable plastics, which create microplastics which do not biodegrade, and oxo-biodegradable plastics which do not.
Already, several significant advances can be highlighted.
“First of all, we were able to identify the microbial communities that colonize OXO-bio at sea.
We showed that they were very different from those that are conventionally found in the surrounding seawater.
The populations found on the most oxidized OXO-bio are also very different than on the non-oxidized OXO-bio’s or on the control PE.
The bacterial activity is also higher there, which implies biodegradation in natural environment.
This hypothesis is reinforced by observing the same tendencies when plastics are then placed in a medium without any other carbon source.
We were able to detect toxicity of certain formulations of OXO-bio whose pro-oxidant additives contain Cobalt.
On the other hand, no toxicity is detected for the additives based on manganese and / or iron, which make it possible to achieve similar levels of oxidation after aging.
This result will have direct repercussions on the choice of additives used by manufacturers in the design of OXO-bio plastics.
In the second part of the project, the use of isotopic tracers will allow direct demonstration of biodegradability.
This technological breakthrough will also make it possible to determine the rates of biodegradation of OXO-bio by bacteria, as well as to identify which marine bacteria are capable of taking part in the complex biodegradation processes.
These results could have significant consequences on the OXO-bio market, but also more generally on the biodegradable plastics market.
Scientific productions and patents
Submission of a SOLEAU N ° DSO2017012612 (20/12/2017) envelope for the protection of the protocol “Determination of the aerobic biodegradability of plastics in seawater”
Marine plastic litter is a global environmental problem (descriptor 10 of the EU Marine Strategy Framework Directive) since almost 10% of the 299 million tons of plastic produced worldwide gets accidentally or deliberately into the environment.
The oceans are considered as the ultimate recipient of plastic litter.
Plastics containing pro-oxidant additives called oxo-biodegradable (OXO-bio) have been on the market worldwide for at least 15 years.(10% of the plastic bags in France are OXO-bio) as material promising biodegradability, but their performance in marine waters has not until now been thoroughly investigated.
The OXOMAR project gathers together the largest manufacturer of OXO-bio in Europe (Symphony Environmental Technologies Plc), together with a company specialized in valorization of academic researches on polymer aging (CNEP), and three French academic units (ICCF, LOMIC, IFREMER) specialized in chemistry of materials, marine microbiology and ecotoxicology.
This project presents several novelties including:
- the use of artificial aging to evaluate the fate of OXO-bio of different compositions (including an OXO-HYDRO hybrid polymer) in the Oceans related to abiotic environmental factors,
- the combination of innovative methodologies using stable isotope-labelled 13C-OXO-bio plastic to deliver the first estimation of the OXO-biodegradation rate at sea, together with the original identification of the bacteria performing this biodegradation,
- the evaluation of the possible toxicity of OXO-bio by studying both the ingestion of micro-plastics and the leaching of pro-oxidant additives, by using an unprecedented set of marine organisms from various trophic levels, habitats and feeding behaviors.
The evaluation of the fate of new formulations of plastics in the environment is a societal and environmental concern, which perfectly fits with the objective of the “Défi 1” (ORIENTATION 4).
The potential for scientific breakthrough is very high in this project, since very few studies have been done so far on the performance of OXO-bio in marine waters.
The new research results obtained in this PRCE project will be mutually beneficial for the academic and industrial sectors and for the market of OXO-bio in general.
For instance, “the impact of the use of oxo-biodegradable plastic carrier bags on the environment” has been identified as one of the priorities of the European Council and Parliament for the reduction in consumption of plastic bags (Art. 20a (2) of Directive 2015-720).