Marine pollution /
Marine pollution / Marine degradation Plastics, biodegradation, and risk assessment Bioplastics: facts and perceptions After 25 years on the market, we ought to know a lot about bioplastics. Standardisation has exacted definitions for the term, testing methods have validated their proper recovery and, above all, industry has established a clear purpose for their intended use. However, despite these foundations, knowledge of what bioplastics actually are remains confined to small circles of experts while public opinion is at best confused. Under these circumstances, the spread of myths and misinformation can produce a ripple effect that threatens the acceptance of bioplastics as a whole. Some concepts are often misunderstood (e. g. bio-based is often synonymized with biodegradability (in this article we will use the term bioplastics to mean biodegradable plastics); the existence of standards is not properly valued, so much so that sometimes we see “biodegradable” plastics in quotation marks implying that the supposed biodegradability has yet to be demonstrated. Bioplastics and the marine environment The lack of clarity about bioplastics recently surfaced in discussions of marine litter. The problem of plastic marine debris is not new; careless waste management requires a serious investment in awareness, prevention, and recovery programs at global scales. However, bioplastics have been unwittingly dragged into the debate, with the misperception that they could easily solve the chronic problem of marine litter. The bioplastics industry does not consider biodegradability as a license for littering in the environment for several reasons that follow. The value of biodegradability Packaging and consumer products must have the potential to be recovered in some way at their end of use. In certain contexts, biodegradability allows recovery through organic recycling. This option is contemplated by the European Directive on Packaging [1] and it is beneficial whenever packaging is mixed with kitchen waste (biowaste). In fact the combination of plastic/ biowaste is not recyclable: food dirties the plastic and plastics contaminate food. However the combination of bioplastic/biowaste is recyclable into compost. The CEN standard EN 13432 [2] identifies packaging for organic recycling but makes no claims of biodegradability in any other environment including the sea. The EN 13432 scope is crystal-clear; there is no room for misunderstanding. Biodegradable plastics and recycling The contamination of plastic recycling represents another issue that surfaces whenever a debate on bioplastics starts. What’s surprising is that technically speaking plastics recycling simply does not exist because the term plastics is a collective term including different materials that are incompatible with one another and can only be recycled separately. Cross contamination is always an impediment to recycling (e. g. non-biodegradable plastics interfere with recycling of biowaste). The management of end-of-life must comply with the specific features of each product and waste stream. Whenever separate collection is practiced, bioplastics are recoverable through organic recycling and incentivize proper waste management. Biodegradation in nature To avoid misleading communications, it is critical that the term biodegradable only be associated with the relevant degradation environment (where) and its associated conditions (how much and how long). In agriculture, tests specific to soil define mulch film Fig. 1:Testing degradation in an aquarium (photo: HYDRA Institute for Marine Sciences) Fig. 2: Testing biodegradation in sediment 16 bioplastics MAGAZINE [02/16] Vol. 11
Marine pollution / Marine degradation By: Francesco Degli Innocenti Ecology of Products and Environmental Communication Novamont, Novara, Italy biodegradation because this depositional environment is microbiologically different from composting. Similarly, tests specific to the marine environment are now under development (cf fig. 1). Novamont studied the behaviour of MATER-BI through ASTM [3] and ISO [4] test methods (cf fig. 2). Tests performed in marine sediments showed biodegradation (as CO 2 evolution) in excess of 90 % (absolute or relative to cellulose) in less than one year; Certiquality (Certification Institute; Milan,) verified these results within the European Commission’s pilot program ETV [5]. These results are in agreement with previous findings [6]. Biodegradability and risk assessment How should we interpret these very promising biodegradation data? Generally speaking, the environmental risk depends on the concentration of the environmental stressor and on its residence time in the environment. The lower the concentration and the shorter the residence time, the better. Bioplastics do not immediately disappear upon exposure to the sea. However, biodegradability is a factor that reduces the risk by reducing the stressor’s residence time. Therefore, on one hand the idea of solving the problem of plastics in the ocean just by shifting to bioplastics is unfounded. On the other hand, for those applications where accidental release is certain or very probable, biodegradability can become a means of decreasing the environmental risk. Materials that show full and relatively fast biodegradation may be suitable for plastic products known to wear down or become stranded (for example, fishing gear) and scatter into the sea. Bioplastics like MATER-BI materials hold promise for aquaculture professional applications (e. g. nets for mussels farming, cf. fig. 3) where the disposal of plastic waste is an inevitable outcome. Fig. 3: Mussel farming nets (Source unknown, found e. g. in presentations by ISPRA [7]) www.novamont.com [1] European Parliament and Council Directive 94/62/EC of 20 December 1994 on packaging and packaging waste [2] EN 13432:2000 Packaging. Requirements for packaging recoverable through composting and biodegradation. Test scheme and evaluation criteria for the final acceptance of packaging [3] ASTM D7991 – 15 Standard Test Method for Determining Aerobic Biodegradation of Plastics Buried in Sandy Marine Sediment under Controlled Laboratory Conditions [4] ISO/DIS 19679 Plastics — Determination of aerobic biodegradation of non-floating plastic materials in a seawater/sediment interface — Method by analysis of evolved carbon dioxide [5] http://iet.jrc.ec.europa.eu/etv/aerobic-biodegradation-mater-biaf03a0-and-mater-bi-af05s0-mater-bi-third-generation-undermarine [6] F. Degli Innocenti (2012) Single-use carrier bags: littering, bans and biodegradation in sea water. Bioplastic Magazine 042012 (vol 7):44- 45 [7] http://oceania.research.um.edu.mt/cms/calypsoweb/images/ meeting2/catania-meeting/Andaloro.pdf bioplastics MAGAZINE [02/16] Vol. 11 17
