Abstract
Plastic litter is encountered in aquatic ecosystems across the globe, including polar environments and the deep sea. To mitigate the adverse societal and ecological impacts of this waste, there has been debate on whether ‘biodegradable' materials should be granted exemptions from plastic bag bans and levies. However, great care must be exercised when attempting to define this term, due to the broad and complex range of physical and chemical conditions encountered within natural ecosystems. Here, we review existing international industry standards and regional test methods for evaluating the biodegradability of plastics within aquatic environments (wastewater, unmanaged freshwater and marine habitats). We argue that current standards and test methods are insufficient in their ability to realistically predict the biodegradability of carrier bags in these environments, due to several shortcomings in experimental procedures and a paucity of information in the scientific literature. Moreover, existing biodegradability standards and test methods for aquatic environments do not involve toxicity testing or account for the potentially adverse ecological impacts of carrier bags, plastic additives, polymer degradation products or small (microscopic) plastic particles that can arise via fragmentation. Successfully addressing these knowledge gaps is a key requirement for developing new biodegradability standard(s) for lightweight carrier bags.
Highlights
With a global estimate of over 300 million tonnes of plastic and a trillion plastic bags produced annually, the single-use carrier bag is a curiously iconic ambassador for polymer products [1,2]
The conclusion of this review is that current international standards and regional test methods are insufficient in their ability to realistically predict the biodegradability of carrier bags within wastewater, inland waters and marine environments
This is due to several shortcomings in existing test procedures, the absence of relevant standards for the majority of unmanaged aquatic habitats, as well as a paucity of wider research into the biodegradation of plastic materials within these environments
Summary
With a global estimate of over 300 million tonnes of plastic and a trillion plastic bags produced annually, the single-use carrier bag is a curiously iconic ambassador for polymer products [1,2]. Further to showing high service-life performance in terms of tensile strength and costs per unit weight, carrier bags are often considered an unwanted symbol of plastic pollution This pollution is so ubiquitous that its presence can be used to mark the likely beginning of a new geological epoch called the Anthropocene [3]. — Are there standards that could establish biodegradability product performance and safe environmental credentials for plastic films and bags that might be unintentionally littered?. — What would need to happen to enable the development of a biodegradability standard specification, and a compliance and certification system, for a new generation of plastic bags claiming to be biodegradable in all open environments?. We discuss the current situation concerning biodegradability standards and highlight knowledge gaps that would have a bearing on the development of a plastic biodegradability specification for the open environment. Several other channels of enquiry, through industry and standardization authorities, allowed a fuller understanding of the situation for plastic materials and their biodegradability performance
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