Inconsistent definitions of plastic across UK regulations are creating uncertainty for bio-based and biodegradable material manufacturers, according to a report published today by BB-REG-NET, a regulatory network for bio-based materials.

The report, Plastic definitions in UK regulation: How plastic is defined in regulations and implications for bio-based and biodegradable alternatives, identifies discrepancies between how major UK regulations define plastic, with materials treated differently under various regulatory frameworks despite having identical properties.

The analysis shows that whilst both the Single-Use Plastics Ban and Plastic Packaging Tax base their definitions on the REACH polymer definition, they apply different exclusions that create regulatory inconsistencies. The Single-Use Plastics Ban excludes all natural polymers that have not been chemically modified, whilst the Plastic Packaging Tax only exempts cellulose-based polymers that have not been chemically modified.

"Although regulatory plastic definitions are based on scientific principles and definitions they are not always consistent, being tailored to meet the precise needs of the regulation at the time it is written," said Polly-Ann Hanson, Bioeconomy Consultant for Alder Bioinsights and lead author of the report. "This divergence in definitions can lead to market confusion and potentially frustration, particularly in what 'plastic-free' labels mean and how plastics are marketed, regulated and taxed."

Treatment of natural polymers varies

The report highlights three key materials that demonstrate these inconsistencies: cellulose is exempt from both regulations, starch is exempt from the Single-Use Plastics Ban but subject to the Plastic Packaging Tax, and polyhydroxyalkanoates are subject to both regulations despite being produced by natural biological processes.

A key finding is that neither regulation clearly defines what constitutes chemical modification or natural polymers, creating interpretative challenges for manufacturers developing novel bio-based materials. The report notes that ECHA guidance suggests industrially fermented polymers are not considered natural even when structurally identical to naturally occurring versions.

The research identifies the consequences of the different definitions of plastic on innovation in new materials. Novel polymers derived from plant proteins, seaweed, alginates and chitin may face classification uncertainties under current definitions, potentially creating regulatory grey areas that could discourage investment in sustainable alternatives.

The report also addresses consumer perception challenges, noting that negative public attitudes towards plastics are driving some companies to pursue plastic-free certification even for materials that may technically qualify as plastic under regulatory definitions.

Policy recommendations

Key recommendations include harmonising definitions across regulations to ensure consistent treatment of materials with similar properties, clarifying terminology around natural polymers and chemical modification to reduce interpretative uncertainty, developing protocols for assessing novel materials to accommodate emerging technologies, and aligning policy objectives with environmental outcomes rather than material origins alone.

The study demonstrates how some companies have addressed current regulations through approaches using natural plant polymers, including Xampla's plant protein materials and Notpla's seaweed-based packaging.

The report also highlights work from the National Physical Laboratory, the UK's national measurement institute. NPL has announced an approach for evaluating whether a material is plastic-free as defined by regulation.

"Standards and definitions are vital for the operation of any industry," said Alexandra French, Chief Executive of Xampla. "At Xampla, we have experienced the benefits of innovating materials that are 'natural polymers' as defined by EU REACH regulations and are recognised under the SUPD and by NPL as 'plastic-free'. By standardising definitions across regulations aimed at addressing plastic pollution, the packaging industry can take another step towards a plastic-free future."

However, the report states that as more novel materials enter the market, existing definitions may become increasingly inadequate for classification purposes, potentially creating barriers to commercialisation of sustainable innovations.

The research forms part of BB-REG-NET's initiative to provide evidence-based guidance for bioeconomy policy development and support the transition to sustainable materials.