The Case for Marine Biodegradable Plastics

Evidence and standards for plastics that must biodegrade in high-leakage marine sectors

The 2019 EU Single-Use Plastics Directive (SUPD) rightly made plastic pollution a legislative priority. Yet for certain sectors like fisheries, aquaculture, and coastal protection, the tools the Directive relies on are not enough. These are high-leakage environments where prevention, reuse, and recycling cannot fully solve the problem. When gear is lost at sea, it stays there. The question is no longer whether we need alternatives, but whether those alternatives can genuinely disappear.

The science says they can. Over the past decade, a growing body of field and laboratory evidence has confirmed that certain bio-based materials, most notably polyhydroxyalkanoates (PHAs), biodegrade completely and harmlessly across a wide range of marine environments, from warm coastal waters to cold deep-sea sediments exceeding 5,000 metres depth. PHA leads the evidence base, but other materials including cellulose-based polymers are also showing promising results, pointing toward a broader family of genuinely marine-biodegradable solutions. Real-world applications in fishing gear, aquaculture ropes, mussel nets, and oyster farming have begun to show that these materials can match the functional performance of conventional plastics while leaving no persistent residue behind.

This report, produced by GO!PHA, brings together the scientific evidence on how marine biodegradation works, what conditions shape it, and where it matters most. It looks at the current state of standardisation, explains why harmonised EU standards have so far been missing, and makes the case for why the 2027 SUPD evaluation is the right moment to establish them.

The priority remains keeping plastics out of the ocean altogether. But for product categories where loss is genuinely unavoidable, having a material that safely completes its life cycle in the marine environment is far better than one that persists for centuries. For these cases, including SUPD-covered items like food containers, cups, cutlery, and wet wipes that regularly reach waterways and coastal environments despite best efforts, marine biodegradability is not an excuse for poor waste management. It is a responsible safety net. Recognising it as such in policy, in standards, and in sector-specific regulation would reduce long-term ecological damage without waiting for recovery infrastructure that, in marine settings, may never be sufficient.