Oil and gas pipes left on the ocean floor after decommissioning could result in up to 500 tonnes of microplastics being released into the North Sea each year, according to a new study from the University of Plymouth. 

Almost 220,000 tonnes of plastics have been deployed in subsea pipelines and umbilical coatings on the UK Continental Shelf – an area that includes parts of the North Sea, where most oil and gas activity is located, in addition to the North Atlantic, the Irish Sea and the English Channel. 

More than half of this – roughly 120,000 tonnes – remains in the ocean after the natural gas and oil fields are decommissioned as energy companies are allowed unsealed cables to leave in place due to the high-financial cost, technical challenges, and environmental impact of removal.

The new study suggests that these pipes could be an under-explored source of microplastic, as chemical and physical processes in the ocean cause the plastic-lined pipes to degrade over time.

These pipes, researchers’ modelling suggests, could be releasing 4.5 to 500 tonnes of microplastic into the North Sea every year. 

Current estimates suggest that between four and 16.5 tonnes of plastics are estimated to be released into the North Sea from rivers each year.

Microplastics negatively impact marine life, accumulating in their tissues and brains, affecting natural processes by blocking digestion, disrupting hormones and affecting the efficiency of their energy cells.

Based on this new research, the team of researchers have recommended that the environmental consequences of legacy plastics need to be formally integrated into decommissioning decision making. Going forward, these insights should also be considered when planning and consenting to new energy-related installations and other marine infrastructure.

The study’s lead author Dr Freija Mendrik said, “We believe the findings mark an important step forward in understanding the possible environmental risks posed by these plastics and highlight a previously unrecognised potential source of microplastic pollution.”

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