Decommissioning pipelines used by the oil and gas industry could result in substantial quantities of microplastics being released into the UK’s marine environment annually, a new study has suggested.
Conducted by scientists at the University of Plymouth, the research examined the degradation of plastics in subsea oil and gas pipelines and umbilicals (including hoses and cables) as a previously underexplored source of microplastic pollution.
They estimated that almost 220,000 tonnes of plastics have been deployed in subsea pipeline 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.
They then estimated that more than half of those plastics, 120,000 tonnes, were likely to remain in the ocean after being decommissioned, and that they would be subject to physical and chemical degradation, caused in large by sand abrasion on the seabed.
Using a range of modelling approaches, the study suggests that due to degradation, between 4.5 and 500 tonnes of microplastics could be released into the UK North Sea each year depending on prevailing environmental conditions. For context, between four and 16.5 tonnes of plastics are estimated to be released to the North Sea from UK rivers every year, and 500 tonnes is more than seven times the annual microbead releases from cosmetics into the North Sea prior to them being banned in the UK.
Using a technique called Predicted No-Effect Concentration (PNEC) analysis, the research also indicated that over time the microplastics accumulating from legacy oil and gas plastics have the potential to affect marine life across substantial areas of the environment, adding to the effects of plastic contamination from other sources.
Based on the research, the team recommend that the environmental consequences of legacy plastics need to be formally integrated into decommissioning decision making, and into planning and consenting for new energy-related installations and other marine infrastructure.
The research, which also involved the University of North Carolina, was funded as part of the INSITE North Sea Programme and builds on existing research led by scientists in Plymouth which has examined the sources and effects of microplastics as well as the potential ecological benefits of decommissioned offshore structures.
Dr Sarah Gall
Professor Richard Thompson OBE FRS
