Decommissioning and subsea plastics project (PLASTICS)

What factors influence the breakdown of pipelines and umbilicals, and what risk do these plastics pose to the marine environment?

Plastics from oil and gas infrastructure may pose long-term environmental risks, but with limited understanding of their degradation and ecological impacts, this project aimed to answer pivotal questions surrounding the longevity of plastics in the ocean, their ecological risks, and develop recommendations for consideration in future decision-making processes around decommissioning.

Objectives

• Map the “subsea plastic footprint” to provide the most accurate estimates to date of plastic materials—such as in pipelines, umbilicals and other polymer-based elements—currently found across the UK Continental Shelf (UKCS). By identifying the types and quantities of plastics, researchers hope to map out the full extent of the footprint.
• Refine degradation models and timelines, with the aim of predicting how plastics in subsea infrastructure break down over time, and whether these processes could lead to fragmentation and mineralisation in the local conditions of the UKCS.
• Develop decision-making support criteria to assess risk and make decisions regarding decommissioning of pipelines and umbilicals.

Key Findings

The research has highlighted a significant gap in the understanding of how plastics degrade in subsea environments, especially in relation to depth, pressure, and burial. This uncertainty makes it difficult to accurately assess the ecological risks associated with these materials. While the need to make a decision about the removal of plastics tied to oil and gas infrastructure may not be urgent, it is important that potential issues are given consideration due to the longevity of plastics and the extent of their use in subsea infrastructure.  The insights gleaned from the project’s ongoing analysis will be pivotal in shaping future decommissioning strategies and the findings emphasise the need for policymakers to consider both the environmental costs of plastic removal and the potential risks of leaving the material in place.

Questions in the Pipeline

The project’s goal is clear: to help the oil and gas industry better understand and manage the long-term environmental impact of subsea plastics. However, there are several practical recommendations that could help answer further questions. For example, if plastics were sampled from more diverse subsea locations, it would enable comparisons to be made between sites and build a more complete picture.  Likewise, if innovative techniques like the “cut and lift” method for material retrieval, it might help to preserve critical biofouling and microbial communities which are essential for studying plastic degradation.

As we look ahead, the findings of this project are poised to transform decision-making in decommissioning, ensuring that the economic and ecological costs of plastic removal are carefully balanced. While it is unlikely that plastic pollution from these materials will present an immediate danger, however, the slow accumulation of plastic debris from across our whole society, including that used in pipelines, represents a long-term issue that needs addressing.

In an era where microplastics are recognised as a growing environmental threat, understanding the “subsea plastic footprint” and mitigating their long-term impacts is essential for preserving the health of our ocean.