Thousands of oil and gas structures have been installed in the world’s oceans over the past 70 years to meet the population’s reliance on hydrocarbons. Over the last decade, there has been increased concern over how to handle decommissioning of this infrastructure when it reaches the end of its operational life. Complete or partial removal may or may not present the best option when considering potential impacts on the environment, society, technical feasibility, economy, and future asset liability. Re-purposing of offshore structures may also be a valid legal option under international maritime law where robust evidence exists to support this option. Given the complex nature of decommissioning offshore infrastructure, a global horizon scan was undertaken, eliciting input from an interdisciplinary cohort of 35 global experts to develop the top ten priority research needs to further inform decommissioning decisions and advance our understanding of their potential impacts. The highest research priorities included: (1) an assessment of impacts of contaminants and their acceptable environmental limits to reduce potential for ecological harm; (2) defining risk and acceptability thresholds in policy/governance; (3) characterising liability issues of ongoing costs and responsibility; and (4) quantification of impacts to ecosystem services. The remaining top ten priorities included: (5) quantifying ecological connectivity; (6) assessing marine life productivity; (7) determining feasibility of infrastructure re-use; (8) identification of stakeholder views and values; (9) quantification of greenhouse gas emissions; and (10) developing a transdisciplinary decommissioning decision-making process. Addressing these priorities will help inform policy development and governance frameworks to provide industry and stakeholders with a clearer path forward for offshore decommissioning. The principles and framework developed in this paper are equally applicable for informing responsible decommissioning of offshore renewable energy infrastructure, in particular wind turbines, a field that is accelerating rapidly.

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