Greenhouse gas emissions from decommissioning manmade structures in the marine environment: current trends and implications for the future

The decommissioning of manmade structures in the marine environment causes large volumes of greenhouse gas (GHG) emissions to be released. Current GHG emissions calculation methods for decommissioning offshore oil and gas industry infrastructure leave large sources of GHG emissions unaccounted for. The results presented here show that these consequential decommissioning GHG emissions are underreported by 50%. Until now, no study has looked at the cumulative impact of decommissioning, but this study shows that globally offshore oil and gas infrastructure decommissioning has produced 25 MtCO2e to date, around 0.5% of annual global GHG emissions. Importantly, this study also shows that due to the growth of the offshore wind industry, increasing numbers of manmade structures will be emplaced in the marine environment, and GHG emissions from decommissioning will increase 200-fold to 5 GtCO2e by 2067. Crucially, this growth of GHG emissions is not compatible with the Paris Agreement, and new decommissioning methods will be required to meet this challenge.