In the oil and gas sector, oil and gas installations, or platforms, have a lifespan and what to do with them on expiry creates a tremendous challenge for the stakeholders, given the ever-present risks associated with oil and gas operations in the context of domestic, regional and international law. Stakeholders include the country that licensed the installation and its operation, the owner/operator of the installation, as well as the neighbouring countries and the citizens of those countries.  Not every oil or gas producing country has an effective legal framework dealing with decommissioning and concomitant environmental imperatives and in such instances, international law may not provide any recourse.

Decommissioning offshore oil and gas platforms presents inherent environmental and socio-economic impacts for which there is no single solution. Older structures that were designed and installed before various laws and regulations were enacted to govern their decommissioning, and some locations being prone to extreme weather conditions, are further complications. The process of decommissioning takes years to complete and that the act itself produces its own environmental hazards.

Decommissioning comprises several components, each subject to environmental considerations in respect of onshore impact, hazardous substances, waste management, energy usage and emissions, as well as marine impact.  The environmental impact can be projected but not with absolute certainty.

A marine environmental impact might include the long-term effects of leaving parts of the structure in place, where abandoned components could result in the release of hydrocarbons up to 500 years or more into the future. In addition, structural components such as the platform legs can last around 300 years and the storage cells can still exist some 1000 years into the future. The structures could cause obstructions to ocean going vessels and fishermen in the area.

It is inevitable, however, that over time the platform legs become a part of the marine environment, providing protected breeding grounds for fish and rock dumps that protect sediment habitats. While the risk of an oil leak  is ever present and demands appropriate monitoring, the vast CO2 emissions generated in deconstructing and repatriating components to shore for recycling should also be considered.  Further, the removal of structures can impact on marine life, due in some cases to sediment disturbance and release of contaminants.  Also, there are components that cannot be recycled which will be dumped in onshore landfills sorely needed for other purposes.  Vast amounts of energy and emissions will inevitably be produced during decommissioning which would also have a detrimental environmental impact.

There are many criticisms aimed at leaving the structures where they are. As per Greenpeace, "the sea is not a dustbin". In addition, some argue that taxpayers should not be subsidising enormous decommissioning costs and that all traces of the platforms should be removed.  Ideally, one would expect complete removal of the structure but the reality is that decommissioning itself can be very destructive for the environment.  There is no perfect solution or one that will satisfy everyone.

Reality requires a balancing of stakeholders? interests and a comprehensive appreciation of the potential environmental consequences of decommissioning on a case by case basis, especially in respect of older platforms.  Critical is a post-decommissioning regime for accountability, monitoring, pollution preparedness and mitigation strategies as well as ongoing technological development to further remove the inherent risk in a decommissioned platform.