With governments and industries around the world working to reduce carbon dioxide emissions, the clean energy sector is experiencing a boom. The UK’s wind and wave resource coupled with its mature offshore industry would seem to make it ideally suited to becoming a leader in clean energy expertise. Current notable projects include the Gwynt y MÔr offshore wind farm in North Wales and the Longannet Carbon Capture and Storage retrofi t.

 Offshore Carbon Capture and Storage (CCS)

The capture and storage of carbon dioxide gas deep underground as a means of mitigating the use of fossil fuels is a relatively new concept and one which is not specifi cally addressed by UK safety laws. Most CCS proposals involve the storage of carbon dioxide offshore in underground geological formations, such as depleted oil fi elds, gas fi elds and saline formations.

Carbon dioxide is already injected into some oil fi elds in North America, such as the Weyburn- Midale Carbon dioxide Project, albeit primarily for the purpose of Enhanced Oil Recovery (EOR). Statoil’s Sleipner West fi eld hosts the world’s fi rst offshore CCS installation, which has captured and stored around one million tonnes of carbon dioxide every year since 1996. In the UK, the Government’s Department for Energy and Climate Change (DECC) launched a CCS demonstration competition in 2007. Up to £1 billion was awarded in the October 2010 Spending Review for the capital costs of the fi rst demonstration project.

What are the Risks of CCS?

Like many energy technologies, CCS has major accident hazard potential and operators will need to ensure that suitable controls are in place to mitigate the risks.

The volume of carbon dioxide produced by CCS schemes makes transport as a gas impractical. It must instead be transported at high pressure as a ‘supercritical’ fl uid. This presents a new risk; when pressure is lost in a supercritical carbon dioxide system (e.g. if there is a break in containment), the volume of the supercritical carbon dioxide rises dramatically and its temperature falls to as low as -80C. At that temperature, particles of solid CO2 (also known as ‘dry ice’) form which can be expelled at high velocities, creating impact and cryogenic burn risks. The warming of the ejected dry ice may create a subsequent asphyxiation risk as it turns to gas. The extreme temperatures also pose a risk to asset integrity and HSE have emphasised the important of gas monitoring systems that are suffi ciently robust to withstand them.

Almost all existing knowledge regarding the behaviour of carbon dioxide at high pressures has been obtained from EOR operations and it is likely that future CCS projects will utilise higher pressures (upwards of 200 bar). HSE view the extreme properties of supercritical carbon dioxide as a signifi cant safety hurdle and are proposing that appropriate scale experiments be carried out to further our understanding of what happens during large-scale supercritical carbon dioxide releases.

In addition to the unique risks of pressurised carbon dioxide, existing risks associated with the energy industry will arise. For example, a range of organic amines and other chemicals are commonly used in carbon dioxide capture processes. These substances are well known to be hazardous to health and are already categorised under the Control of Substances Hazardous to Health Regulations 2002.

 What Health and Safety Laws Apply?

While HSE believe that some laws must be amended to take account of specifi c risks from CCS, they consider much of the current health and safety regime up to task. Most of the UK’s health and safety laws apply to offshore installations and wells by virtue of the Health and Safety at Work etc Act 1974 (Application Outside Great Britain) Order 2001.

Offshore Safety Case Regulations

Similarly, the Offshore Installations (Safety Case) Regulations 2005 require operators of Offshore Installations to submit safety cases. In a safety case, operators must describe management systems and show a systematic and structured approach to managing the major hazards on the installation. “Installation” in terms of the regulations extends to those used for the storage of gas in or under the shore or bed of relevant waters.

 Pipeline Safety Regulations

The Pipeline Safety Regulations apply to both onshore and offshore pipelines. Carbon dioxide is not currently classed as a “dangerous fl uid” in terms of the Pipeline Safety Regulations which means that the notifi cation and Major Accident Prevention requirements of the regulations do not apply. Similarly, carbon dioxide does not by itself fall under the Control of Major Accident Hazard Regulations (COMAH) 1999 or the Planning (Hazardous Substances) Regulations 1992, which apply onshore.

HSE recently consulted on the Pipeline Safety Regulations, noting that “the presence of carbon dioxide does not, by itself, trigger any of the major hazard legislation”. However, HSE stated in their response paper, which was published in the fi nal quarter of 2010, that “it is too early in the process of developing this new technology to legislate in this area and consequently [HSE] has taken the decision to postpone this amendment.” The Pipeline Safety Regulations are, however, applicable in the limited framework of the current UK CCS demonstration projects.

A Report to the North Sea Basin Task Force by BERR in 2008 noted that some existing pipelines may be suitable for lower-pressure transport of supercritical carbon dioxide when they become available following close of production from the gas fi elds they service.