World-first experiment on carbon-capture completes first stage

Jun 30, 2012 by Journal of Marine Science

The critical stage of a world-first experiment, to monitor what might happen if CO2 leaks from an underground storage reservoir, has been successful.

Following a complex drilling operation, the injection of CO2  from a shore-based laboratory into shallow marine sediments is allowing scientists to determine whether (and how) such a leak from a CCS sub seabed storage site would adversely affect marine life. The experiment is also enabling the assessment of various ways of monitoring for CO2 leakage.

As the world searches for viable climate change mitigation strategies, the approach of Carbon Capture and Storage (CCS) is one such method that is attracting significant international attention and is emerging as one of the frontrunners for tackling climate change. CCS is the process by which CO2 is captured, from power plants and industrial actions, before it is emitted into the atmosphere and then pumped into deep sub-seabed reservoirs / geological structures for permanent storing. The risk of leakage from storage sites is thought to be low, however, it is vitally important to thoroughly investigate the benefits and risks of potential mitigation strategies early in their development.

One such research project is the Quantifying and Monitoring Potential Ecosystem Impacts of Geological Carbon Storage (QICS), funded by RCUK / NERC and led by Plymouth Marine Laboratory in collaboration with the Scottish Association for Marine Science and four other institutions. The project’s primary experiment is a world-first and has been releasing moderate levels of CO2 into shallow sediments in a Scottish Bay, enabling scientists to study the progress and effects of a controlled CO2 leak and extrapolate these to real-life situations, which might occur in the future.

For the last 30 days CO2 has been supplied from a “pop-up” lab and travelled through a borehole under the sediment to the release site, 350 metres from the shore and 12 meters below the seabed of Ardmucknish Bay near Oban. Initial results have shown that the first two phases of the project (construction and CO2 release) have been successful and that the CO2 “behaved” as expected. Localised impacts had been anticipated and divers visiting the site have observed that some creatures are affected while others remain unaffected.

The QICS project leader, Jerry Blackford from Plymouth Marine Laboratory, said: “The experiment is going exactly to plan and we are very pleased so far. We are now at the stage of collecting detailed data which will enable us to get closer to predicting what might happen if a real leak occurred on an active storage site. As well as looking for environmental impacts the experiment has allowed us to test a range of monitoring equipment in a real world setting.”

The coordinator for this experiment, Dr Henrik Stahl from the Scottish Association for Marine Science, commented: “CO2 gas has been bubbling out of the sediments over the last few weeks and we have seen a clear but localised drop of the pH in the sediments and overlying water in the bubble zone, as expected. This drop is due to the CO2 reacting with the seawater, which alters the chemistry of the surrounding water and sediments, and therefore, reduces the pH. Some animals, such as sea-urchins living in the sediments, seem to react negatively to the increase in CO2 whereas others, such as crabs, seem to be attracted or unaffected by the bubbles; so there could be both winners and losers in a reallife situation. The next step is to turn off the gas flow and continue to study the recovery of the affected area.”

“Even though only a very small area of seabed is being temporarily affected by this experiment, we are confident that it will provide valuable information to help understand the implications of CO2 for marine life, should a leak occur elsewhere.” Although the gas injection has now been turned off, the site will continue to be monitored until at least September and scientists are confident that ongoing monitoring and analysis will prove essential in furthering the understanding of how leaked CO2 will move through sediment and how ecosystems will respond.