Following a novel series of experiments carried out beneath the waters of a Scottish sea loch, a team of scientists led by PML have concluded that small-scale leaks from sub-seabed carbon dioxide storage are likely to have little effect on local marine life.
Carbon dioxide capture and storage (CCS) has been identified as one way of reducing the amount of carbon dioxide (CO2), resulting from the burning of fossil fuels and other industrial processes. Simply, CO2 is captured at source, transported via pipelines and then injected into geological strata a kilometre or more underground. Offshore depleted oil and gas reservoirs and natural saline aquifers are potentially ideal sites for such storage and experience suggests that storage will be robust. However, there are natural concerns about what might happen if there is a leak and how best to design monitoring systems to ensure that leakage is not occurring and detect it if it should happen.
The Quantifying and Monitoring Potential Ecosystem Impacts of Geological Carbon Storage (QICS) project, led by PML’s Jerry Blackford and funded by the Research Councils UK, the Natural Environment Research Council, the Scottish and Japanese Governments, set out to investigate and answer these concerns. A number of UK and Japanese institutes collaborated with the experimental controlled release of CO2 undertaken in Ardmucknish Bay, (near Oban) Scotland in 2012; the experiment was co-ordinated by the Scottish Association for Marine Science (SAMS). The project was a scientific success and was fully embraced by the local residents, without whose support the project could not have gone ahead.
4.2 tonnes of CO2 (less than the annual CO2 emission of a gas-heated UK home) was injected over 37 days from a land-based lab via a borehole drilled through rock to the release site, 350 meters from the shore and 11 meters below the seabed (see illustration below). Scientists initially monitored how the CO2 moved through the sediment and the 12 meters of water above. Over the following 12 months the impact on the chemistry and biology of the surrounding area was assessed using a combination of techniques, including chemical sensors, listening for bubbles and diver-mediated sampling.