CCS experiment shows minimal environmental impact of CO2 leakage

Microscope Microscope Credit: clarita, MorgueFile

The Quantifying and Monitoring Potential Ecosystem Impacts of Geological Carbon Storage (QICS) project was led by Jerry Blackford of the Plymouth Marine Laboratory’s (PML) and funded by the Research Councils of the UK, the Natural Environment Research Council, and the Scottish and Japanese Governments. The experiment’s objective was to assess the impact of a real-life leakage on marine life on the seabed and in the water above, as well as to determine methods for detection and monitoring of a small-scale CO2 leak. Key conclusions of the research were that a small-scale leak would entail only limited environmental damage, restricted to a small area with quick recovery rates of both the chemistry and biology.

Bellona Europa finds the results of this experiment encouraging and welcomes the recommendations it provides for CCS operators engaged in developing risk strategies, namely: CCS site selection should be below dynamic bodies of water to promote dispersal of CO2 in the unlikely event of leakage; a comprehensive baseline assessment, encompassing sediment structure and content, sea water chemistry, biological community structure and ambient noise, is required to maximise monitoring efficiency; and a combination of chemical pH and bubble-listening sensors will maximise early leakage detection or alternatively provide assurance that leakage is not occurring.

For the purposes of the experiment, 4.2 tonnes of CO2 were 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. Scientists initially monitored how the CO2 moved through the sediment and the 12 meters of water above. For the duration of one year, the impact of the leaked COon 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. A combination of these techniques are claimed to offer the optimal monitoring technology for detecting leakage and assurance of its absence.

This simulated leak demonstrated that the impact of a CCS-related CO2 leakage of similar scale would be limited. The chemical changes observed as a result of the CO2 ­leak returned to background levels within 17 days of turning off the CO release. With regards to the biological effect, no changes were observed during the early stages of the leak. A change in seabed-dwelling communities as well as the gene expression of microbes was observed at the end of leakage period and in the early recovery period. These were, however, not long lasting and full recovery was achieved within weeks.

Project Leader Jerry Blackford said “These findings are contributing to the growing knowledge base necessary for optimal deployment of CCS as a climate change mitigation measure; in particular for the regulatory requirement for monitoring. The results show that small-scale leakage will not be catastrophic, although we do caution that impacts are likely to increase if a larger amount of CO2 is released. Water movement in the area is also important; impacts are estimated to be less and recovery quicker in environments with stronger water mixing so that the CO2 is dispersed more rapidly”.

To read more about the project click here.