Enzyme-Enhanced Carbon Capture and Storage Solutions in Basaltic Rock

Atmospheric concentrations of carbon dioxide are currently at their highest level in 800,000 years. Anthropogenic activity is causing global heating at a faster rate than anticipated signifying the need for rapid and large-scale reduction. To address this, the UK government committed to reducing greenhouse gas emissions by 80% by 2050 in the Climate Change Act. To reach the global target, we need to remove 190 billion tonnes per year by 2060 to keep global heating from pre-industrial levels to <1.5oC. Currently we are only removing 40 megatonnes a year globally. One option is long-term storage in rocks called basalt: one such project in Iceland (CarbFix) is already successfully running pilot projects. Significant innovation is required in order to adapt this technology to grow the necessary storage sites globally, including those in the UK.

This project will use a novel approach to identify if the enzyme, carbonic anhydrase, can enhance the process by which the carbon dioxide can be pumped into the rocks for storage. Carbonic Anhydrase is commonly found in living organisms, helping to keep them correctly functioning under different conditions, but it is not naturally found in the environment. This means that the high pressures, different forces and new environment may mean that they don’t work as effectively. Our hypothesis is that by adding carbonic anhydrase into the earth’s crust in basaltic rocks, we can drastically increase the rates at which carbon dioxide can react with elements in these rocks to ultimately form minerals called carbonates, which are stable. This reaction results in the carbon dioxide being effectively sucked out of the pumped material and stored in the carbonate minerals over very-long timescales. The mineralisation reaction occurs naturally, without requiring an enzyme boost, and has been shown to occur at the CarbFix project in Iceland in a geologically short timescale of less than 2 years. However, this is because the rocks on Iceland are naturally hot being an active volcanic area. Therefore, as most other basaltic host rocks are far cooler, the addition of an enzyme will be required, in particular for CCS in the United Kingdom. For this reason, this project will run a series of experiments on basalts using the enzyme to test this idea and assess the best approach for extending to tests in the field and eventual deployment in real-life plants. Globally, there are many other countries on all continents that contain similar rock formations.

The overarching question that the proposed research will address is: Can enzymes promote efficient carbon capture and storage through the enhanced generation of carbonate minerals, through co-injection of CO2 and enzyme mixtures into porous rock? To answer this, we have built a unique inter-disciplinary team from new research communities of biotechnologists and geologists, coupled with the innovation and impact skills to scale the technology.

Key to enhancing the potential for CCS in basalts is increasing the carbonate reaction rate by the use of enzymes, for which the kinetics need to be understood. The kinetics of fluid chemistry and reaction texture evolution depends on temperature and pressure, in part for standard reasons that reactions are thermally activated. In addition, though, the intrinsic stability and activity of enzymes depend on temperature (and perhaps on pressure). We have preliminary data that demonstrates the retention of CA activity after adsorption to Etna basalt and significantly enhanced activity in cross-linked enzyme-aggregates (CLEAs). Clearly, there is a need to investigate the ideal temperature and pressure "field' conditions for CA-mediated mineral carbonation in basalt.