CO2 Utilisation gaining potency

Carbon Dioxide

Despite the progress being made – especially in the US, Canada and China – CCS remains an expensive technology, both to install and to operate. One way to mitigate this is to treat the ‘waste’ product, the CO2, more as a commodity. The US FutureGen project aims to upgrade an Illinois coal fired power plant with CCS, read more here)It began in 2003, was put on ice due to high costs, but is being revived as FutureGen 2.0. This time around the project is looking to use COto generate power.

An article describes how researchers are looking into using CO2 as a ‘geofluid’. It would be used to extract heat from geothermal site, by sending CO2 underground to absorb to geothermal heat before being sent back up again, by which temperature it can then be used to run a power plant.

Using CO2 instead of water to draw up the heat will offer three distinct advantages. First of all, supercritical CO2transfers heat more easily though porous rocks than water due to its liquid-like density but gas-like viscosity. Second, supercritical COis more buoyant than water and therefore does not require pumps to rise to the surface. Third, CO2turbines are more efficient than water turbines.

Although these three factors would all in theory improve the efficiency of a power plant, so far only computer simulations have been made.

Other uses for COinclude Enhanced Oil and Gas Recovery (EOR and EGR), whereby injection of CO2 underground increases the pressure in oil and gas fields so that the flow and extraction rate increase. This has especial relevance to older fields or those nearing depletion, to make sure that they are at least used for their full potential rather than being closed prematurely and being replaced by the opening of new fields.

These kind of activities can improve the business case for CCS. Scepticism has been expressed in some cases, in particular regarding EOR/EGR and the issue of enabling more fossil fuel use when we should be reducing. However, the condition of these applications is of course capture and eventual storage, thereby cutting emissions.

Joanna Ciesielska