The US Department of Energy is to fund three new research projects that will investigate the feasibility of carbon sequestration – the capture and storage of greenhouse gases that otherwise would be expelled from energy facilities.
The first project, if successful, could significantly reduce the high costs and severe energy penalties that have hindered past approaches to sequestration. The other two projects will explore ways to store carbon dioxide safely and essentially permanently, again without imposing excessive costs on the consumer.
At the University of Texas at Austin, researchers in the University’s Department of Chemical Engineering will develop an alternative solvent that captures more carbon dioxide while using 25 to 50% less energy than conventional, state-of-the-art MEA (monoethanol amine) scrubbing, another CO2-removal method.
Using less energy allows coal plants to produce more electricity while capturing and storing CO2. By expanding on bench-scale system modelling and pilot-scale experiments, the university will develop and validate a process model to optimise solvent rate, stripper pressure and other parameters.
The second project involves researchers at the University of Massachusetts who propose to study a deep-ocean CO2-sequestration method that blends liquid CO2, water and finely ground limestone into an emulsion that could be pumped into the ocean for long-term storage. Because this emulsion would weigh more than seawater, it would sink to the deep ocean. This would make it possible to deposit CO2 at shallower depths than current directed-injection techniques. Soluble calcium bicarbonate, food for aquatic organisms, would be formed and stored in the ocean indefinitely. The emulsion will be analysed in-situ through windows to study its structure, droplet size and stability for one year. In the second year, an emulsion of liquid CO2, water and a possibly a surfactant will be investigated as it flows through a pipe.
The optimal mix of reagents to produce a stable emulsion will then be determined.
Lastly, researchers at the University of Kentucky Research Foundation in Lexington propose to displace natural gas from black Devonian shales and use these organic-rich rocks to store CO2.
Studies have shown that CO2 is preferentially adsorbed by gaseous coals in deep, unminable coal seams in very much the same manner that gas is naturally stored in these coals. In fact, CO2 displaces methane molecules two to one.
The study will determine whether a similar phenomena takes place in Devonian black shales, which serve as both a source and a trap for natural gas. The project will analyse CO2 adsorption along with natural gas production, and determine which shales offer the best sequestration potential. At the end of the project, data will be available through publications and Web-based systems.