CCUS: A CO2 economy

Moving CO₂ from the air to Lithos and converting it to useful products

One of the primary concerns of the current times is the increasing amount of carbon dioxide that is continuously accumulating in the atmosphere at an exponentially increasing rate. Every second, over a million kilograms of CO2 are released into the air through the burning of fossil fuels and from industrial processes. This isn't something completely new; we've been listening to this for several decades now. The so-called problem that researchers are trying to solve is to capture this carbon dioxide, store it somewhere, probably in a place that wouldn't increase the Earth's temperature, or utilize it in making something useful and less harmful.

The storage part is quite interesting. It came to me as a complete shock when I first heard of it. The way it's been done is like this: Industries in which huge carbon dioxide emissions occur are equipped with the CO2 storage system. The released CO2 is recaptured and transferred underground through an inlet. It is taken up to a distance, say 1-2 km. The CO2 gets stored in a region containing porous rocks filled with salty waters (Saline Aquifers) in the Earth's crust. This can be thought of as a mimic of a scenario in the underground environment in which natural gas and oil, the major fossil fuels, were trapped, formed, and stored for millions of years to manifest into the forms in which we use them. These, when burnt, produce a tremendous amount of both energy as well as emissions. The CO2 that is sent beneath through pipes gets trapped and stored in these rocks, awaiting its slow mineralization over the years. So, to cut a long story short, researchers are trying to put CO2 back to its original source. To some extent, it could be said that we are actually walking on a mass of slightly liquified CO2 that would be mineralized after several years from now. 

Carbon dioxide utilization is another area. This does not involve capturing and storing CO2 underground, but it does involve converting it into economically valuable products. In this, CO2 molecules undergo reduction to form methanol and further to methane. Methanol is a useful industrial raw material to produce chemicals like formaldehyde, acetic acid, plastics, fuels, paints, and feedstock. Similarly, methane is a crucial fuel. It's very similar to a circular economy, wherein you are able to get the same product again, like making use of waste plastic material to make a new one. This one could be thought of as a CO2 economy. CO2 is also used in several organic chemistry transformations to produce compounds such as cyclic carbamates. Controlled amounts of CO2 gases are purged into the reactant mixtures at specific pressure and temperature conditions to get the desired products.

All these technologies actually help in reducing the carbon footprint, as the CO2 is either being utilized and becoming a part of a product, it is being stored in a manner that reduces its atmospheric impact, or it is being converted into another, less troublesome form. These are among the most crucial technologies currently to control and check the emissions, as that's probably the only alternative we are left with. Of course, the best way to control is to reduce, and that's far from happening-as of now.

©Neha Kanase