Coal is still one of the most popular energy sources on the planet. Unfortunately, it is also one of the more polluting sources. Right now, coal is not a clean energy and most people would argue that that fact is unlikely to ever change. However, scientists are working behind the scenes to change the face of coal and make it a cleaner energy source.
Around 27% of all our primary energy needs are met by coal and nearly 40% of electricity is generated from coal. This shows the world’s dependence on this fuel source. But, coal is incredibly damaging to the environment and burning it releases around 14 billion tonnes of carbon dioxide into the atmosphere every year. The challenge experts face now is to create a method of burning coal without these pollutants being released.
The world has vast reserves of coal and we want to be able to continue to use them in order to power our daily lives. However, we cannot do so unless something changes in the way coal is burned or we will damage the world irreparably. The main technology that is being explored at the moment is called Carbon Capture and Sequestration (also known as Carbon Capture and Storage), which is abbreviated to CCS. The way CCS works is by capturing the carbon dioxide emissions as they are being emitted and before they are released into the atmosphere. The carbon dioxide is then stored 2-3km below the surface of the Earth and kept there permanently.
There are a number of different ways to capture carbon dioxide from gas streams, but none of them has yet been optimised to work with coal-burning power plants. They simply have not been built to function on that scale yet. When it comes to natural gas wells, carbon capture works well, whereas it is much more difficult to capture carbon released in flue gas streams as the concentration of carbon dioxide is low and the flue gas is hot. As for the sequestration of carbon dioxide, a range of methods exist, including injecting it into unmineable coal seams or saline aquifers, which are porous sedimentary rock deposits deep under the ground that are saturated with salty water and therefore unfit for human consumption or agricultural use.
The present trends we are seeing with regards to clean coal technologies include coal gasification. This process uses steam and oxygen to convert coal into ‘syngas’, a synthesis gas consisting of hydrogen and carbon monoxide. Then, instead of burning coal, it is used in this gas form, which is a far cleaner option. Rises in the price of natural gas has made this process more economically viable and it is something that is being explored extensively by researchers and developers.
One of the main problems that clean coal technology developers face is a lack of financial and political commitment. The cost of CCS is still very high and investors are unwilling to pour money into something that does not yet have clear and successful results. Therefore, commercialising clean coal and making it economically competitive is going to take a lot of innovation. However, as the battle against climate change continues and countries are forced to become more creative in order to meet emissions targets, it is likely we will see a greater interest in clean coal technologies.
