The Black Truth: Part I
As we have already seen in the previous article, coal is one of the most important sources of electricity, not just in India, but in the entire world as well. Although renewable energy sources play a growing role in our energy mix, coal still dominates. Why is that so? How long has it been the case? How long can it continue? I will try to answer these questions in this and the following four articles titled “The Black Truth”.
Before we delve into the above-mentioned questions, we need to understand what coal is and how it is formed. As per Wikipedia, coal is “a combustible, black or brownish-black, sedimentary rock, usually occurring in rock strata in layers or veins called coal beds or coal seams.” Coal is a mineral of fossilized carbon. So it is primarily composed of carbon, but also contains varying quantities of other elements like hydrogen, sulfur, oxygen, and nitrogen.
How Was Coal Formed?
In the geological past, million sof years ago, the earth had dense forests in low-lying wetland areas, which were buried underneath soil due to natural processes such as flooding. As more and more soil was deposited over them, they sank deeper and deeper, thus getting exposed to higher and higher pressures and temperatures.
As the process continued, the plant matter was protected from bio-degradation and oxidation, and instead converted first to peat, then to lignite, then to sub-bituminous coal, then to bituminous coal, and then to anthracite. Hilt’s law states that “in a small area, the deeper the coal, the higher is its rank (or quality)”. This law is true if the temperature gradient is entirely vertical, but metamorphosis may cause lateral changes in rank, irrespective of depth.
The process of coal formation, needless to say and by definition, is very slow; it has taken millions of years for the world’s coal reserves to form, which is a timeframe that is difficult to comprehend. And we are well on our way to exhausting these reserves in the relatively very short time span of 300-400 years! If we don’t do something about it, all future generations will look at us the worst generation, which compromised their sustainability.
To be fair to us, we are also the ones who are inventing all the renewable energy technologies, but we have to do a much better job of it, if we want to avoid the curse of the future generations; the current pace of adoption just isn’t good enough. That is the context for this series of articles and everything happening today on the climate change front.
(Prashant Karhade is a guest author of ABC of Solar)