A recent report by the Organized Crime and Corruption Reporting Project, a venture backed by billionaire hedge fund manager and philanthropist, George Soros, furnished new documents to allege that in 2014, the Adani Group claimed ‘low grade’ coal, imported from Indonesia, to be ‘high-quality’ coal, inflated its value and sold it to Tamil Nadu’s power generation company, TANGEDCO (Tamil Nadu Generation and Distribution Company).

High and low quality are relative terms and only meaningful in the context of where the coal is used and how they are processed. The Gross Calorific Value (GCV), or the amount of heat or energy that can be generated from burning the coal, determines the gradation of coal. Coal being a fossil fuel is a mixture of carbon, ash, moisture and a host of other impurities. The higher the available carbon in a unit of coal, the greater is its quality or ‘grade.’ There are 17 grades of coal by this metric from grade 1, or top quality coal, with a kilo of it yielding higher than 7,000 kcal, and the lowest producing anywhere between 2,200-2,500 kcal, as per a classification by the Coal Ministry. However, the calorific value is not a useful metric on its own. The most important uses of coal are in running thermal power plants or powering a blast furnace to produce steel and both require different kinds of coal. ‘Coking’ coal is the kind needed to produce coke — an essential component of steel making — and thus requires minimal ash content. Non-coking coal, despite its ash content, can be used to generate enough useful heat to run a boiler and turbine.