PEP piece of earthen pie A piece of earth cake. a cake, we eat it, it is big, useful, tasty. This is in my opinion very good synonym for the mining industry. in particular for the production of brown coal, which still is one of the main unsustainable energy sources on the planet. But the general trend is ok, mankind refuses unsustainable energy sources, in favor to use ecologically safe, renewable, sustainable such as solar, wind, geothermal energy etc. And it is the problem of reclamation of former industrial areas. Particular example - the former coalfields.