S&P said June quarter exports were about level with the March quarter at 23.2Mt, but down on the 28.3Mt shipped 2018 Q2. Exports to India were down 24.6% yoy.

"We are shipping coal everywhere that we can find a home for it. I mean, we're moving coal into South America. We're moving coal into Asia. We're still moving coal into Europe," Foresight Energy LP CEO Robert Moore said recently.

"The netbacks on export tons are falling compared to the levels seen before and the company is evaluating options to move coal back into domestic markets."

But CEO of Illinois Basin producer Alliance Resource Partners, Joe Craft said he wasn't "counting on the domestic market mix changing and I'm not counting on the domestic market growing".

New York investment bank Jefferies said this month US electricity generation was likely to "grow very slowly at best, and there are no coal-fired power plants being planned or under construction in the US".

"Furthermore, natural gas prices are at low-points, squeezing coal's market share in US power generation; the affordability of renewables is doing the same.

"ESG is a serious consideration in public discourse and becoming increasingly important in the investment community."