DIRTY LITTLE SECRET: Coal Is Fueling Bitcoin’s Meteoric Rise.

Eight 100-meter-long metal warehouses in northern China are a case in point. Bitmain Technologies Ltd. runs a server farm in Erdors, Inner Mongolia, with about 25,000 computers dedicated to solving the encrypted calculations that generate each bitcoin. The entire operation runs on electricity produced with coal, as do a growing number of cryptocurrency “mines” popping up in China.

The global industry’s power use already may equal 3 million U.S. homes, topping the individual consumption of 159 countries, according to the Digiconomist Bitcoin Energy Consumption Index. As more bitcoin is created, the difficulty rate of token-generating calculations increases, as does the need for electricity.

“This has become a dirty thing to produce,” said Christopher Chapman, a London-based analyst at Citigroup Inc.

Where’s the outcry from Silicon Valley?