In rural Millard County southwest of Salt Lake City, a company is planning to install more than 400 natural gas-fired engines to produce power for a 4,000-acre data center.

Joule Capital Partners is seeking air permits for six power plants in what are currently farm fields. Initial plans call for each of the six plants to include powered by 69 Caterpillar generators, according to the Salt Lake Tribune – comparable to 400 semi-trucks idling.

Combined, these power plants could emit up to 5.2 million tons per year of greenhouse gases, roughly equivalent to more than 1 million cars and trucks driven for a year. They could also emit more than 4,100 tons per year of health-harming “criteria” pollutants that form smog and soot.