thumb|Kennecott Garfield Smelter Stack with its post 2023 paint scheme, February 2026
thumb|Aerial view of 1215-foot tall Garfield Smelter Stack, the north end of the [[Oquirrh Mountains and the Great Salt Lake, 2016|375px]]
Kennecott Utah Copper LLC’s Garfield Smelter Stack is a high smokestack west of Magna, Utah, alongside Interstate 80 near the Great Salt Lake. It was built to disperse exhaust gases from the Kennecott Utah Copper smelter at Garfield, Utah. It is the 61st-tallest freestanding structure in the world, the 4th-tallest chimney, and the tallest freestanding structure west of the Mississippi River.
Waste gases
The Garfield Smelter Stack was completed in 1974, replacing several earlier smokestacks, the tallest of which was high. The extra height was needed to meet the requirements of the Clean Air Act of 1970, to disperse waste gases according to new standards.
The off-gases from the flash smelting furnace contain 35–40% sulfur dioxide. They are cooled and cleaned in a waste-heat boiler, electrostatic precipitator and scrubbing system before being sent to the sulfuric acid plant. The acid plant produces either 94% or 98% sulfuric acid with tail gas containing typically 50–70 ppm sulfur dioxide, resulting in a measured sulfur fixation of greater than 99.9%. In 2006, the company produced and sold approximately of sulfuric acid, made from the formerly released gas. The acid recovery plant is designed to also recover waste heat from the process to produce electrical power. Approximately 24 MW of electrical power is generated, representing 70% of the smelter’s electrical requirements. equivalent to $ in .
The top can be accessed by a Swedish-built elevator that crawls up a gear track on the inside surface. It takes 20 minutes to ascend the stack, although workers only need to travel up to the 300-foot level each day, to service the air-sampling station.