Photo © Tom Kirsch, opacity.us
Kokerei Zollverein was constructed in Essen between 1957 to 1961, and processed rock from the adjacent Zeche Zollverein (colliery), transforming the coal into coke. Coke is a "pure" form of coal used as both a fuel and reducing agent by blast furnaces in iron production; the water, coal-gas and coal-tar are removed from the rock by baking it in large ovens.
When Kokerei Zollverein first opened, it had the capacity to process 5,000 tons of coke per day. When the number of furnaces was increased from 192 to 304, the plant reached a capacity of over 8,500 tons of coal a day, and it was considered the largest and most modern coking plant in Europe. The facility was designed by Fritz Schupp, whose most notable work was Zeche Zollverein's number 12 shaft - this Bauhaus-inspired winding tower not only became the archetype for future designs, but also became symbolic of both the Ruhr area and the entire German heavy mining industry.
The facility was closed in June 1993 due to the sharp decline in steel needs, and after an unsuccessful attempt to sell it to China plans were slated for demolition. It was saved from this fate by the Stiftung Industriedenkmalpflege und Geschichtskultur (Foundation for the Conservation of Industrial Monuments and Historical Culture). The site was listed as a UNESCO World Heritage Site on December 14, 2001. Although much of the area is disused, parts of the plant have been renovated to become home to a cafe and beer garden. The nearby colliery Zeche Zollverein has been almost completely renovated to be used by many different cultural businesses; more information can be found on their website http://www.zollverein.de.