The paint shops of the East Bavarian BMW Group plants in Dingolfing and Regensburg will be completely converted to dry separation with limestone flour in the near future. In Dingolfing, all four painting lines have already been converted. At the Regensburg plant, the first of two lines will start at the beginning of 2024, before the second one follows in August 2025.

The new process saves 17 million liters of water and around 17,400 megawatt hours of energy every year. This reduces CO₂ emissions by more than 5,000 tons.

The paint shop in Dingolfing is the first in the company’s worldwide production network to completely change to the new painting process of dry separation with limestone flour. Within two years, it was possible to convert all four painting lines during the production process. The changeover is currently underway at the Regensburg plant: One of a total of two base paint lines will be rebuilt and put into operation by mid-January 2024. The conversion of the second line to dry separation is planned for August 2025.

The limestone flour used as a binder is recycled after use and reused in the building materials industry.

Limestone flour is used in the East Bavarian BMW Group plants in Dingolfing and Regensburg as a binder in the paint shop to catch paint overspray.

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This has a significant influence on the carbon footprint of both plants, as painting is the most energy-intensive production process in vehicle construction.

All converted paint lines use a system for the dry separation of paint particles that works with limestone flour as a binder. Paint mist which does not land on the body—i.e., the overspray—is caught with stone flour instead of water as before. This significantly reduces water consumption. In Dingolfing, four million liters of water are saved per year, in Regensburg 13 million liters of water.

80% of dry separation takes place in recirculation mode, unlike the previous procedure with Nassau washing. Thus, no longer 100%, but only 20% of the air has to be tempered and humidified. Specifically, in Dingolfing, the heating energy demand is reduced by 13,000 megawatt hours per year and thus the annual CO₂ emissions by more than 4,000 tons. The Regensburg plant consumes 4,400 megawatt hours of energy in the form of natural gas less annually and thus avoids about 1,150 tons of CO₂.

The third advantage of the new painting system is that the limestone flour does not have to be treated and disposed of like contaminated wastewater, but is returned to the recycling cycle.

The limestone flour comes from the region—it is Walhalla Kalk, which is mined at the foot of the Keilberg near Regensburg. In Dingolfing, an average of three trucks currently deliver the fresh mineral material per week, in Regensburg one to two trucks. It is then filled into huge silos. From there, it enters the paint booths dust-free and safely via pipelines.

The paint shops use about 20 kilograms of stone flour per vehicle as a binder and then feed the stone flour-paint mixture into the recycling cycle via regional disposal companies. Among other things, it serves as a raw material for cement.