Annual cost savings for energy supply and waste disposal were 63% and decreased from 1.4 Mio € to about 0.5 Mio €. The calculated payback period of the total investment is 9 years. Beside the economic benefits, which is the most relevant decision criterion, the positive environmental impact should also be highlighted: a 79% reduction of greenhouse gas emissions from 4.5 Mio kg CO2 to 0.9 Mio kg CO2 annually was achieved