The biowaste methanization plant in Kirchstockach is operating successfully since 20 years.

As the plant was operating at about 150% of its original design capacity, the anaerobic digestion step – the bottleneck of the installation - was extended in 2010/2011 by a third hydrolysis tank.

The plant is based on two-stage wet anaerobic digestion process. The organic suspension, previously cleaned in the BTA® Hydromechanical Pre-treatment, is separated into a solid and a liquid phase. The liquid phase with a high amount of already dissolved organic material is pumped directly into the fixed film methane reactor. The dewatered solids are mixed with recirculated process water and fed into the hydrolysis tanks to dissolve the remaining organic solids. After 2-4 days, the suspension is dewatered and the liquid is also fed into the methane reactor.

The produced biogas is converted into heat and power in two CHP units (with ca. 330 kW_electric each). It is planned to install a third unit to increase the installed electrical capacity to 1 MW.    

While the liquid phase is widely recycled in the process and the remaining amounts are treated in an internal effluent treatment plant, the resulting solid hydrolysis residue, contaminant free and low in salts, is further stabilized in the plant’s existing composting facility together with green waste.