Within the scope of hydrothermal carbonization, biomass is converted to bio-coal and other products. Because biomass occurs at irregular intervals at different locations and also, in part, only individual method steps are required at different locations, however, an apparatus for treatment of biomass is integrated into a variable, mobile container, and mobile containers adapted to the individual steps of the method are provided, which can be transported in compact manner and can be adapted, in terms of size, in the setup situation. This arrangement allows effective equipping of the individual containers, which can be expanded into a setup situation on location.