For the first time, virtual models for the sub-processes of paper production, from stock preparation to winding, and the energy supply systems are being compiled in an overall system as part of FOREST. The modular software framework forms the basis for digital twins of real paper machines. The link with machine and process data from ongoing operation makes it possible to visualize the actual state of the plant in detail and to create forecasts. This means that plant areas with high optimization potential can be identified during operation and changes in operation or conversions can be tested and evaluated before implementation.