A method for a plant-wide optimization process comprising continuous conversion of raw ingredients into intermediate components and non-continuous conversion of the intermediate components into desired products, the method for the plant-wide optimization process comprising: a master model predictive controller receiving constraints on raw ingredients available for use during a period of time; the master MPC controller receiving constraints on the intermediate components, wherein the intermediate components produced during the period of time based at least in part on one or more of the constraints on raw ingredients and inventory storage constraints for the intermediate components; characterized in that the constraints on the intermediate components include a lower production limit for a particular intermediate component as well as an upper production limit for that particular intermediate component; the master MPC controller receiving information on desired products to be produced from the intermediate components produced during the period of time, where production of the desired products from the intermediate components is governed at least in part by recipes that specify how the intermediate components are combined to form the desired products; the master MPC controller receiving proxy limit values from each of one or more slave MPC controllers, where each of the proxy limit values identifies to what extent one or more process variables controlled by the corresponding slave MPC controller are adjustable, the proxy limit values identify a minimum value or a maximum value obtainable for the one or more process variable without violating any process variable constraints; and the master MPC controller performing the plant-wide optimization that includes the continuous conversion of raw ingredients into intermediate components as well as a non-continuous production of the desired products from the intermediate components, wherein the proxy limit values allow the master MPC controller to honor the process variable constraints of the one or more slave MPC controllers during the plant-wide optimization. a master model predictive controller receiving constraints on raw ingredients available for use during a period of time; the master MPC controller receiving constraints on the intermediate components, wherein the intermediate components produced during the period of time based at least in part on one or more of the constraints on raw ingredients and inventory storage constraints for the intermediate components; characterized in that the constraints on the intermediate components include a lower production limit for a particular intermediate component as well as an upper production limit for that particular intermediate component; the master MPC controller receiving information on desired products to be produced from the intermediate components produced during the period of time, where production of the desired products from the intermediate components is governed at least in part by recipes that specify how the intermediate components are combined to form the desired products; the master MPC controller receiving proxy limit values from each of one or more slave MPC controllers, where each of the proxy limit values identifies to what extent one or more process variables controlled by the corresponding slave MPC controller are adjustable, the proxy limit values identify a minimum value or a maximum value obtainable for the one or more process variable without violating any process variable constraints; and the master MPC controller performing the plant-wide optimization that includes the continuous conversion of raw ingredients into intermediate components as well as a non-continuous production of the desired products from the intermediate components, wherein the proxy limit values allow the master MPC controller to honor the process variable constraints of the one or more slave MPC controllers during the plant-wide optimization.