This work addresses the optimum design of a phosphoric acid (PA) production process under uncertainty, both from an economic and environmental perspective. A design and optimization framework is employed that utilizes generic process modules to enable systematic process flowsheet development and to facilitate interconnectivity among the utilized processing components. This is coupled with a systematic method of incorporating uncertainty into the process design and optimization, hence, enabling a realistic representation of industrial conditions during the PA process design stages. The integrated design of PA production processes and downstream phosphogypsum utilization processes is further proposed, in the form of the Ammonium Sulfate (AS) production process, as a means of mitigating the environmental impact of the PA production process associated with phosphogypsum. The case studies, presented to illustrate the proposed developments, highlight the significant impact of considering uncertainties in the design of optimum PA process schemes as well as generate useful insights regarding the synergies developed in the integrated PA and AS process design.