Waste-to-Energy (WtE) plant development is a milestone in the pursuit of integrated waste management and renewable energy production. As waste generation globally is on the rise in tandem with the demand for cleaner energy, WtE systems offer a dual advantage: alleviating landfill pressure and also recovering valuable energy resources. However, the effectiveness of traditional WtE plants has consistently been constrained by inefficiencies created through manual processes, inconsistent feedstock quality, and rigid control systems. In this regard, new process optimization and control technologies have emerged as breakthrough technologies for reimagining the operational and environmental performances of WtE plants. By applying smart automation, real-time data analytics, and predictive simulations, these technologies allow plants to adapt dynamically to changes in waste composition, burning parameters, and grid loads. Techniques such as Model Predictive Control (MPC), Supervisory Control and Data Acquisition (SCADA), Artificial Intelligence (AI), and adaptive feedback control loops are currently being applied to WtE plants to gain maximum energy production, minimum emission of pollutants, and lower operation cost. This paper presents a comprehensive overview of these technologies and their implementation across the globe's WtE facilities. The increasing contributions of Internet of Things (IoT) connectivity, Digital Twin simulation, and Cyber-Physical Systems (CPS) towards enabling closed-loop, autonomous operation are addressed. Case studies are included to show performance enhancement in energy efficiency, environmental compliance, and resource optimization. Moreover, the paper also evaluates major challenges including integration complexity, data quality issues, cybersecurity threats, and the need to upskill the workforce. Finally, this research offers actionable recommendations to plant operators, policymakers, technology suppliers, and researchers in collaboration to drive the next generation of intelligent WtE plants. As part of the overall move towards circular economy models, the adoption of advanced process optimization will be essential to maintaining WtE plants healthy, compliant, and financially sound in the midst of evolving environmental and regulatory landscapes.