Freshwater resources have faced serious threats in recent decades, primarily due to rapid population growth and climate change. Seawater desalination has emerged as an essential process to ensure a sustainable supply of freshwater to meet the global demand for freshwater. However, this approach has some shortcomings, such as the disposal of brines containing high levels of contaminants creating environmental problems, and the energy-intensive nature of desalination, primarily powered by fossil fuels, which contribute to greenhouse gas emissions. Consequently, as a solution, the zero liquid discharge approach has been identified by the body of research to be one of the viable methods to solve these problems. Over 90% of freshwater and reusable salts could be recovered through this approach. Adopting renewable energy-powered systems could make zero-liquid discharge desalination plants operate in an entirely environmentally friendly and sustainable manner. This review explores the integration of renewable energy-powered systems for the optimisation of seawater desalination treatment processes for zero-waste and improved productivity. The review also examines technologies and strategies that improve the efficiency and sustainability of desalination systems. By analysing recent research, we provide insights into the advancements, challenges, and prospects for optimizing renewable energy-powered seawater desalination processes aimed at achieving zero waste.

Globally, downstream petroleum operations face increasing pressure to optimize energy use and reduce carbon emissions, with electrically driven pumping systems representing the dominant site-level electricity load. This study investigates why anticipated energy savings from a variable frequency drive (VFD) retrofit were not realized in a Kenyan petroleum depot. High-resolution PLC-SCADA data at 1 s intervals were analysed over a six-month period using a custom Pump-Arm Modelling framework, reconstructing pump operation and energy consumption as a function of loading arm demand, runtime, and control mode. Results show that, despite VFD installation, pump speeds remained effectively fixed, and energy consumption was governed by discrete loading arm demand rather than speed modulation. Eight months billing data confirmed that post-retrofit energy intensity increased, from an average of 0.493 to 0.555 kWh/m³, demonstrating that expected efficiency improvements were not achieved. Stratified analysis further showed that idle running due to manual overrides accounted for approximately 3% of total depot electricity consumption. To contextualize this performance gap, idealized affinity-law scaling was applied to observed partial-load intervals, revealing unrealized energy savings potential of approximately 92 MWh, equivalent to a depot-level savings potential of 28.4% ± 1.4%. The findings indicate that limited energy savings were attributable to open-loop control architecture, partial digital integration, and legacy equipment constraints rather than VFD hardware limitations, highlighting the need for demand-aware, closed-loop energy optimization in retrofitted petroleum depots.