The Autonomous Low Energy Replenishment Dredger (ALERD) strives to revolutionize the dredging world. The ALERD operates autonomously underwater, which saves energy during the dredging process and transit. Autonomous underwater operation drives the need of alternative energy facilities. However, due to the energy savings of dredging, alternative energy supplies are possible. A wish of C-Job is that the ALERD operates with zero emissions, and therefore the system should comply with it as well. This introduces the research goal: Devising a sustainable electrical energy supply for ALERD. An additional challenge to the research goal is that the dimensions are not yet established and are still an open question in the research. The simulation model uses the calculated electric load balance of the Autonomous Underwater Maintenance Dredger (AUMD) and scaling to determine the power balance of the ALERD over various hopper volumes. Furthermore, the operational area has been studied to determine charging/bunker locations and distances. The project requires an annual sedimentation of 12 million m³, including foreshore and coastal replenishment. To determine the best system, a literature review was done towards the systems. Two key systems came out as the best systems for autonomous and sustainable operation: The Li-ion battery and the Proton Exchange Membrane Fuel Cell (PEMFC). The systems have very different characteristics. Typically, batteries have high costs for the energy storage and fuel cells costs are determined by the nominal power output. The abovementioned systems were both used in a simulated operational profile of the ALERD. Results from the simulation, suggests that the battery has the optimal performance at 2-3 times dredging per energy cycle, where 4-9 times are the optima for the Hybrid solution. When both systems have charging/bunker stations near the operational area, a dredging cost of €*** per m³ can be achieved for both systems. However, when the ship is charging/bunkering in the port, the costs per m³ increase with €*** for the hybrid and €*** for the battery powered ALERD. This results in a maximal investment of €** million for a local charging/bunker station, to be economically feasible. By making these stations accessible for other purposes, profit can be taken to recoup the investment. It is however expected, that these local stations will not be feasible for the first generation of ALERDs. When cost development is taken into account, the Total Cost of Ownership (TCO) prefers the hybrid system. Which is a result from the sharply decreasing hydrogen and fuel cell costs. The system also achieves a lower TCO than a conventional dredger, in a manageable time. A (near) future orientated system has also been considered, the direct-fed ammonia Solid Oxide Fuel Cell (SOFC). It has comparable costs per cubic metre for port bunkering as the other systems, when they are locally charging/bunkering. Furthermore, there are a lot of practical advantages by the use of ammonia instead of hydrogen as fuel. This consists of better fuel handling and easier storage. Together with the benefits of taking more energy inside the ALERD, it is believed that the hybrid types of ALERD have the best characteristics for coastal maintenance. It depends on the developments of the ammonia SOFC, if it is ready to supply energy to the ALERD, or that the hydrogen PEMFC is the best solution in a hybrid design. Furthermore, the decision depends on the results of the weight and stability study, which is still ongoing. The results could eliminate a systems by its volume or weight. Due to the reserved space and freedom in the ship design, this is however not expected.