NOVELTY - The process comprises generating electrical power by an electrical power supplying unit, storing the electrical power in an electrical power storage unit, supplying the electricity for pumping water source and/or waste water source to a hydrogen fuel electrolyzer while level of the water source and/or waste water source within the electrolyzer and a pump (3) is controlled by a buoyant water level controller, and electrolyzing the water source and/or waste water source in a presence of a catalyst solution having 2-6% v/v% for 0.03-60 hours to produce a hydrogen gas fuel.    USE - The process is useful for: producing a hydrogen gas fuel from water source and/or waste water source (claimed) such as rain water, river water, seawater, tap water, sewage and leachate; and treating the wastewater, where the hydrogen gas fuel is useful as potential fuel for fuelling incinerator, internal combustion engine, thermal electric power generation, furnaces, heaters and cooking stoves.    ADVANTAGE - The process: improves the quality of the electrolyzed wastewater (sewage) within 3 hours; efficiently and economically produces highly clean, sustainable and environmental friendly hydrogen fuel source with high flammability and less energy consumption. The chemical oxygen demand of the wastewater can be reduced to 88%, suspended solids can be removed to 91% and 5-day biochemical oxygen demand can be removed to 87%.    DETAILED DESCRIPTION - The process comprises generating electrical power by an electrical power supplying unit, storing the electrical power in an electrical power storage unit, supplying the electricity for pumping water source and/or waste water source to a hydrogen fuel electrolyzer while level of the water source and/or waste water source within the electrolyzer and a pump (3) is controlled by a buoyant water level controller, and electrolyzing the water source and/or waste water source in a presence of a catalyst solution having 2-6% v/v% for 0.03-60 hours to produce a hydrogen gas fuel. The hydrogen gas fuel is supplied to intended users via pipeline distribution. The pipeline is provided with a flash back retarder (6).    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of a system to produce hydrogen gas fuel.    Photovoltaic collector (1)    Battery (2)    Pump (3)    Flash back retarder (6)    Wind turbine assembly. (9)