Alternate Environmental Control and Life Support System (ECLSS) technologies were evaluated to reduce Space Station resources and dependence on expendables resupplied from Earth to sustain a multiperson crew in low-Earth orbit. Options were evaluated to close the oxygen (O2) loop by removing carbon dioxide (CO2) from the cabin air, reducing the CO2 to water, and electrolyzing the water to provide metabolic O2 for crew consumption. Options were also evaluated to close the urine/flush, condensate, and hygiene water loops to provide potable water for crew use. Specific evaluation parameters were derived which included weight, power, volume, maintenance, resupply consumables, and technology readiness. The potential for significant resource reductions were indicated by modifying the Space Station ECLSS baseline to replace the cabin air CO2 removal unit with a move efficient process, adding a hydrogenation process for CO2 reduction, and adding an electrolysis unit to produce O2 for the crew. Further potential resource reductions were indicated by replacing the urine/flush water recovery unit with an ultra-efficient distillation unit. The ultra-efficient distillation unit has the potential to operate on Space Station waste heat and provide the water recovery subsystem with essentially 100 percent water recovery. The advantages of providing ECLSS technologies for the Space Station, which also could be used for human interplanetary missions, are addressed.