We need to scrub CO2 from the air. There are two primary devices to perform this function on the ISS. On the Russian Segment there is воздух "Vozdukh" (literally translates as 'air') (located in the SM) and on the US Segment there is CDRA (Carbon Dioxide Removal Assembly) (located in the Lab). Both devices utilize the same principle. read more
Plants, algae, cyanobacteria and phytoplankton all split water molecules as part of photosynthesis -- the process that converts sunlight, carbon dioxide and water into sugars for food. The hydrogen is used for making sugars, and the oxygen is released into the atmosphere. read more