All air, from arid deserts to humid cities, contains water vapour – globally, an estimated 3,100 cubic miles (12,900 cubic kilometres) of water is suspended as humidity in the air around us. That’s more than all the water in Lake Superior, the largest lake in North America (11,600 cubic km), or five Lake Victoria’s (Africa’s great lake, at 2,700 cubic km). Or a whopping 418 times the volume of Loch Ness.
But we’re not talking about clouds. This is the humidity in the air we breathe, that reappears as beads of water on the side of a cold drink, or as morning dew on blades of grass. And a technological race is underway to harvest it as drinking water. If the emerging ‘water from air’ (WFA) devices can crack it, it could go a long way towards solving the world’s freshwater problem.
By 2025, two-thirds of the world’s (rapidly growing) population are projected to be living in conditions of severe water stress. Already, 2.1 billion people live without clean drinking water. The world’s poorest are being overcharged for water they know to be unsafe, but have no other option but to drink. Contaminated drinking water causes half a million deaths from diarrhoea each year. While in richer countries – which consume more water than poorer nations, due to intensive agriculture and industry – water from underground aquafers and river basins are being depleted faster than they are being replenished.