Strategies for collecting water from the atmosphere using minimal energy could fill a crucial gap in sustaining communities that have limited access to water.
By Michael Eisenstein
A creative illustration of a scientist squeezing water out of the sky.
Illustration: Sam Falconer
In late summer, Death Valley National Park earns its name. The heat in this region of California and Nevada is relentless. Record temperatures are set, and the air is often bone dry. The 22 August 2022 was no exception, with an average temperature during daytime of 51.6 °C and humidity of just 14% in the location aptly known as Furnace Creek.
Despite the heat and aridity, there was a slow but steady drip of water into the collection vial of Omar Yaghi’s device, an assembly of components loosely resembling a telescope. By the end of the day, this system had collected only a few millilitres of water — barely enough for a refreshing sip. But these results, published in July1, nevertheless represent a landmark in the field of atmospheric water harvesting (AWH).
Given the extremity of the testing conditions, the results suggest that the key ingredient in this device — a water-absorbing compound called MOF-303 — has the potential to deliver life-sustaining volumes of clean water to regions that currently struggle to access it. “The vision there is to have something like a village-scale device,” says Yaghi, a chemist at the University of California, Berkeley. “If you’ve got a tonne of MOF-303, you could deliver about 500 litres of water a day, every day for five to six years.”
By current estimates, roughly two billion people lack access to clean drinking water. Desalinated seawater can meet some of this need, but the technology required remains costly and is limited to communities with coastal access. This explains the growing enthusiasm for alternative solutions that extract clean water from the air. The US Geological Survey estimates that Earth’s atmosphere contains nearly 13,000 cubic kilometres of water — more than six times the volume of the world’s rivers. “You cannot deplete it — it’s always replenished by natural evaporation from a larger water body,” says Tian Li, a materials scientist at Purdue University in West Lafayette, Indiana. And although many of the most promising AWH technologies are still at the stage of lab demonstrations or proof-of-concept devices, the field is quickly building momentum towards real-world systems that produce plentiful amounts of water at low cost.
Searching for suitable sorbents
There are already several commercially available AWH systems. In mountainous, foggy regions, it is possible to literally cast a net to collect water from ever-shifting cloud masses. Such installations are producing water from the air in South America, India and parts of Africa, according to Thomas Schutzius, a mechanical engineer at the University of California, Berkeley. There are also systems for collecting the water that accumulates overnight as dew. But both fog and dew harvesting are limited to high-humidity areas. And for dew, only modest volumes of water can be produced even under optimal conditions.