Atmospheric water harvesting: Our one environmental chance against a water crisis

Water is the essence of life, but it depends on what kind of water we are talking about. Approximately seventy percent of Earth’s surface is submerged in water, and only less than two percent of that water is drinkable and accessible to us. Sadly, we excessively waste this small portion on many activities, such as leaving the tap open, flushing toilets, showering for hours, and water balloon fights. But what happens when we run out of fresh water? Only catastrophes. Droughts will strike the most fruitful farms, turning them into scorching deserts. Chaos will spread across countries, and water will be the most valuable resource, more precious than oil. Telling the world to reduce its consumption of water would be too late at this instance. The only way to find fresh water at that point would be by extracting it from the atmosphere in a process known as atmospheric water harvesting.

What is Atmospheric Water Harvesting?

Atmospheric water harvesting is one of the methods that could save the Earth from running out of fresh water in the future. This new technology is mainly aimed at communities that live in regions lacking fresh water. It primarily operates on the existence of humidity. It involves the use of condensing tools that change the temperature of the humid air in the atmosphere. Once the humidity reaches this tool, there is a temperature drop to an extent that condenses the air, changing its state from a gas to a liquid. Then, the fresh water is collected in uncontaminated containers. When the process is done, the water is then used for several activities, such as drinking, watering crops, and cleaning.

The Use of Fog Nets

There are several ways to harvest water from the atmosphere. One of the most effective means known is the use of fog nets. This method is composed of net-like fog fences hung on poles in humid locations, pipes to transport the dripping water, and tanks to store fresh water. According to GaiaDiscovery, the size of the fog fences will vary, depending on “the lay of the land, space available, and the quantity of water needed.” 

Onita Basu, Associate Professor in Environmental Engineering at Carleton University, has recently been on a trip to Tanzania to test atmospheric water harvesting using fog nets. She explains that the fog nets depend on a temperature drop to change humidity into a liquid phase, and describes how the fog net operates to harvest and collect fresh water from moisture.

“When the humidity hits the fog net, because there is a surface, the water goes from the vapor phase to the liquid phase. As soon as it goes to the liquid phase, it just starts to drip down the fog net. There’s a catchment trough. The water drips down the fog net into the catchment trough, and then, from there, it goes to a bigger collection basin,” Basu says.

There need to be certain conditions for effective atmospheric water harvesting using fog nets. High wind speeds and an adequate temperature change are required to harvest enough water from the atmosphere. Basu emphasizes the importance of high humidity for the process when she says, “[Fog nets] can’t create water when there’s no water to start with.”

Another way to achieve the temperature drop is by pushing air above the ground to the underground, which has a colder environment that condenses the air quicker. 

The cleanliness of the collected fresh water is vital for a successful process. The sanitation of the water relies on whether the surface it hits is clean or not. The fog nets can be contaminated by human contact. 

“What you try and do to maintain the system to be clean as possible is just minimize any direct contact with hands, like human hands or whatever, from touching what is in the storage basin,” Basu advises.

Pros and Cons of Fog Nets

What makes fog nets very effective is that they don’t involve any moving parts. Other methods require metal surfaces and moving parts, which Basu believes is more expensive. It doesn’t mean, though, that fog nets are cheap. They also cover an adequate surface area to collect water.

However, fog nets do come with disadvantages. The biggest of these is that it can only work in places where there is humidity. Basu says that one of the areas she visited in Tanzania was an area that needed water, but the climate was very dry. Therefore, it might not be possible to use this method in areas that are too cold or too dry. Another flaw is that it is expensive because of its rare usage. Basu states that there are only two options to finance fog nets: “You either have to have a government that is looking actively for methods to help its people, and not all governments are doing that, or you have to have an NGO or some sort of other charitable organization that is willing to front that infrastructure cost.”

The Use of Atmospheric Water Generators

When manual methods to harvest water from the atmosphere cease to work, we must use more modern methods, such as the Atmospheric Water Generator (AWG). Unlike fog nets, the AWG uses electricity to complete these tasks. The generator is composed of a coolant system to cause a temperature drop in the air, as well as a purification system to sanitize the water. In an open environment, the electric energy can be obtained from natural energy sources, such as sunlight, wind, and waves. 

Simply put, the AWG operates as an air dehumidifier, except that it produces drinkable water. When humidity enters the generator, the coolant system condenses the air “by cooling the air below its dew point, exposing the air to desiccants, or pressurizing the air,” as specified by GaiaDiscovery. When the humidity reaches a liquid state, it goes through a purification process applied by an anti-bacteria air filter. The filter removes the bacteria, chemicals, and pollution from the water, resulting in crystal-clear water ready to be consumed by the people who need it.

Pros and Cons of Atmospheric Water Generators

The AWG is a very effective technology to harvest water from the atmosphere, since all it needs are air and electricity, which can both be obtained from natural energy sources. When equipped with a purification system, the water produced from the generator would be cleaner than water produced by most atmospheric water harvesting methods. Even though an AWG requires humidity to produce fresh water, it can be placed anywhere. Its portability makes it accessible in many emergency locations, such as hospitals, police stations, or even shelter for survivors of a damaging storm. It is valuable to areas that don’t support life due to lack of water. Unfortunately, AWGs are known to be more expensive than other basic atmospheric water harvesting technologies.