“Fog eating” describes fog harvesting, the practice of capturing water from atmospheric fog for human use. This low-technology approach provides a decentralized source of freshwater by utilizing microscopic water droplets suspended in the air. The technique is well-suited for arid coastal regions and mountainous areas where frequent fog, often called “advection fog,” occurs but where rainfall is minimal. This method offers a sustainable alternative to traditional water sources.
The Science Behind Fog Collection
Fog is essentially a cloud lying close to the ground, composed of water droplets typically ranging from 1 to 40 micrometers in diameter. To convert this airborne moisture, fog harvesting systems employ large, vertical mesh nets installed perpendicular to the prevailing wind direction. These nets are often constructed from materials like polypropylene or nylon, selected for their durability and physical properties that encourage droplet capture.
As the wind pushes the fog through the mesh, the tiny droplets collide with and adhere to the fibers of the material, a process known as impaction. Once attached, these microscopic drops coalesce to form increasingly larger droplets. Gravity then takes over as the drops become too heavy to remain suspended on the mesh surface.
The accumulated water runs down the fibers and drips into a gutter system located at the base of the net. Under optimal conditions, a single square meter of a well-designed fog net can yield between 2 and 10 liters of water per day. The efficiency of this passive collection method relies heavily on environmental factors, including the liquid water content of the fog, wind speed, and the specific material properties of the collector mesh.
Factors Affecting Water Potability
While fog collection is relatively clean compared to surface sources, the collected water is not automatically safe for drinking. Fog droplets form around airborne particles, known as condensation nuclei, which can include dust, soot, and particulate matter. Near urban centers or industrial activity, fog can also absorb airborne pollutants, including organic compounds and heavy metals, compromising its purity.
Therefore, post-harvest treatment is necessary to ensure the water is potable. This treatment typically involves a multi-stage process, beginning with basic filtration to remove larger debris. Further safety measures include disinfection methods, such as UV sterilization or chlorination, to eliminate microbial contaminants.
Researchers are also developing advanced collection materials that incorporate photocatalytic nanoparticles, such as titanium dioxide, directly into the mesh. When exposed to sunlight, these coatings can passively break down organic pollutants as the water is collected, simultaneously harvesting and purifying the water. This innovative approach addresses contamination challenges from air quality, particularly in areas where traditional treatment infrastructure is lacking.
Global Applications and Future Potential
Fog harvesting technology is currently implemented in numerous water-stressed regions, serving as a reliable, decentralized water resource. Prominent examples include the mountainous coastal deserts of Chile and Peru, where fog is a constant feature due to cold ocean currents meeting warm air. Projects in Morocco, such as the one in Boutmezguida, have successfully scaled the technology to supply thousands of liters of water daily to local communities.
The method requires no external energy input for collection and has a low operational cost, making it highly suitable for remote villages. Ongoing research focuses on improving collection efficiency through biomimicry, designing mesh structures that imitate the water-collecting abilities of desert plants and insects. Scientists are exploring advanced materials and specialized coatings to maximize the rate at which droplets are captured and drain.
The future potential lies in optimizing passive collection systems through structural improvements and the integration of novel materials like hydrophilic coatings, which encourage water to spread into a thin film that is easier to treat. By increasing efficiency and integrating purification directly into the collectors, fog harvesting offers a scalable strategy for climate-resilient water management worldwide.