They call it cloud milking, a zero-energy technique for extracting water from fog that is revolutionizing the recovery of forests devastated by fires and drought.
The idea was born as a pilot project in the Canary Islands. The plan was to exploit the moisture-laden “sea of clouds” hanging over the region to aid reforestation, and has since spread to several other countries to produce drinking water and irrigate crops.
“In recent years the Canary Islands have suffered a severe process of desertification and we have lost many forests due to agriculture. And then, in 2007 and 2009, as a consequence of climate change, large fires occurred in normally humid forest areas,” says Gustavo Viera, technical director of the publicly funded project in the Canary Islands.
Viera said that after the devastating fires they looked for ways to bring water to remote, mountainous areas without creating infrastructure or using fossil fuels to extract groundwater from deep wells.
The project, called Life Nieblas (fog is the Spanish word for fog) began, backed by the EU, with the intention of imitating the way the leaves of local laurel species capture water droplets from fog, by using sheets of plastic mesh erected in the path of the wind. As the wind blows mist through the mesh, water droplets collect and fall into containers below, which are used to water new saplings until they have enough leaves to capture water on their own.
However, the wind, although vital to the original structure, proved to be a problem as it destroys all but the smallest structures.
“We needed to solve the problem of network fragility while minimizing the environmental impact,” Viera said. “We developed a system that imitates pine needles, which are very good at capturing water and at the same time letting air through, and it is a system that can be easily replicated in other places and that is also easy to transport to where it is needed. ”.
In the new models, water condenses on the structures’ thin metal sheets, replicating the way conifers collect water from the atmosphere.
The water is poured automatically without any power supply or CO₂ emissions and no machinery is used to transport it from one place to another. Electrical systems are not used for irrigation and the water footprint is also reduced by not exploiting aquifers or rivers. The only energy needed is to build the collectors and place them in place.
A slightly different technique is also being applied to reforest an abandoned quarry in Garraf, a rugged area south of Barcelona.
“Here we use individual water collectors, the type used to prevent herbivores from eating young plants,” says Vicenç Carabassa, chief scientist of the project, who works at the Center for Ecological Research and Forest Applications (CREAF), an institute research public at the Autonomous University of Barcelona.
“They collect rain and the heavy dew that falls on summer mornings and also provide shade.”
Carabassa noted that not all types of fog are suitable because some do not have a high enough moisture content. The ideal fog is orographic or mountain fog, which exists in many regions of the Mediterranean and also in the north of Portugal.
“The Canary Islands are the perfect laboratory to develop these techniques,” said Carabassa. “But there are other areas where conditions are optimal and where there is a tradition of collecting water from fog, such as Chile and Morocco.”
This method is now used to supply drinking water and irrigation water to the Chilean coastal town of Chungungo, in the province of Coquimbo, while in the Cape Verde archipelago Life Nieblas collectors, combined with locally made wooden structures, provide 1,000 liters of water per day, which is used to irrigate crops and water livestock.
All of the information needed to create fog collectors is freely available to the public on the project website, and Viera said they have had many inquiries.
The benefits are palpable. In the Barranco del Andén, in Gran Canaria, 35.8 hectares have been reforested and 15,000 trees of various species of laurel forest have been planted, with a survival rate of 86%, double that of traditional reforestation.
“We have recovered the forest’s potential to capture atmospheric carbon and we estimate that we have captured around 175 tons of CO₂ per year,” said Viera.
The Life Nieblas project not only saves on fossil energy consumption and CO₂, but is also cheaper and uses less water than traditional reforestation systems.
“We live with drought throughout the Mediterranean and also in the Canary Islands and now every drop of water counts,” said Carabassa, adding that we have to learn to live with much less water.
“This technique will never be an alternative to a desalination plant, but in remote areas where water supply is difficult and expensive, it can be a real alternative.”