‘Cloud-milking’: the zero-energy technique keeping young trees alive | Environment

They call it cloud milking, a zero-energy technique to extract water from fog that is revolutionising the recovery of forests devastated by fire and drought.

The idea began as a pilot project in the Canary Islands. The plan was to exploit the moisture-laden “sea of clouds” that hangs over the region in order to aid reforestation, and has since been extended to several other countries to produce drinking water, and to irrigate crops.

“In recent year the Canaries have undergone a severe process of desertification and we’ve lost a lot of forest through agriculture. And then in 2007 and 2009, as a result of climate change, there were major fires in forested areas that are normally wet,” said Gustavo Viera, the technical director of the publicly-funded project in the Canaries.

Viera said that after the devastating fires they sought ways to deliver water to remote, mountainous areas without creating infrastructure, or using fossil fuels to extract ground water from deep wells.

The project, named Life Nieblas (niebla is the Spanish word for fog) began, backed by the EU, intended to mimic the way that the leaves of the local species of laurel trees capture water droplets from fog, by using sheets of plastic mesh erected in the path of the wind. As the wind blows fog through the mesh, water droplets collect and fall into the containers below, which is used to irrigate new saplings until they have sufficient leaves to capture the water themselves.

However, the wind, though vital to the original structure, proved a problem as it destroys all but the smallest structures.

“We needed to solve the problem of the fragility of the netting while minimising the environmental impact,” Viera said. “We developed a system that imitates pine needles, which are very good for capturing water while also letting the air pass through, and it’s a system that can easily be replicated in other locations and that’s also easy to transport to where it’s needed.”

In the new models, water condenses on the fine metal fronds of the structures, replicating the way conifers collect water from the atmosphere.

The water is discharged automatically without any energy supply or CO₂ emissions and no machinery is used to transport it from one place to another. No electrical systems are used for irrigation and the water footprint is also reduced as no aquifers or rivers are exploited. The only power needed is for building the collectors and getting 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 are using individual water collectors of the type used to keep herbivores from eating young plants,” said Vicenç Carabassa, the project’s head scientist, who works for the Centre for Ecological Research and Forestry Applications (CREAF), a public research institute at the Autonomous University of Barcelona.

“They collect rain and the heavy dew that falls on summer mornings and also provide shade.”

Carabassa pointed out that not every type of fog is suitable because some don’t have a high enough moisture content. The ideal fog is orographic or mountain fog, which exists in many Mediterranean regions and also in northern Portugal.

“The Canaries are the perfect laboratory to develop these techniques,” said Carabassa. “But there are other areas where the conditions are optimal and where there is a tradition of water capture from fog, such as Chile and Morocco.”

The method is now being used to supply drinking water and water for irrigation to the Chilean coastal village of Chungungo in Coquimbo province, while in the Cape Verde archipelago Life Nieblas collectors, combined with locally-made wooden structures, are providing 1,000 litres of water per day, which is used to irrigate crops and water livestock.

All the information necessary to create fog collectors is freely available to the public on the project’s website, and Viera said they’ve had many enquiries.

The benefits are palpable. In the Barranco del Andén ravine in Gran Canaria, 35.8 hectares (96 acres) have been reforested and 15,000 trees of various laurel species have been planted, with a survival rate of 86%, double the figure of traditional reforestation.

“We have recovered the forest’s potential to capture atmospheric carbon and estimate that we have captured around 175 tonnes of CO₂ per year,” Viera said.

The Life Nieblas project saves not only in fossil energy consumption and CO₂, but it is also cheaper and uses less water than traditional reforestation systems.

“We’re living with drought throughout the Mediterranean and also in the Canaries and now every drop of water counts,” said Carabassa, adding that we have to learn to live with much less water.

“This technique is never going to be an alternative to a desalination plant but in remote areas where water supply is difficult and expensive this can be a real alternative.”