Water is the nectar of life. All organisms on our planet owe their existence in some form or the other to this essential element, and we would not have had food on our tables if not for ‘usable’ water.
Most of the Earth’s surface is covered by water. According to the United States Geological Survey, “About 71% of the Earth’s surface is water-covered, and the oceans hold about 96.5% of all Earth’s water.” But ocean water is composed of a lot of salt -- as much as 35 parts per thousand in concentration. This intense salinity has made seawater all the less potable, unless there is significant investment towards desalination technologies. A classic case of, “Water water everywhere and not a drop to drink!”
The increasing birth rate, leading to overproduction and consumption, in tandem with the climate crises, culminating in drastic weather changes, including erratic rainfall, are negatively impacting the world’s freshwater tables, and thus agriculture -- a vicious cycle. By 2025, two-thirds of the world’s population may face water shortages. Freshwater, which we drink, bathe in, and irrigate farms, is incredibly rare.
“Only 3% of the world’s water is freshwater, and two-thirds of that is tucked away in frozen glaciers or otherwise unavailable for our use. As a result, some 1.1 billion people worldwide lack access to water, and a total of 2.7 billion find water scarce for at least one month of the year,” says The World Wide Fund for Nature. Less usable water translates to inadequate sanitation, exposing the vulnerable to disease. Hence, the ocean is viewed as the apt arena where a challenge can be turned into an opportunity, and scientists at the University of South Australia (UniSA) are trying to achieve that by experimenting and innovating with floating sea farms, as they try to solve the world’s hunger and thirst problems.
The world is going renewable, and the sun and the sea are where the solutions for tomorrow rest. UniSA researchers have ideated a unique project, through which they have created vertical sea farms floating on the ocean that can produce fresh water for drinking and farming. This first-of-its-kind self-sustaining solar-driven system evaporates seawater and recycles it into freshwater, growing crops without human intervention, and could address future global food and freshwater shortages, especially with the world’s population expected to balloon to 10 billion by 2050.
The vertical floating sea farm -- the brainchild of Prof Haolan Xu and Dr Gary Owens of UniSA’s Future Industries Institute -- comprises two chambers: an upper layer like a glasshouse and a lower water harvest chamber.
“The system works much like a wicking bed that household gardeners might be familiar with,” says Dr Owen, as quoted by the University of South Australia website. “However, in this case, clean water is supplied by an array of solar evaporators that soak up the seawater, trap the salts in the evaporator body and, under the sun’s rays, release clean water vapour into the air which is then condensed on water belts and transferred to the upper plant growth chamber,” he adds.In a field test, the researchers were able to, with an 80% survival rate, grow three vegetables – broccoli, lettuce, and bok choy – on seawater surfaces sans maintenance or additional clean water irrigation. The system, which is powered by solar light, is advantageous over other solar sea farm designs currently in trial, explains Prof Xu.
“Other designs have installed evaporators inside the growth chamber, which takes up valuable space that could otherwise be used for plant growth. Also, these systems are prone to overheating and crop death,” he says, as quoted by the UniSA website.
Low-cost and sustainable
Floating farms, with traditional photovoltaic panels harvesting electricity to power conventional desalination units, have also been proposed, but these are energy-intensive and expensive.
“In our design, the vertical distribution of evaporator and growth chambers decreases the device’s overall footprint, maximising the area for food production. It is fully automated, low cost, and extremely easy to operate, using only solar energy and seawater to produce clean water and grow crops,” the professor adds.
Meanwhile, Dr Owens says their design is only proof-of-concept at this stage, but the next step is to scale up, using a small array of individual devices to increase plant production. Addressing larger food supply needs will mean increasing both the size and number of devices. “It is not inconceivable that sometime in the future, you might see huge farm biodomes floating on the ocean, or multiple smaller devices deployed over a large sea area,” says Dr Owen.
Water, energy, and food security are the three most critical elements for achieving the 2030 UN’s Sustainable Development Goals. With sustainability as a core principle, the researchers’ prototype may be modified to produce greater biomass output, including using low-cost substrate materials like waste rice straw fibre, to make the device economically-viable. Through this path-breaking method, the researchers have highlighted that the recycled water thus produced is pure enough to be consumed, with salinity than the World Health Guidelines for drinking water (The pH level of the water sources should be between 6.5 and 8.5 on a scale ranging from 0 to 14. The best pH for drinking water sits at 7 - right in the middle).
Source: The University of South Australia