Sustainable agriculture: how the future feeds the world

Some years ago, Australian entrepreneurs started cultivating 20 acres of sand – and now, 15% of Australia’s tomato produce is grown in this flourishing desert by an agricultural firm called Sundrop Farms.

This Australian project grows vegetables fully powered by renewable energy and water sources: sunlight and seawater. The combination of a flat piece of land, money, sun, knowledge and a coastal location can make the impossible possible – a greenhouse oasis in the desert.

Van der Hoeven Horticultural projects, a Dutch firm with lots of experience in the international agriculture market, engineered this enormous seawater greenhouse project.

So, a global challenge is getting a response: this self-sustaining type of farming contributes to our global food problem. The world population will grow to 9.6 billion people in 2050, if the UN forecasted right. The quantity of food production needs to parallel the growth in population, increasing by 70% over the next thirty-three years.

However, one factor that is exacerbating the complexity is climate change: farming conditions are getting more difficult and water is the protagonist.

Reliable water sources

“Water is always the obstacle in countries such as Australia,” Peter Spaans, Commercial Director of Van der Hoeven, explains. “Farmers always need to settle near a freshwater source; for example, a sewage system whose water could be cleaned for horticulture.

However, during times of drought, the amount of water which can be used for agriculture is limited, which can entirely ruin crops or at least compromise the quality of the products.”

Scientists find it hard to predict trends in weather conditions given the uncertainties of climate change, but many see heavier rainfall – causing floods – and more frequent, extreme droughts as a consequence of our changing climate.

Farmers will need to be independent of weather conditions. Whether there are droughts or floods, farming must continue.

A seawater greenhouse provides the perfect farming conditions – in a sustainable way. The greenhouse takes away the need for fertile soil, the sun functions as an infinite source of renewable energy, and the sea is an inexhaustible source of water.

The seawater greenhouse

The saltiness of seawater is the main challenge for a horticulture project like Sundrop Farms. While plants soak up freshwater, seawater has the counter effect, withdrawing water from leaves and stems. A technical solution was needed for freshwater.

In this case, a tower of 115 metres high, constructed on the sandy ground is the main player in both the desalination process and the energy production. The top of the tower, to which seawater is pumped, is the heart of the system. Solar rays, reflected by 23,000 surrounding mirrors, heat up the water to create steam. The steam is then converted into freshwater through condensation; into energy by a turbine; and into heat. To cool the greenhouses – when necessary – cold seawater can be used again.

Desalination techniques, as illustrated, are widely used, but its use in agriculture is relatively unconventional. Main reason? The high costs and energy demand.

Investment as key driver

“The technique of desalinating seawater could be applied everywhere, but is extremely expensive. If there is enough freshwater, there is no need to use seawater.” Dry and sunny climates can reach the highest efficiencies, given the amount of solar energy and the lack of drinking water.

Paying the energy and water bill 20 years upfront is how Spaans describes the investment made. And yes, it does pay off, but it takes a lot of time. The project in Australia is being done as a future investment, to develop the technique. “We see a lot of potential in the Middle East, where 80% of the freshwater supply is used for farming.”

Future-proof scenarios

In terms of the future of agriculture, Spaans sees a world in which most people live in cities which are surrounded by large horticultural projects. In that way, food is grown – relatively – locally. Urban farming is not an alternative for horticulture according to Spaans: rather, it is a social way of involving urban inhabitants in the process of growing crops, but it will not be able to supply the demand for food.

Seawater greenhouses are a way to supply cities in dry regions with a guaranteed amount and quality of food. One challenge of local farming on a large scale is a lack of knowledge: inhabitants of dry areas have little experience with horticulture.

Will this immense seawater greenhouse experiment be the start of a sustainable agricultural revolution? “We planned – wisely – to start small, with less than 20 acres,” laughs Peter Spaans, “however, the investor’s requirements pushed the project towards this immense size. It took time and effort, but now it is working very well.”

Information:

This article was written by Linda Vos. She has a Bachelor Degree in Architecture and is currently a Master student in Science Communication and in Building Technology. The article is derived from her interest in sustainability, and is also in preparation for an architecture project she is working on now – the design of a sustainable greenhouse in the Maldives. The shortage of freshwater there triggered her to dive into this subject even before the start of the project.

She explored the possibilities of ‘off-grid’ agriculture to write this feature article. To do an interview, she found an international horticulture firm located in the Westland that was willing to talk to her. Vos is now working to incorporate the ideas she got from her interviewee into her own project, though on a much smaller and more accessible scale for the target group in the Maldives.

• About fifteen Science Communication master students take the subject Science Journalism at TU Delft every year. One of their assignments is to write a feature article on their original field of expertise.

With grateful thanks to InterSECtion, the study association of the master study Science Education and Communication.

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