What are underwater farms? And how do they work?

Could underwater strawberries and deep-sea herbs provide a more sustainable alternative to land-based farming?

Industrial agriculture is struggling to meet the needs of a rapidly growing population. And decades of intensive farming has taken a heavy toll on the environment.

An over-reliance on pesticides, displacement of wildlife, the wasting of gallons of water and the generation of harmful emissions are damaging our world.

So, scientists and entrepreneurs are hoping underwater farming could address these issues by growing crops under the ocean, eliminating the need for pesticides, while also reducing water use and carbon emissions.

Indeed, the UN estimates the world could easily be fed if we used just 2% of the oceans for sustainable farming.

Boosting sustainability with underwater crops

Aquaculture has long been used to grow and harvest foodstuffs such as seafood, but several companies are now looking at ways of farming traditional crops such as strawberries and herbs under the sea.

Nemo’s Garden is an underwater farming project consisting of six air-filled plastic pods, or biospheres, anchored at the bottom of the sea off the coast of Noli, Italy.

The plastic pods are suspended at different depths – from between 4.5 to 11 metres – below the water’s surface, and each is equipped with sensors to measure carbon dioxide and oxygen levels; humidity, air temperature and illumination.

Created by diving company Ocean Reef Group in 2012, the project has already yielded everything from tomatoes, to courgettes, beans, mushrooms, lettuce, orchids and aloe vera plants using hydroponic techniques.

This means that plants are grown, without soil, in a nutrient-rich solution to deliver water and minerals to their roots, in a controlled environment.

Underwater farming means no pesticides are needed

Each dome is equipped with seedbeds and a 10-metre spiral tube. Irrigation water and fertilizer are kept in a tank at the lowest part of the spiral, and are delivered to the plants using a pump.

All these functions can be controlled from an above-water control tower, which is also fitted with solar panels that control a fan in each biosphere to reduce humidity on the plants.

Growing crops underwater also benefits the environment by eliminating the need for pesticides as no pests can enter the pods unless they are introduced.

In addition, the biospheres conserve water; seawater in the pods evaporates and then condenses back down to provide the plants with fresh water.

An external water source is only required when initially growing the plants.

Vertical underwater farming of kelp and shellfish

Meanwhile, a North America-based nonprofit organization called GreenWave has developed a sustainable agricultural technique called vertical underwater farming or regenerative ocean farming.

The company grows a range of seaweed types like kelp and shellfish, including mussels and scallops, on a rope scaffolding system under the sea.

The model benefits the local environment by requiring zero inputs such as water, fertilizer or feed, while also rebuilding marine ecosystems.

At the same time, seaweed absorbs CO2 from the ocean, making the water less acidic and helping wildlife thrive, while bivalves such as oysters actually improve water quality.

GreenWave’s polyculture farming system also promises high yields with a small carbon footprint, and a low barrier to entry as anyone with 20 acres, a boat and $20,000 to $25,000 can start their own farm.

A sustainable seaweed solution

In Namibia, Kelp Blue has been granted environmental clearance to start the underwater farming of seaweed crops that can be harvested for fertilizers, textiles and pharmaceuticals off the country’s coast.

Kelp is one of the fastest-growing organisms on the planet. It helps create habitats for many marine species and can be sustainably and repeatedly harvested for at least seven years.

The seaweed is also a very efficient carbon sink, with the company aiming to capture millions of tonnes of CO2 a year by 2050.

Also focusing on seaweed is Bangalore-based Sea6 Energy, which has designed a tractor-like vehicle called a ‘SeaCombine’ to seed and harvest tropical underwater plants.

The fully mechanized seeding and harvesting catamaran is currently being used for seaweed farming off the coast of both India and Indonesia.

As well as providing a gelling agent for use in food production, Sea6 Energy’s produce can be used as biofuel, in bioplastics and in agriculture, among other things.