Aquaponics: how gases help advance sustainable food production

Aquaponics is a form of sustainable agriculture that combines raising fish in tanks (recirculating aquaculture) with soilless plant culture (hydroponics). In aquaponics, the nutrient-rich water from raising fish provides a natural fertilizer for the plants and the plants help to purify the water for the fish. Literally speaking, Aquaponics is putting fish to work.

One of the pioneers in this business, is a company in northern Sweden. "Our vision is to have locally produced fish and vegetables in every grocery store, no matter where they are located," says Daniel Brannström, one of the founders of Peckas Naturodlingar. That vision has its roots in the environmental awareness of Pecka Nygård, a fisherman and entrepreneur from northern Sweden who is also the company’s namesake and one of its founders.

Back in 1996, Nygård began experimenting with land-based fish farming methods out of growing concern for traditional fish farming’s impact on the Baltic Sea. He built a small fishpond and greenhouse in his backyard in Härnösand, a coastal town of around 20,000 residents that started off as a fishing village in the 1600s. From there, he started growing tomatoes and raising rainbow trout in the rudimentary construction.

For the next two decades, the fisherman-farmer continued to tinker with the method, known as aquaponics. It combines aquaculture - fish farming - with hydroponics, the growing of plants in a water-soaked bed of gravel rather than soil.

‘Closed-circuit farming’

Nygård even coined his own Swedish word for the process - kretsloppsodling, a combination of kretslopp (closed circuit) and odling (farming) to better encapsulate the circular nature of the approach. " Kretsloppsodling builds a symbiotic relationship between the fish and the plants. No water is lost except for what the plants use to grow. It’s really a closed system that produces no emissions," explains Brannström.

As word spread about Nygård’s “closed-circuit farming” and demand for more sustainable forms of agriculture continued to grow, the ad hoc research project evolved into Peckas Naturodlingar, which was established in 2015.

Today, the company – commonly known as Peckas – operates greenhouses totalling more than 13,000 square metres as well as fifteen 40-square-metre fish tanks on the outskirts of Härnösand. The size of the operation has led Peckas to claiming to be the first company in the world to demonstrate the viability of industrial scale aquaponics.

"We’ve now shown that aquaponics can work on a large scale. And our goal is to deliver turn-key solutions to customers, mostly grocery stores, interested in starting their own growing operations," says Brannström.

Peckas’ tanks are filled with water and newly hatched fish that are fed a steady diet of protein-rich fish food. The waste produced by the fish is then carried away from the fish tanks and into one of Peckas’ massive 4,000 square-metre greenhouses. The greenhouses feature four-metre-high growth towers, helping to maximize the use of space by growing vertically. Plants are anchored in specially designed beds of gravel, facilitating the flow of the nutrient-rich water over the plants’ roots after it's been pumped from the fish tanks.

CO2: an important ingredient

Bacteria in the plant beds help convert the ammonia from the fish waste into nutrients for the plants. This process filters out the fish waste, resulting in clean water which is then pumped back into the fish tanks. This is one of the coolest things about Aquaponics, that it mimics a natural ecosystem. Aquaponics represents the relationship between water, aquatic life, bacteria, nutrient dynamics, and plants which grow together in waterways all over the world.

"It’s like our tomato plants serve the same function as a filter in a home aquarium," Brannström explains. "And in the time it takes a fish to grow to about one kilogramme, you can produce about 10 kilos of tomatoes."

With recently added capacity, Peckas facilities can produce up to 400 tonnes of vegetables and 40 tonnes of fish annually. Gas is also a critical component of Peckas’ aquaponics solution. While the fish produce carbon dioxide naturally, levels aren’t high enough to optimize plant growth. Thus, CO₂ supplied by Linde is pumped into the greenhouses, doubling levels from around 450 ppm to between 800 and 1,000 ppm.

"Carbon dioxide is an extremely important ingredient for the whole process," explains Brannström. "It creates ideal conditions for growing tomatoes and other plants. You end up with substantially higher yields." Greenhouses are also a practical way to take CO₂ out of the atmosphere instead of burying excess carbon dioxide underground. "It’s better to build more greenhouses and let plants consume CO₂," he says.

Local production, lower emissions

Aquaponics also uses water much more efficiently than traditional agriculture as the same water can be cycled through the tanks and greenhouses. And the resulting food products are also free of hormones, pesticides, and antibiotics. A plant can be set up anywhere, close to the consumers, providing fresh local food. Furthermore, no harmful emissions are released in the production process, and there is great potential to cut down on transport emissions as more food can be produced locally.

"The pandemic has shown the importance of increasing the amount of locally produced food," says Brannström. Looking ahead, Brannström is bullish about Peckas’ potential to help spawn a revolution in sustainable, locally produced food that can support a broader shift toward more sustainable food production. "Aquaponics is the future of farming," he says.

Text: Carina Aspenberg