Circular Farming

Rebecca Pool explains how circular farming and food production innovation are set to cost-effectively feed the world without damaging the planet.

Recent figures from Climate Watch indicate that agriculture is the second-largest contributor to global greenhouse gas emissions after energy and transport, producing 12.16% of all emissions.

At the same time, the United Nations Food and Agriculture Organisation reports nearly half of our habitable land is used for agriculture while the World Bank states food systems are the leading source of biodiversity loss and use around 70% of fresh water.

Factor in how excessive use of chemical fertilisers can degrade soils, yet food demand is set to rise as the global population swells to nearly 10 billion people by 2050. How can we feed the world without damaging the environment? One answer is to instil circularity in agriculture.

What is circular farming?

Circular farming biorefinery — Making more of grass: the green biorefinery demo-site in Denmark [GO-GRASS].

Circular farming is a way to farm sustainability while adopting the latest scientific innovations. Mixed crops, organic farming, aquaculture, water recycling and wastewater re-use can all help to ensure waste from one part of the process becomes a resource for another.

Together, these innovations can close the loop on farming processes. However, while the concept isn’t new, a rising number of innovative projects indicate it is here to stay. One case in point is “GO-GRASS”, set up in 2019 to unlock the potential of the European Union’s grassland.

These areas occupy around 17% of the region and are largely left unused, so as part of this project Morten Ambye-Jensen, Head of the Centre for Circular Bioeconomy at the University of Aarhus, has been managing a green biorefinery demo-site in Denmark to find out how to cost-effectively process freshly harvested grass.

“We’ve wanted to use green biorefining to reduce the environmental impact of Danish agriculture, currently dominated by annual cereals and corn,” he said.

Morten Ambye-Jensen, Head of the Centre for Circular Bioeconomy and GO-GRASS lead, outside the green biorefinery demo-site in Denmark. [Lars Kruse AU 2020]

“Grasses are one solution as they can reduce nitrate leaching, increase soil carbon and eliminate the need for pesticides. But farmers need a business case to grow perennial grasses – we believe green biorefinery is the technology tool that could make that.”

The demo-site has been macerating and pressing the grass to produce protein concentrate to feed to pigs and poultry, a greener alternative to importing soy for livestock fodder.

A fibrous pulp and brown juice are also produced from the process. The pulp can be fed to grazing animals and the juice, with its soluble sugars and nutrients, can be used for biogas production.

Ambye-Jensen says that he and GO-GRASS colleagues, plus other green biorefineries and commercial players around Denmark, have been optimising processes. Their results continuously indicate that protein concentrate quality is at least good enough to substitute soy.

“This is happening – the green biorefinery industry is rolling out,” highlights Ambye-Jensen.

“We now have the Danish government offering subsidies to build commercial green biorefineries, and I’m absolutely sure there will be more efficiency improvements when more commercial stakeholders join us to optimise logistics and large-scale processing.”

From agriculture to aquaculture

Microalgae: Growing these organisms can help to close the loop in farming processes. [Necton].

Taking a different tack, another project called “REALM” is developing cost-effective methods to grow microalgae in circular production.

These single-celled micro-organisms can provide a highly nutritious alternative to fish-feed and have already been exploited for human food, cosmetics, plant bio-stimulants and energy applications – but, like green biorefinery, costs can be high.

REALM has proposed growing freshwater microalgae in agricultural wastewater, specifically fertiliser-filled drain water from greenhouses which offers just the right nutrients for growth.

Microalgae — A pilot raceway pond, in which microalgae grows, for experimental tests at Necton. [Necton]

As part of a circular system, the drain water can be transferred to either raceway ponds or photobioreactors in which the microalgae grow, cleaning the wastewater of nitrates and phosphates.

Once fertiliser concentration is sufficiently reduced, the water can then be released back to the environment or transferred back to the greenhouse.

Solar energy will power the circular set-up, including carbon dioxide capture technology needed for microalgae growth. Once harvested, the microalgae “biomass” can be transported to a processing facility and transformed into bio-products for both agriculture and aquaculture.

“This is a totally new concept – we’ve got decentralised microalgae production next to the greenhouses,” points out Mariana Carneiro, Innovation Manager at Portugal-based microalgae producer and REALM coordinator, Necton.

“It benefits the farmers as they have a profitable solution for contaminated water as they can sell microalgae to, say, Necton, or any other company that will refine this into products.”

Like GO-GRASS, results are promising. Facilities already set up in Finland and The Netherlands, and under development in Portugal and Spain, are testing different freshwater algae species, and reducing contamination levels in the drain water.

A specially developed online monitoring and control system is also set to further refine production and prevent nutrient waste.

As Carneiro says: “If anyone wants to grow microalgae in, say, Lithuania or France or even outside of Europe, they can look at the different cultivation set-ups we have and choose which will be more effective.”

Carneiro is confident that in the next couple of years, micro-algae production will be cheaper and run more efficiently.

Mariana Carneiro is Innovation Manager at Necton and coordinator at REALM. [Necton]

“The public wants more sustainable products, and microalgae can contribute to this,” she says. “Traditional agriculture took millennia to establish… but I see many other projects doing great work – we’re now moving a lot faster.”

Kris Heirbaut, a Flemish farmer driving circular farming forward with his 65 hectares of cultivated land and cow herd, would agree.

Heading up Heirbaut ALgriculture, Heirbaut joined forces with researchers from “Grass2Algae”, funded by the Flemish Department of Agricultural and Fisheries, to economically cultivate algae.

In the project, waste grass was pressed to separate the juice from the fibres – the juice was then used to grow microalgae whilst the fibres were used in anaerobic digestion or sold as a feedstock for biomaterials.

Heirbaut is using research from Grass2Algae to create circularity on his farm. Manure from his cows feeds his small anaerobic digester, with the resulting biogas fulfilling around 65% of the farm’s energy needs, including milk pasteurisation and freezing in their dairy.

“We can load a battery with electricity generated from this process – this can also power our farm,” says Heirbaut.

On top of this, the carbon dioxide from biogas production is filtered through his microalgae bioreactor and broken down.

The carbon feeds these micro-organisms as they grow in the grass juice squeezed from excess cuttings, and the oxygen escapes in a degassing vessel.

Heirbaut has been working with the freshwater algae, chlorella, and as he highlights: “Pressing juice from grass is ideal to safely cultivate chlorella… and I do not want to use mineral fertiliser.”

Building a supply chain

Circular farming grass — Lucerne grass, also known as Alfafa, at different stages of processing. [GO-GRASS]

According to Heirbaut, his farm generates “a lot of chlorella powder”, so he and colleagues have been working hard to create demand for this.

They initially used chlorella in their own food, sold in their farm shop, and then started to partner with small food producers. Heirbaut is now hoping to join forces with larger retailers but believes this could take time.

“We’ve proven [our] consumers like algae… and circular farming on arable land should be accepted as the way to go,” he says

“Everywhere I go, I’m told that it’s great to see that people like myself realising it’s time for change,” he adds. “So give us time, this is new. [Circular farming] needs development and innovation, but excellence will follow.”

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