Feed Protein Innovation

Dairy processing waste to protein rich duckweed

By Jane Byrne

- Last updated on GMT

© GettyImages/Lenorlux
© GettyImages/Lenorlux

Related tags Dairy

Scientists in Ireland are working on a process to produce duckweed for use in animal feed by capturing essential nutrients in wastewater from dairy processing plants.

The team, based at University College Cork (UCC), said one of the objectives of their project, Newtrients, is to reduce Ireland’s reliance on soy imports for feed protein.

We caught up with UCC plant scientist and project lead, Professor Marcel Jansen, to hear more.

“This is actually quite a new project, it is being run over the next four years. It is funded by the Irish Environmental Protection Agency (EPA), which has a massive interest in the circular economy. 

"The trigger was the end of the milk quota and the local dairy industry beefing up production."

Ireland, one of the world’s biggest dairy product exporters, has increased milk production sharply since the abolishment of milk quotas in 2015.

This hike in the volume of milk being processed, along with stringent measures on emissions from the industry and increased need for operational efficiencies, is behind multiple technological and operational innovations underway within the sector.

Lots of milk but what to do with all that waste…

“Official policy documents talk about doubling of dairy production in a sustainable manner, and that is where the trouble starts - if you look at the processing of milk, you are talking about two to three liters of wastewater for every single of liter of milk that is processed.

“And treatment of wastewater for the dairy industry is a massive burden, in terms of costs. So, that is where our project fits it.”

The Newtrients team comprises engineering, microbiology and plant science experts.

“There are several departments within UCC involved because one of the things in the circular economy idea is that you need to bring several disciplines together.”

He said dairy industry wastewater is particularly attractive as potential source of valuable resources in Ireland as it is not contaminated with pathogenic material or heavy metals, which makes it possible to use recovered resources to grow protein rich plants. “Our starting point is milk which is food grade.”

The first strand of the initiative is treatment of the wastewater by acidogenic fermentation to produce bioplastics. That takes out the fatty acids from the dairy sector processing waste. “That process is very much coupled to the duckweed production strand; it will remove a lot of the organic matter, and that is good because plants cannot take up such components as lipids, sugars, proteins etc.”

The bioplastic production phase will not be detrimental, though, to nitrogen or phosphate levels in the wastewater, leaving the liquid with the ideal nutrient composition for growing Lemna or duckweed as a protein alternative to soy.

Duckweed is pretty comparable to soy in terms of its amino acid profile.”

Lemna is a very good species to work with; it adapts well to a wide range of conditions and is easy to grow, said Jansen.

He said the plant also grows quickly. “In our lab, we double the entire biomass in 36 hours.”

It is about closing the loop.

“The Irish dairy industry is doing all right at the moment in terms of milk prices but, in most years, the key factor determining whether the dairy farmer makes a profit or loss depends very simply on one thing – how much soy farmers need to buy in the winter. Any replacement of soy with a local source that might be cheap is going to increase the profitability of the sector.”

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The face to face event, our first, will look at novel approaches involving both traditional and alternative protein sources, focusing on routes to market success and how best to tackle the inherent challenges along the way: ensuring food safety, minimizing production costs, maximizing nutritional qualities, navigating the regulatory environment and securing consumer acceptance.

Next steps

The UCC team is currently looking at dairy processing waste and seeing whether they need to modify it, looking at what extent they would need to add nutrients so the duckweed plants would grow efficiently.

“We are working now in the lab with relatively small containers. In the next year, we will start to work on tanks of about 200 to 250 liters in volume, and when it comes to the third year, we should be working with systems in the range of 1,000 liters. Based on the literature, we expect to achieve 20 tons of dry matter per hectare in terms of duckweed productivity.”

This waste management approach might well be a solution for Ireland, but not necessarily for all markets, especially countries with high-density agriculture sector like the Netherlands, stressed Jansen.

“We need to view this project in context – we see in Ireland that may farms have poor patches or boggy soil where small wetlands can easily be created, utilizing land that does not have economical value.”

The short-term ambition is to drive a local circular economy - closing the nutrient cycle – whereby individual farmers would have a hectare of ponds, growing their own duckweed.

“If you look at farms supplying milk to local dairy processors, there are tankers going up full and coming back empty, so there is no reason why that wastewater can't be brought back to the farm.”

However, he said it could be a much bigger concept.

“I don’t see why people wouldn’t grow duckweed at much larger scale – at tens of hectares – specifically to create a cash crop for protein isolation.”

The researchers are mindful that yoghurt or cheese production creates a different type of processing waste and that the composition of milk varies across the season as well.

“So you need a system that is robust enough to deal with different waste streams.”

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