In future, we will eat protein produced from wastewater

Environment and sustainability 12. jul 2022 2 min Associate Professor Yifeng Zhang Written by Kristian Sjøgren

Researchers have developed a method of extracting nitrogen from wastewater and getting bacteria to use the nitrogen to produce protein that can be used as food for people. The researchers recently started a project to build the first large-scale pilot plant.

The world is facing an ever-growing food crisis that is difficult to solve sustainably with everyone having enough food without ruining the planet.

Bacteria, fungi and algae all have potential to create sustainable food, but so far the costs associated with producing food using microbes have outweighed the potential benefits.

New research now shows how bacteria can use sustainably extracted molecular building blocks from wastewater to produce some of the protein required to feed an ever-increasing world population.

The research has been published in Chemical Engineering Journal.

“We know that protein is crucial to solve the food crisis, but technology needs to become better and cheaper before protein can help to solve the global food crisis. Sustainability and cost–effectiveness are not necessarily synonymous, which is why our research group is exploring opportunities to make microbial production of protein both sustainable and inexpensive,” explains a researcher behind the study, Yifeng Zhang, Associate Professor, Department of Environmental Engineering, Technical University of Denmark, Kongens Lyngby.

Bacteria produce protein from wastewater

Wastewater contains a lot of nitrogen that bacteria can use to make protein.

An obvious problem, however, is whether protein made directly from and in wastewater is palatable, and the nitrogen in wastewater must therefore be extracted and then fed to the bacteria. The researchers have succeeded in doing this.

“We have developed a method for recovering pure nitrogen from wastewater. Wastewater is a sustainable source because it is plentiful on a daily basis,” says Yifeng Zhang.

Extracting pure nitrogen from wastewater

Extracting nitrogen from wastewater uses electricity, but if this comes from renewable energy sources, such as wind energy, converting wastewater into nitrogen can be made sustainable.

The technology involves a cation exchange membrane and a two-chamber electrochemical recovery cell.

The membrane is between the two chambers, one containing pure water and the other containing wastewater. Applying electric current to one side of the cell draws nitrogen from the wastewater into the chamber with pure water.

From there it bubbles out and turns into ammonium gas.

The researchers can also extract oxygen and hydrogen from the cell, which together with carbon dioxide are the other components bacteria need to produce protein.

“We can therefore obtain everything the bacteria need from one system and sustainably by using renewable electricity. This is similar to power-to-X, except that we are storing energy as protein,” explains Yifeng Zhang.

Constructing a larger production plant

In connection with the system for harvesting the necessary components, the researchers also built a fermentation unit in which the bacteria can multiply and produce protein.

So far, the researchers have shown that the necessary components can be sustainably harvested n the quantities needed from wastewater and the bacteria can produce the required protein.

The next step is to scale up production so that it becomes commercially attractive.

This part of the research began in early 2022, when the researchers embarked on a major international project for building the first large-scale plant for producing protein with components taken directly from wastewater.

“The project is set to last for 5 years, so by that time we will be able to show not only that bacteria can be used to produce food-quality proteins from wastewater but also that this can be done on a large and economically attractive scale,” concludes Yifeng Zhang.

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