Raising cattle, pigs, chickens, and other livestock requires feed. A lot of feed. In fact, almost half of our global agricultural area is used to grow feed such as soy, rapeseed, and grain, which is eaten by livestock.
In Denmark, the number is even higher—almost 80 per cent of the agricultural area is used for feed production. And this has a wide range of consequences: pollution from pesticides and fertilizers, CO2 emissions from agricultural machinery, and land that is taken from wild nature and therefore affects biodiversity. In countries such as South America and Asia, large forest areas are felled to use more land for feed production.
“It’s a huge problem. We simply have to reduce our animal food consumption, but unfortunately that’s not the way things are going. So it’s really important that we pursue an efficient and sustainable animal feed production,” says Tavs Nyord, Senior Consultant in Concito’s food programme.
At DTU, researchers are developing solutions that can help create more sustainable feed production in the future by using everything from methane to bread and algae. Read about the three projects here:
Food waste becomes animal feed
Leftovers from dinner, limp cucumbers, and mouldy rye bread can be given new life thanks to researchers from DTU who have developed a technology that utilizes by-products from food waste to produce protein-containing feed for livestock.
Currently, some food waste is used to produce heat and electricity by extracting, e.g., biogas from the waste, but the organic material can actually be used in a more optimal and valuable way according to Professor Irini Angelidaki from DTU Chemical Engineering who is heading the project PROFIT.
In the project, food waste from the citizens of the City of Copenhagen is converted into methane, while nutrients such as ammonium and phosphate are extracted thanks to a new electrochemical method developed at DTU.
The methane gas is fed into a bioreactor together with so-called methane-oxidizing bacteria that eat the methane and convert it into a single-cell protein. The proteins are freeze-dried and made into a reddish powder that consists of 70 percent protein with a number of important amino acids that can be added to animal feed and fed to pigs and cattle as an alternative to soybeans. In this way, virtually no food waste is wasted.
From the baker to the fishmonger
Every day, tonnes of bread and pastries are discarded because the stores can no longer sell it when it starts to go stale. According to the Food and Agriculture Organization of the United Nations (FAO), one third of all food is wasted, resulting in 3.3 million tonnes of CO2e emissions globally. But instead of the bread going into the trash, DTU researchers are working to convert it into proteins that can be used for fish feed.
Associate Professor Mohammadamin Mohammadifar from DTU Food and his colleagues collaborate with the company G2B BioSolutions, and they get stale bread and pastries from industrial bakeries in a number of supermarket chains such as Lidl and Salling Group. The bread is then fermented in a fermentation vat[S1], so the starch in the bread is converted into sugar, and when yeast is added, the sugar is converted into ethanol. The ethanol can be used as fuel, and during the process, protein is formed as a by-product. This protein contains 70 per cent crude protein as well as a number of essential amino acids, so almost everything in the bread is utilized.
The protein is tested as fish feed by the Danish company BioMar—one of the world’s leading fish feed manufacturers, but the protein can also be added to feed for other animals such as cattle, pigs, and chickens.
The project will end in January 2025, but DTU and G2B BioSolutions have already demonstrated industrial scale potential in 1,200-litre fermentation vats.
Algae utilize CO2 and are converted into fish feed
Shipping containers can do more than move goods across the world’s oceans. They can also be used to grow algae for the sustainable fish feed production.
Senior Researcher Ivar Lund and his colleagues from DTU Aqua have installed long pipes filled with salt water in containers, where they are illuminated by powerful LED lights and supplied with CO2 and nutrients. This causes microalgae to grow, which can be used for fish feed. Algae are high in protein and in unsaturated omega-3 fatty acids, both of which are good for fish.
If you use the technology for fish farming, the production becomes more circular, as fish farms discharge organic sludge that ends up as wastewater at a treatment plant. Here, the sludge is converted into biogas, and by cleaning the biogas of CO2, it can be reused in the algae production in the container pipes. When the fish have eaten the algae feed, they release new sludge, and the cycle can start over.
