A PhD project in Sweden shows that animal manure and food waste can be transformed into raw materials for animal feed. Researcher Clarisse Uwineza at the University of Borås describes how organic waste streams are first converted into volatile fatty acids and then serve as food for an edible fungus that forms a protein-rich biomass. This brings a local substitute for soy and fishmeal closer, giving manure a valuable second life.
From waste to nutritious biomass
The route begins with anaerobic digestion. In an oxygen-free environment, microorganisms break down manure and food waste into short-chain fatty acids. These acids, combined with nitrogen and minerals from the effluent, form a stable breeding ground for growth. This transforms a drainage problem into a resource flow that can be controlled. The research group has chosen Aspergillus oryzae, an edible filamentous fungus also known from food processes such as miso and sake, which grows rapidly on these fatty acids. The fungal biomass contains a lot of protein, plus minerals and dietary fiber, and, according to the university, is easily digestible for animals.
Cultivation requires precision. Certain fatty acids can inhibit growth at high concentrations. Uwineza demonstrates that controlled dosing helps. By providing the acids in controlled doses, the fungus continues to grow gradually and yields increase, while maintaining its composition. This increases the robustness of the process and makes the transition from lab to practice more realistic. The setup accommodates both batch and fed-batch methods, where the supply of acids and nutrients follows the growth rate of the fungus and fluctuations in the digester effluent are absorbed.
Consequences for the chain and the climate
The university links the results to the circular bioeconomy. By utilizing local residual flows, the pressure on primary crops decreases and the dependence on imported proteins diminishes. This impacts the climate and land-use footprint of the ration. Along the lines outlined by Borås, the approach aligns with several UN goals, including Responsible Consumption and Production and Climate Action. Besides application as feed, the university also sees opportunities for materials based on fungal cells, such as leather-like applications or biobased plastics, allowing a single process to deliver multiple value streams.
For livestock farmers, digester operators, and feed companies, the focus is primarily on quality and continuity. Consider a stable effluent supply, a usable mix of fatty acids, attention to pH and ammonium, and a cultivation process that can operate continuously. Standardization and safety assurance are essential for integrating biomass into existing feed chains. The research offers concrete starting points for pilot projects alongside digesters, with clear roles for each link and prospects for scaling up if the composition and performance remain consistent.
Source: University of Borås
