In the frame of the research project ‘BioProfit’ supported by the Austrian Cooperative Research (ACR), a process upgrading the digestate from biogas plants to valuable liquid fertilizer and humus is being developed. The solid phase of the digestate contains most of the plant-available nutrients and carbon, while the liquid phase contains particularly high amounts of nitrogen. Using a membrane distillation (MD) process, a high-quality liquid nitrogen fertilizer can be produced from the liquid fraction. This fertilizer can be deployed as a base fertilizer in agriculture, for example.
With regard to the development of the membrane distillation process an important milestone could be reached in November 2022: the test series using a container-scale MD pilot plant with large-scale membrane modules was successfully started. The aim is to investigate the 24/7 continuous operation process with regard to different fermentation residues from agriculture as well as the food industry and to analyze and further optimize the process under real long-term operation conditions. In addition to the optimization of the operating parameters, the focus is on the analyses of the product quality and the membranes used for the process.