Production of leaf protein concentrates in green biorefineries as alternative feed for monogastric animals

Photosynthetic active green leaves from grasses, legumes and other plants contain in general high amounts of proteins, which can be utilized by ruminants or in many cases are wasted. Extraction of proteins from leaves represents an attractive solution to the increasing demand for protein-rich feed for monogastric animals, while decreasing the dependency on soybean imports. Furthermore, there is an increasing demand for organic products produced without the use of chemical fertilizers, pesticides or other artificial chemicals. Leaf proteins extracted from organically grown crops, especially legumes could be attractive as animal feed. Even though a lot of research was carried out in this field previously, recent technological development and biotechnological advances together with the increasing demand may facilitate the industrial implementation of leaf protein extraction processes nowadays. This review focuses on the concept of leaf protein and its history, the different methods for the extraction of proteins from leaves, and the nutritional value of the leaf protein concentrates for feeding monogastric animals. Furthermore, the review focuses on the potential integration of leaf protein extraction within green biorefineries, where freshly harvested leafy plant material is processed into a broad range of products, including feed, food, chemicals, materials and biofuels. The integration of production of leaf protein concentrates within green biorefineries will encourage the establishment of production facilities, also focusing on utilization of the different residue streams. Thereby such green biorefineries can contribute to the development of more self-sufficient and sustainable agricultural systems in Europe.