German researchers affiliated with the University of Hohenheim see grass as a new protein source that can be used for pig and poultry farming. In the ProGrün project, they are not only investigating how grass can be used to obtain high-quality protein for poultry and pig feed, but also for a range of other high-quality materials.
Grass contains a lot of protein, but without processing only ruminants such as cattle and sheep can make good use of it. If the protein is released via a biorefinery technique, it is in principle also suitable as feed for non-ruminant animals, the researchers from the University of Hohenheim have shown in the ProGrün project. The rest of the biomass can also be used. For the production of high-quality materials, but also for the generation of heat and energy.
For the research, a biorefinery demonstration installation was built at the agricultural science experimental station of the University of Hohenheim at the “Unterer Lindenhof” research site, which made it possible to test the entire process on the scale of a pilot plant. The herb is first shredded and pressed. The result is a pressed juice with a high content of soluble proteins, a residual amount of carbohydrates and other chemical compounds. The solid components and about two-thirds of the protein remain in a pressed cake.
Sugar, acids and other substances in the pressed juice can affect the digestibility of the proteins. Therefore, these are largely separate. The proteins are then gently dried, mixed with other feed ingredients and pelletised. In this way it is possible to produce protein-rich feed with 1,000 kilograms of protein from around 45 tons of freshly mown grass. The amino acid composition in the protein extract approximately corresponds to that of soy. Therefore, it is ideal for feeding chickens and pigs.
According to the researchers, it should eventually be possible to use the obtained protein extract for human consumption as well. Pressed board can be used to make paper or fiber mats for insulation. Since it still contains sufficient protein, the pressed cake is also suitable for cattle feed. It can also be used in a biogas plant. The digestate can then serve as a fertilizer. The carbohydrates and sugars in the pressed juice are a promising starting material for the production of platform chemicals such as HMF, which forms the basis for the production of bioplastics.
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