Green Biorefinery - Separation of Proteins from Grass Juice (Green Juice)

Research and development of the technical process to separate protein from grass juice to gain high-protein concentrate for animal feed by ultra-filtration and other separation technologies.

Short Description

One major motivation for the development of Green Biorefineries in Austria is the improvement or conservation of cultural landscapes i.e. grassland pasture. Due to the restructuring of the European agriculture and the possible reduction of the milk quota huge amounts of forage-grassland could be spare within the next years. Official estimations stress that the available grassland-biomass could amount to 500,000 to 1,000,000 tons dry matter a year only in Austria in future. In case of not utilizing the grassland pasture in future the cultural landscape would diminish significantly. The Green Biorefinery is therefore a technological concept to utilize green biomass as an abundant and versatile raw material for industrial products.

The basic idea of this concept is to utilize the whole green biomass like grass, clover and alfalfa and generate a variety of products that are either valuable products themselves or form the basis for further production lines. Besides biobased materials, energy (via biogas generation) may be supplied by this technology. The KORNBERG INSTITUT and JOANNEUM RESEARCH are committed to elaborate a feasible and sustainable concept. The Biorefinery Project consists of three Modules:

  • Module-1: "Utilization of Grass Fiber"
  • Module-2: "Proteins from Grass Juice"
  • Module-3: "Lactic Acid from Grass-Silage".

The Green Biorefinery offers not only a very high economic potential but may support sustainable development efforts, especially in rural regions. Green Biorefineries could therefore significantly contribute to a sustainable development of the Bio-Industry sector.

Proteins from Grass Juice - Content and Targets of the Module

The best known product which can be obtained from grassland-biomass are Proteins. Protein fractions from alfalfa could be isolated already in 1773. But the production of Proteins from fresh biomass is only possible from Mai to October each year. Thus through the concept of ensiling the green biomass continuous production can be ensured over the whole year. The project's industry partner LACTOPROT AG is very much interested to replace soy protein with GMO-free Grass Juice Proteins in his specialty feed (Milk replacer). As there is almost no literature available, research focuses on the characteristics and suitability of Silage Proteins in comparison to Green Proteins. Therefore, the structure (Proteins, Peptides, free Amino Acids), the necessary Downstream-Technology and the product upgrading will be compared. However, final target is the formulation of a high quality milk replacer or/and the elaboration of alternative products based on Silage- Proteins.

Methods and Data

The research tasks are based on six work packages.

  • Production of the Raw Material (Grass-silage)
  • Chemical Analysis of all Phases
  • Experiments in Pilot plant scale
  • Formulation of possible products and Pilot plant concept elaboration
  • Logistics
  • Literature search and Reporting. Scientific work is mainly based on empiric experiments.

Previous Projects can deliver basic data in a limited amount. Certain Down streaming steps are already carried out in pilot plant scale. IFA-Tulln, Dep. of Food Technology of BOKU and Bundesanstalt für Alpenländische Landwirtschaft are in charge of the chemical analysis of the different product streams. Previous to the experiments all steps are discussed with partner experts. All results undergo economic assessment. This procedure is strongly supported by our industry partners. As a principal only sustainable technologies will be further elaborated to avoid "end of the pipe" measurements.


Green Biomass with medium to high protein content (Clover/Grass, Ryegrass, Permanent Pasture, Alfalfa and Cocksfoot) have been harvested for the experiments in the years 2001 and 2002. Both, fresh green matter and silage, inoculated with lactic acid bacteria, underwent cutting and pressing. During this project two different screw presses with a capacity of up to 500 kg FM/h were used to produce Green and Silage Juices rich in crude protein. In case of fresh matter the recovery rate of crude protein into the juice was about 20 % despite the variation of parameters, in both years. The recovery rate of silage proteins could be increase by 70 % to about 50 % in year 2002. However, the experiments show that only part of the Crude Protein (CP) can be separated either by ultra filtration or by coagulation/centrifugation. The project illuminates the different advantages and disadvantages of the two technologies. All protein products produced show similar characteristics.

Regarding efficiency protein concentrates can only be produced by the utilization of Alfalfa as raw material. Due to the results of a Master thesis (Povoden 2002), done for this project, evidence was found that there is a gap between the so called "crude protein" and the protein which can be separated. Especially in silage juices only 5 to 10 % of the proteins are peptides > 1.2 kD (~ 15 amino acids) and can be isolated. Thus the yield of silage protein is too low as to be separated by the suggested technologies economically.

However, it was possible to yield high quality protein products out of green matter. Drying in a pilot-scale spray dryer could be managed without any major difficulties. Due to the retention time in the ultra filtration system concentrates produced by this technology showed increased contamination by pathogen microorganisms. Thus gentle technologies for sterilization have to be found. All different liquid streams underwent comprehensive chemical analysis. The amino acid profile of the products shows a very high content of essential amino acids. However, Silage Juices offer very high yields and an enormous potential on free amino acids available for separation by innovative technologies.


The production of a protein concentrate from Alfalfa for animal feeding could be realized on basis of this project. As Silage can not be integrated in such a system the feasibility is impaired negatively and the degree of innovation must be considered as low. However, the project shows enormous potential for the separation of amino acids from Grass silage Juices. Although the isolation of amino acids is more demanding by means of down stream processing a feasibility study within this report shows enough financial scope for investments in separation technology. Due to the strategic focus of the Austrian Green Biorefinery and the modular production of amino acids, lactic acids and side products based on Grass silage, the project is considered as a "light house" regarding the program "Fabrik der Zukunft". The results and developed know-how of this project constitutes a leading position of the Austrian Green Biorefinery within Europe. Subsequent and consequent further development of sustainable and innovative Biorefinery technologies based on Grass silage will result in the extension of the innovation leadership.

Project Partners

Project management

Dipl.-Ing.Dr. Christian Krotscheck
Kornberg Institut für nachhaltige Regionalentwicklung und angewandte Forschung
Steirisches Vulkanland Regionalentwicklung GmbH

Project or cooperation partner

  • Ao. Univ.-Prof. Dipl.-Ing. Dr. Michael Narodoslawsky
    Institut für Gl. der Verfahrens- und Anlagentechnik, TU Graz
  • Univ.-Doz. Dr. Karl Buchgraber
    Bundesanstalt f ür alpenländische Landwirtschaft (BAL) Gumpenstein, Institut für Pflanzenbau und Kulturlandschaft
  • Dipl.-Ing. Werner Lorenz
    LactoProt AG
  • Dipl.-Ing. Dr. Michael Koncar
    VTU-Engineering GmbH
  • Christian Hiel
  • Dr. Steffi Dudek
    Inst. für Angewandte Proteinchemie e. V., (ProChem)
  • Dipl.-Ing. Michael Mandl
    JOANNEUM RESEARCH Forschungsgesellschaft mbH, Regionale Innovations- und Forschungsstelle Hartberg
  • Univ.-Prof.DI.Dr. Gerhart Braunegg
    Inst. f. Biotechnologie, TU Graz
  • Univ.-Ass. Dipl.-Ing. Dr. Herbert Danner
    Abteilung für Umweltbiotechnologie, IFA Tulln

Contact Address

Dipl.-Ing.Dr. Christian Krotscheck
Kornberg Institut für nachhaltige Regionalentwicklung und angewandte Forschung
Steirisches Vulkanland Regionalentwicklung GmbH
Haus der Region, Dörfl 2
A-8330 Feldbach
Tel.: +43 (3152) 83 80-23
Fax: +43 (3152) 83 80-4