Green Biorefinery - Separation of Lactic Acid from Grass Silage Juice (Brown Juice)

Development of a technical process to separate lactic acid from Brown Juice. Lactic acid is a promising chemical commodity which may be produced from silage juice at low costs and in an environmentally friendly way for subsequent synthesis of valuable products.

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 bio-based 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.

Content and targets of the module

Lactic acid (LA) has the potential to become a very large-volume commodity-chemical intermediate obtained from renewable carbohydrates by fermentation. It can be used as a feedstock for biodegradable polymers, oxygenated chemicals, environmentally friendly "green solvents", plant growth regulators and special chemicals. LA is the basis for a diverse sustainable industry with a high economic potential. Solid State Fermentation (SSF) is obviously an alternative process at low costs. Especially, Silage fermentation of green biomass (grassland) can be optimized by the application of LA-bacteria to generate LA not only for preservation but as economically relevant raw material. The exploitation of LA from Silage has not been a comprehensive research topic yet. In the frame of the Green Biorefinery research focus basic know how for down-stream processing by membrane technology and chromatography is elaborated. Process units should be found to separate Lactic Acid and Amino Acids (AA) from Silage-Juice. Another task is to upgrade the recovered LA into Aminiumlactate and Ethyllactate.

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 and ...
  • 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.


Silage Press Juice is composed of (in % Dry Matter) about 30% Lactic Acid (LA), 8 to 22% Sugars, 25 to 34% Crude Protein (CP) and 23 to 30% Crude Ash. About 85 to 100% of CP is conformed as free Amino Acids (AA). As the raw material is prewilted grass silage (27 to 48% DM in 2001) fractionation (pressing) is demanding and presses must be of special construction. Within this project comprehensive pressing experiments could be carried out in the seasons 2001 and 2002. The trials resulted in sufficient silage juice with an average yield of about 50% Lactic Acid in 2001. In 2002 the experiments were done with larger humidity (20% DM Silage) and double pressing including moistening of the first press cake. With this constellation the Lactic Acid yield could be increased to 85%. As a result the fractionation unit should be installed as a basis pilot plant for further testing in a continuous system.

As the CP is conformed as free Amino Acids down-stream processing of the LA is more demanding. The suggested units, centrifugation and ultra filtration can not be seen as suitable. Although, ultra filtration can be applied for clarification of the silage juice. However, post-fermentation of the silage juice to convert the sugars into additional LA has been found to be an interesting method to increase the efficiency of a Green Biorefinery. Due to the complexity of down-stream processing with S. Novalin (Dep. of Food Technology, BOKU) a new research partner has been involved during the project. With him different processes for down-streaming could be developed and tested. The suggested alternatives are combinations of membrane technology (ultra and nano filtration and electrodialysis) and chromatography. A two-stage electrodialytic separation of valuable substances such as Lactic Acid and Amino Acids was investigated. The total Lactate recovered was 91% at a 98% of demineralization level. In combination with chromatography it should be possible to recover different valuable fractions. On the other hand the production of Aminiumlactata is not satisfactory by applying silage juice. Experiments regarding Ethyllactate show that additional research will be necessary to develop a more sustainable process by using solid catalysts and a more efficient method to remove process water. The economic assessment could be carried out to determine the maximum allowed costs for product down-streaming.


The composition of Silage Juice with Lactic Acid and Amino Acids shows great economic potential. Although the isolation of LA and AA is more demanding by means of down-stream processing a feasibility study within this report shows enough financial scope for investments in separation technology. However, different process alternatives could be proofed successfully. To increase sustainability the process for the production of Ethyllactate as a "green solvent" should be improved as well. 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 constitute 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 and the construction of a pilot plant 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 Glrundlagen der Verfahrens- und Anlagentechnik, TU Graz
  • Dr. rer. nat. Birgit Kamm
    Universität Potsdam, Inst. für Org. Chemie und Strukturanalytik; FG BioOrganische Synthesechemie,
    Forschungsstandort TELTOW-SEEHOF

Co-operation partner economy

  • Dipl.-Ing. Dr. Michael Koncar
    VTU-Engineering GmbH
  • Dipl.-Ing. Werner Lorenz
    LactoProt AG

Co-operation partner science

  • Univ.-Doz. Dr. Karl Buchgraber
    Bundesanstalt für alpenländische Landwirtschaft (BAL) Gumpenstein,
    Institut für Pflanzenbau und Kulturlandschaft
  • Univ.-Ass. Dipl.-Ing. Dr. Herbert Danner
    Abteilung für Umweltbiotechnologie, IFA Tulln
  • Dipl.-Ing. Michael Mandl
    JOANNEUM RESEARCH Forschungsgesellschaft mbH, Regionale Innovations- und Forschungsstelle Hartberg

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