Green Biorefinery - Phase 3: Development of technologies for intensification of process concerning extraction and utilisation of lactic acid, amino acids and gras fibres

Optimisation of downstream processing of a Green Biorefinery for separating lactic acid and amino acids out of silage juice applying chromatography; fundamental test for utilising the fibre fraction for hydro-greening and for horticulture substrate.

Short Description




The project targets on the development of a Green Biorefinery based on the feedstock grass silage generating the key products lactic acid (LA), amino acid (AA), biogas and optionally grass fibre applications and products.


The presented R&D work continues the development done so far and focuses on the investigation of chromatography for separating valuable substances like amino acids and lactic acid out of juice fractions. Additionally, the application of grass fibre for landscaping and greening (e.g. greening of slopes in the field of road construction) as well as horticulture substrate is being investigated by means of lab and field tests.

The main focus of the presented work is in the field of performing systemic runs for testing different chromatography resins for separation AA an LA out pre-treated silage juice. The results indicate that the “integrated” separation of LA and AA fraction by means of one single chromatography process seems not feasible. The continued experiments were performed using two different juice fractions, which were either rich on LA or AA. These fractions could be obtained by applying nano-filtration technology.

Chromatography for Separation of amino acids

Based on the investigations with the resin XAD 1600 one can say that a separation in different amino acid fractions is possible. Especially a fraction of hydrophobic amino acids Leucin/Isoleucin is achievable. Under usage of the resin XAD 1600 the separation-behaviour of Leucin/Isoleucin only depends to a small degree on the pH-value. However, the separation of individual amino acids is not possible under the chosen process conditions. The usage of UBK 530 resin in K+-form perhaps seems to generate an overlay of ionexchange, ionexclusion and complex-building-effects. For the investigation of this phenomenon in detail additional investigations must be carried out. However, the separation of individual amino acids by usage of UBK 530 resin in K+-form is not possible under the chosen process conditions. At pH = 4 the amino acids Glutamate and Aspartate appear in their anionic form. Therefore they can exchange itself with the coordinated-bound SO42- on the stationary phase which could cause adsorption of the amino acids. Perhaps here a partial ion-exchange takes place. To clarify this issue additional investigations must be made. However, due to the separation-behaviour of this type of resin an amino acid separation relevant for process technology cannot be achieved. The separation-result from ODS-A reversed-phase-material shows, that no significant retention of the majority of the amino acids and monosaccharides takes place. The partially hydrophobic amino acids Leucin, Phenylalanine and Tryptophan interact with the stationary phase, which causes a significant retention of these amino acids. The recovery rate of the separated amino acid Phenylalanine is only 16 %. Due to this result the obtained separation-behaviour of the amino acids Phenylalanine by usage of ODS-A resin must be classified as insufficient.

It seems that ion-exchange, ion-exclusion and complex-building-effects take place simultaneously due to usage of MDS 1368 Ca2+ -conditioned resin. A separation of the amino acids Aspartate and Glutamate relevant for processtechnology is acievable only at a higher retention-time. The amino acids Threonine, Serine, Valin, Glycine, Asparagin, Leucine, Isoleucine could only be separated in groups by using this type of resin.

Chromatography for Separation of lactic acid

The aim of the investigations was to recover lactic acid in undissociated form from grass silage juice. For this purpose, chromatographic separation using neutral polymeric resin Amberlite XAD 600 was investigated. The important factors affecting separation performance were investigated with model solutions. The obtained results showed that lactic acid solutions with the purity varying from 93.2 to 99.9 % could be obtained at the recovery yields over 99.4 %. After experiment with the model solutions, the separations with grass silage juices were further processed. Due to the complex composition of the silage juices, the purity of products decreased to 94 % at the recovery yield of 97 %. Although 99 % of inorganic salts and sugars were separated from lactic acid organic acids in general and acetic acid in particular caused a lower purity. It seems that organic acids could not be separated from lactic acid by neutral resin Amberlite XAD 1600. Besides the organic acid problem, some amino acids were remained in the products as impurities.

Utilisation of grass fibre

A field study investigated the technical feasibility of applying grass press cake in hydro-seeding application. The result an a basic level was positive, but data collected cannot indicate better performance than products already available on the market (“Zellugrün”®), However, economic advantages have been identified for using grass press cake in hydro-seeding in comparison with other fibre fractions.

The use of grass press cake for horticultural application in general performed quite poor. Major problems were identified which highly indicate further processing (washing, disintegrating etc.) of grass fibres for that application. Because of the revenue potential in that sector the application is considered quite challenging.

Process intensification

A further improvement of process chain is also investigated. It targets on a potential increase of lactic acid recovery by running an additional fermentation step with the generated press cake. Intermediate data indicate that second lactic acid fermentation with press cake does not only produce lactic acid but a variety of organic acids and ethanol.

Process set-up

A design of the recommended process set-up for lactic acid and amino acids separation out of silage juice has been developed and is presented for the first scale-up in a pilot plant.

Project Partners

Project management

 Ao. Univ.-Prof. DI Dr. Hans Schnitzer
Institut für Nachhaltige Techniken und Systeme
JOANNEUM RESEARCH Forschungsgesellschaft mbH.

Project collaborator

  • DI Michael Mandl
  • Dr. Michael Lukas
  • Mag. Dr. Marion Reinhofer
  • Dr. Michael Tauber
  • Dr. Herbert Böchzelt

Project or cooperation partner

  • Ao. Univ.-Prof. DI Dr. Senad Novalin, Dr. Vu H. Thang
    Universität für Bodenkultur Wien, Department für Lebensmittelwissenschaften und -technologie
  • DI Doris Astleitner, Univ. Prof. Dr. Florin Florineth
    Universität für Bodenkultur Wien, Institut für Ingenieurbiologie und Landschaftsbau
  • Dr. Stefan Kromus
    Biorefinery Systems
  • Dr. Markus Neureiter
    IFA-Tulln, Abteilung Umweltbiotechnologie
  • DI Wolfgang Glasl
    VTU Engineering GmbH
  • Helmut Gössler
    PDC Verfahrenstechnische Entwicklungsges. mbH
  • Mag. Patricia Novalin-Canoy
    Gradient process technology GesmbH
  • Sabine Herneth
    Herneth Gartenbau
  • Ing. Walter Retschek
    Aquasol Handelsges. mbH
  • Hr. J. Derhaschnig, DI M. Fürnsinn
    Hydrogreen Landschaftsbau GmbH