Project meeting of STEP at the site of the company ATS - Agro Trading & Solutions in Hardegsen (Photo: DBFZ)

Heat Power Biogas Biomass furnace

Project ID 03KB116

STEP - Utilization of Straw-based Energy Pellets and Poultry Manure in Biogas Plants with Thermal Self-sufficent Digestate Processing

Straw untreated | Straw after treated with a hammer mill | pelleted | pelleted with NaOH (Photo: Fraunhofer IKTS)


  • 01.08.2016 – 31.01.2019


Fraunhofer Institute for Ceramic Technologies and Systems IKTS
Biomass Technologies and Membrane Process Engineering
Winterbergstraße 28
01277 Dresden

Björn Schwarz – project manager
Telephone: +49 (0)351 2553-7745


03KB116B - DBFZ Deutsches Biomasseforschungszentrum gemeinnützige GmbH
03KB116C - Rückert NatUrgas GmbH
03KB116D - GM Biogas
03KB116E - ATS - Agro Trading & Solutions
03KB116F - A.P. Bioenergietechnik GmbH
03KB116G - REGEB Energieerzeugung und- verteilung Bersenbrück GmbH & Co. KG
  • Address:
  • REGEB Energieerzeugung und- verteilung Bersenbrück GmbH & Co. KG
    Hermann-Kemper-Straße 5
    49593 Bersenbrück
  • Contact:
  • Martin Hülsmann – Projektleiter
    Telefon: +49 (0)5439 9403-11

Associated partners

Cooperation partners


03KB116 - Arnold & Partner Biogas- und Verfahrenstechnik AG


Final report only available in German

Subject and aim

The project focuses on the energetic utilization of poultry manure and straw based on biogas production. In addition to the energy balance (incl. logistics) especially the material potential of the resulting digestate (fertilizer and fuel) is considered or developed.

On the one hand the objective is to proof the practical feasibility of straw-based energy pellets in a large-scale biogas plant and on the other hand further improvement of the energy demand in the tightly focussed treatment of fermentation residues into valuable materials and process water. Furthermore, in addition to the production of fertilizer products a fuel to be produced from fermentation residues which is suitable for direct use in boilers.

At the end of the project design parameters are available for the entire process chain for large-scale implementation.


IKTS analyses and evaluates all input and output flows of the following process stages: substrate pretreatment, fermentation and digestate treatment. Continuous experiments are carried out in the laboratory with regard to the long-term stability with the use of condensates of the evaporation step and the use of straw pellets with sodium hydroxide. Furthermore, the IKTS works conceptually and experimentally in the areas of digestate separation and improvement of the combustion properties.

DBFZ characterises the resulting digestate with regard to their fuel properties. Additional purification steps for digestate are applied in order to minimize the emissions occurring during the combustion. Furthermore small-scale combustion tests up to 100 kW are carried out with complete analysis.

Rückert NatUrgas
Main objectives are minimizing energy consumption and amounts to dispose as well as maximizing value creation through production of valuable materials out of the digestate treatment. For this purpose extensive tests for dewatering before the evaporator stage are organized in practically relevant scale (in particular the removal of fines). In addition, tests are carried out and will be evaluated for the efficient drying of the various intermediates of the digestate.

GM Biogas
GM Biogas operates a 2.4 MW biogas plant with three parallel fermenters. Within the project the amount of supplied corn silage of one fermenter will be changed into straw-based biogas pellets produced in the project.

A demonstration experiment for the production of 250 t straw-based biogas pellets is designed and realised by ATS. That includes organizational and security measures. ATS enables the manufacture of large quantities of pellets from separated, dried and optionally conditioned digestate.

A.P. Bioenergietechnik
The A.P. Bioenergy GmbH deals with the optimization and further development of the combustion step concerning the thermal utilization of untreated and treated digestate. The combustion emissions are significantly reduced by setting and adjusting various parameters. Combustion tests will take place in a pilot plant with up to 400 kWth.

REGEB is responsible for the execution of evaporation tests of digestate liquid phase at industrial scale. For this a four-level system is used. The overall efficiency of the plant is to be increased by supplementing of a pre-degassing step.



  • Analysis (physical, chemical and granulometric parameters)
  • Fermentation (batch and continuous)
  • Treatment and purification of digestate


  • Analysis (fuel)
  • Small scale combustion tests

Rückert NatUrgas

  • Process concepts
  • Dewatering, solids separation digestate
  • Drying digestate

GM Biogas

  • Large-scale use of biogas pellets in biogas plant


  • Pelletizing straw incl. adding NaOH (industrial scale)
  • Pelletizing digestate
  • Pelletizing combustion ash + concentrate of the evaporator

A.P. Bioenergietechnik

  • Digestate combustion in practicable boiler
  • Evaluation and optimization


  • Efficient digestate evaporation in practice scale
  • Evaluation and optimization


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