Case study 3

In case study 3, biomass waste is treated in a three-step process.


  • Organic acid production :

First, a mixture of C-rich industrial wastes and grey wastewater are used to produce organic acid, e.g., citric acid and itaconic acid, via yeast-based biotechnological process. 

Citric acid production with Yarrowia Lipolitica (C) UFZ
The yeast Yarrowia lipolytica an OA producer (Source: A. Aurich / UFZ)
CA production by Yarrowia lipolytica under sterile and non-sterile conditions

- Combination of Waste frying oil + Oil & fat separator discharge --> high citric acid concentration (137-145 g/L), selectivities and productivities 

- Non-sterile bioprocess compatible with sterile one






  • Biogas production :

In the second step, after extracting citric acid from the mixture, residues are used for biogas production through co-digestion with industrial C-rich substrate. As an output of this process, biogas is produced for power generation or heating.

Biogas production
Anaerobic co-digestion demo plant © UFZ
One stage Anaerobic co-digestion results

Fermentation continuous experiments at demo scale

Running experiment: 95 % waste frying oil & 5 % concentrated biomass


  •  Hydrothermal carbonisation :

In the final step, the anaerobic sludge will be treated in a hydrothermal carbonization (HTC) process transforming waste biomass to valuable ready-to-use soil fertilizers.

Hydrothermal Carbonisation
HTC demo plant (C) RENERGIE

The combination of these processes enables material and energetic waste recycling, thus contributing to closing life cycles in the bio-economy. 

Process results are excellent and indicate that the INCOVER yeast-based process is a very suitable option for organic acid and biogas production. Current activities are devoted to optimising the yeast bioprocess. This case study is being implemented in Germany. 


  • Process flow diagram