BIOGAS : Combined biogas and bio-ethanol production for optimal energy utilization



 Title of the project

Combined biogas and bio-ethanol production  for optimal energy utilization




Åsa Davidsson, PhD Researcher, Department of Chemical Engineering, Lund University, Sweden


- Anox Kaldnes, Klosterängsvägen 11A, SE-226 47 Lund, Sweden
- BioMil AB, Trollebergsvägen 1, SE- 222 29 Lund, Sweden
- Sekab E-Technology, SE- 891 26 Örnsköldsvik, Sweden
- Primozone Production AB, Terminalvägen 2, SE-246 42 Löddeköpinge, Sweden


Two years
2010- 2012


Until now, much research work has been dealing with facilitating the production of bio-ethanol from 2nd generation feedstocks (i.e. lignocellulosic materials such as wood or straw) with the natural focus on bio-ethanol production. However, environmental sustainability is necessary; the process is generating waste streams that could possibly be converted into biogas which could be used as vehicle fuel to replace fossil fuels. At the same time as biogas is produced, a wastewater handling problem could be solved. This solution is expected to work out well, but so far, not much research work can be found on this matter… therefore, the aim of this R&D project is to evaluate parameters needed to develop an environmental sustainable wastewater treatment  process that uses the waste stream from the 2nd generation bio-ethanol production. Anaerobic treatment will substantially reduce the organic content, but there will still be too high levels of organic matter in the wastewater for internal recirculation and/or direct discharge to any recipient. Hence, combinations of aerobic wastewater treatment and advanced oxidation methods (e;g. ozonation) will be applied after the anaerobic digestion(AD) process. Different combinations of aerobic treatment and advanced oxidation will thus be evaluated. The aim is to reach a water quality that fulfills outlet demands and/or recirculation demands. The research work will include the investigation of: 1Stillage characterization/content; nutrients, toxic substances, organic content, variations in flow and content, etc…,2Adaptation of anaerobic applications3Process parameters,4Combination of AD and aerobic wastewater treatment.


This experimental work aimed to evaluate possibilities for combining bio-ethanol production with anaerobic and aerobic treatment. Some parameters should be characterized.

Nitrogen and phosphorus contents of the waste streams are rather low, and there is a risk of lack of N and P in anaerobic digestion. This lack could be recovered by co-digestion with e.g. food waste. This combination was tested with good results.

Significant amounts of biogas production from bioethanol waste streams are possible, with different biogas production rates and final biogas potentials from different process configurations.

Both mesophilic and thermophilic digestion is possible with no difference in biogas potential.

The overall energy potential from biogas production from different process configurations is about the same for the cases evaluated.

Bio-ethanol residues are inhibiting nitrification, but less after anaerobic digestion. Anaerobic step should precede an eventual aerobic step, and in that way, brings another benefit: the organic content of the waste streams can primarily be used for biogas production, instead of demanding energy for aerobic degradation.



Åsa Davidsson - Lund University