1. Irini Angelidaki, Kanokwan Boe and Lars Ellegaard

2. Presentation content Biogas in Denmark: A typical Centralized Biogas Plant Main Results of the investigation Conclusions

3. Location of Centralized biogas plants in Denmark

4. Typical centralized biogas plant Ribe biogas plant

5. Full-scale investigation  Process stability  Process efficiency  Microbiology

6. Potential methods to improve recovery efficiency from manure -Increase stabilily of the digestion process -Pre-treatment of incoming substrate (to increase degradability) -Increase retention time of the manure reactor(s) -Arrange post-digestion systems (to increase degradation efficiency)

7. Stability in Danish Biogas Plants

8. Correlation between ammonia and VFA.

9. Residual methane production 55 o C 25 o C 20 o C 15 o C 55 o C 25 o C 20 o C 15 o C

10. Residual methane production

12. Restgastab i forhold til total produktion >15%10-15%< 10%

13. Temperature and residual methane

14. Distribution of the total methane potential

15. Main reactor residual methane loss versus retention time

16. Temperature effect on residual biogas potential

17. INCREASING TEMPERATURE Samples previously incubated at 10  -15  C for a long period have been moved to process temperature (37  -54  C):

18. INNOVATIVE SOLUTIONS SITUATION: The majority of the biogas plants have Reactors with good efficiency; Many plants are loosing a lot and the gap between the theoretical and the practical potential is still wide; MAIN OBSTACLE: hydrolysis is the real rate limiting step for the further methanogenesis  increase HRT to provide a better substrate hydrolysis SOLUTIONS: TRADITIONAL SOLUTIONS INNOVATIVE SOLUTIONS New process configurataion: Utilization of the After-Storage. Increase the HRT in main reactor

19. Conclusions Significant amounts of CH4 are lost (5-30%) Plants with HRT< 15 days are lossing more CH4 from the main reactor Post-digestion is highly influenced by the temperature Post-digestion at low temperature are increasing the total methane potential of the material Manure-plants are dominated by Methanosarcina, while sludge plants by Methanosaeta.

20. Acknowledgements  The study was funded by the Danish Energy Agency,“Development of Renewable Energy”  The operational staff of the Biogas Plants participating in the investigation is greatly acknowledged  Researchers:  Kanokwan Boe  Lars Ellegaard  Dimitar Karakshlev  Damien Batstone  Irini Angelidaki  Students:  Simone Labo  Lucía Fernández García  Eva Arler  He Zhen  Chao Pan  Troels Hilstrøm  Søren H. Laursen  Technicians:  Hector Garcia  Majbrit Staun Jensen