1. Proces imbalance in biogas plants. Henrik Bangsø Nielsen Biogasforum, seminar, 14/6-2006 Strategies for preventing breakdown and recovery of the biogas process

2. Outline  Project strategy  Resume of last presentation (29-11-05)  Follow up on last presentation  Digestion of blood (Lemvig biogas plant)  Ongoing experiments:  Process recovery following ammonia and lipid inhibition  Comments from the audience ?

3. Visits at biogas plants Data collection Experiments and results that can be 1) directly related and used by specific plants and 2) can be published AB C Overall project strategy

4. Main conclusions:  “No problems”  Pre-storage tanks are not useful  Substrate composition is unknown  Substrate degradation characteristics is unknown  Inadequate surveillance, especially with regard to VFA A: Visits at biogas plants

5. B: Data collection Foaming starts april 2003Foaming ends march 2005

6. C: Experiments and results  Pre-storage tanks are not useful: Plant constructors  Substrate composition is unknown and substrate degradation characeristics is unknown: E and R: Screening of various wastes with regard toxicity and biogas potential. Establishment of waste index.  Inadequate surveillance, especially with regard to VFA E and R: VFA surveillance and development of VFA sensors

7. Follow up on last presentation Digestion of blood at Lemvig biogas plant Biogas production VFA concentration  Blood from pigs added from 1. of September 2005  Slow inhibition of biogas production observed in the beginning of October  Biogas production constituted only 40% of normal production at the 8. of november  Inhibition a combination of increasing pH and ammonia

8. Related experiments Substrate characterization in batch Degradation more effective at 37 o C than at 55 o C Inhibition level at 37 o C: between 0.5 and 1.0 g/l Inhibition level at 55 o C: < 0.5 g/l

9. Digestion at different temperatures in lab-scale reactors Related experiments 37 o C 55 o C Conclusions: Work at mesophilic temperatures or measure VFA frequently Threshold value for the Thermophilic reactor was 3.8 gN/l and 0.7-0.9 g free Ammonia-N/l. At mesophilic conditions it Was possible to work at an Ammonia concentration of 4.7 gN/l with a yield of 130 Ml methane/g VS

10. VFA surveillance of the plant Related experiments

11. Reactor experiment with lipids Day 60: 5% lipid (W/W) were added = 50% VS = no inhibition Day 87: 25% lipid (w/w) were added = 85 VS = inhibition Conclusion: plant added more lipid than allowed (25% TS)

12. Ongoing experiments What now? Recovery of the process following process imbalances

13. Recovery strategies  Stop feeding (the process recovers automatically).  Continued feeding with manure (addition of fresh substrate to keep up the biogas production)  Continued feeding with substrate adaptation will occur)  Re-inoculation with effluent (addition of new microorganisms)  Dilution with water (inhibiting compound is diluted)

14. Recovery of the biogas process Set-up Mixture 1: Inoculum 2: Manure 3: LCFA or ammonia at steady biogas production

15. Recovery of the biogas process Long chain fatty acids inhibition Oleate addition

16. 1180 Recovery of the biogas process Long chain fatty acids inhibition Test of strategies

17. Recovery of the biogas process Long chain fatty acids inhibition Inhibition days

18. 0.5 g/l 1.0 g/l 2.0 g/l time (days) Pulses with oleate Effect of TS/VS

19. Recovery of the biogas process Long chain fatty acids inhibition Conclusions:  Using one of the strategies could stimulate the recovery of the process  Following inhibition with LCFA, the recovery proceeded fastest when the biomass was diluted with manure.  The fast recovery with manure could be due to a higher concentration of TS/VS (fibers) However, what about reactor experiments!!!

20. Recovery of the biogas process Ammonia inhibition Test of strategies Prodution rates day 9 to 12 Control: + 50 ml Inhibition: + 26 ml

21. Recovery of the biogas process Ammonia inhibition No inhibition No recovery Water dilution Inoculum dilution Manure dilution % of theoretical level9674927799 Final N-content373,55,24,6

22. Recovery of the biogas process Ammonia inhibition Conclusions:  The recovery of the biogas process following sn smmonis inhibition was strongly related to the ammonia concentration.  Addition of fresh manure gave the best recovery (lower ammonia concentration, fresh substrate) However, what about reactor experiments!!!

23. Acknowledgements Thanks to Sonia Guldener, Henar Meer de Soto and Elena Pueyo Abad for sharing their results. Thanks to Hector Garcia and Prasad L. Kaparaju for their technical assistance The work is supported by Energistyrelsens Energiforsknings-program (EFP-2005) Thank you for your attention!!!!

24. Waste typeTemperatureInhibition level g VS/l = kg VS/t Blood from pigs37 o C0,5-1,0 Blood from pigs55 o C<0,5 Shrimp sludge37 o C1,0-5,0 Shrimp sludge55 o C0,5-1,0 Meat and Bone meal37 o C1,0-5,0 Meat and Bone meal55 o C0,5-2,0 100% Fat, DAO55 o C<1,0 Flotations fedt, pigs55 o C0,5-1,0 Bakery (mainly fat)55 o C5,0-10,0 Flotationsfedt, pigs55 o C5,0-10,0 Flotationsfedt, pigs55 o C5,0-10,0 Limfedt (fat)55 o C5,0-10,0 Food waste (fat)55 o C>10,0 Flotationsfedt, chickens 55 o C>10,0 Waste index