Proces imbalance in biogas plants.

Transcription

1 Proces imbalance in biogas plants. Strategies for preventing breakdown and recovery of the biogas process Henrik Bangsø Nielsen Biogasforum, seminar, 14/6-26

2 Outline Project strategy Resume of last presentation ( ) 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 Overall project strategy A B Visits at biogas plants Data collection C Experiments and results that can be 1) directly related and used by specific plants and 2) can be published

4 A: Visits at biogas plants 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

5 B: Data collection 3,5 daily 1 per. Mov. Avg. (daily) 2 per. Mov. Avg. (daily) 3, methane (m3/m3 reactor vol.) 2,5 2, 1,5 1,,5, date Foaming starts april 23 Foaming ends march 25

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 Blood from pigs added from 1. of September 25 Slow inhibition of biogas production observed in the beginning of October Biogas production constituted only 4% of normal production at the 8. of november Inhibition a combination of increasing ph and ammonia m 3 /(m 3 re a c tor v ol.) okt okt- 5 Biogas production 2-okt okt- 5 3-nov- 5 1-nov nov nov- 5 m M VFA concentration nov-5 14-nov-5 19-nov-5 24-nov-5 Acetat Propionate Isobut. Butyrate Isoval. Valerate

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.5 and 1. g/l Inhibition level at 55 o C: <.5 g/l 37 Degree 55 Degree production (ml CH4/ml sample) production (ml CH4/ml sample) 12 1,5 g/l 8 1 g/l 5 g/l 6 1 g/l 4 2,5 g/l 1 g/l 5 g/l 1 g/l time (days) time (days)

9 Related experiments Digestion at different temperatures in lab-scale reactors CH4 yield (ml CH4/gVS) biogas prod. (ml /ml feed) VFA (mm) ph free ammonia(gn/l) Total VFA acetic propionic 1 isobutyric butyric 5 isovaleric valeric time (days) 8,2 8 7,8 7,6 7,4 7,2 7 1,,8,6,4,2, time (days) 37 o C 55 o C Threshold value for the Thermophilic reactor was 3.8 gn/l and.7-.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 13 Ml methane/g VS Conclusions: Work at mesophilic temperatures or measure VFA frequently CH4 yield (ml CH4/g VS) biogas prod. (ml/ml feed) VFA (mm) p H free ammonia (g- N/l) ,,8,6,4,2 8,5 8 7,5 7 acetic isobutyric butyric isovaleric valeric propionic, time (days)

10 Related experiments VFA surveillance of the plant Acetat/propionat (mm) Minkfedt Total syre (g/l) dato acetat Propionat Total syre Total syre

11 Related experiments Reactor experiment with lipids mlbiogas 5 R1 biogas production ml biogas 5 R2 biogas production Day 6: 5% lipid (W/W) were added = 5% 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 Recovery of the process following process imbalances What now? 2,5 methane (m3/m3 reactor vol.) 2, 1,5 1,,5, date

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 1: Inoculum 2: Manure 3: LCFA or ammonia at steady biogas production Set-up Mixture

15 Recovery of the biogas process Long chain fatty acids inhibition Identification of oleate inhibition level CH4 (ml/gvs) control oleate 3gVS/L oleate 5gVS/L oleate 7gVS/L inoculum and oleate 3gVS/L mixture + BA media + oleate 3gV/L Oleate addition days

16 Recovery of the biogas process Long chain fatty acids inhibition 1 no inhib. inhib no recov. recov water dilution recov.inoc dilution recov manure dilution Test of strategies 118 ml CH4/gVS initial 1 1 Day 4 Day 7 bef. Inhib Inhib + 3 Bef. Recov Inhib + 7 Recov + 4 Inhib + 13 Recov + 1 Inhib + 21 Recov + 18 Inhib + 31 Recov + 28

17 Recovery of the biogas process Long chain fatty acids inhibition Inhibition 5gVS oleate/l with different inoculum/manure ratio 6 ml CH4/gVS inoc 25/ man 15 inoc 11/ man 29 Inhibition days

18 Pulses with oleate m ethane m l/gvs g/l 1. g/l 2. g/l 2. g/l R1 TS/VS = 2.9/2.1% Effect of TS/VS m ethane m l/gvs g/l 1. g/l R2 TS/VS = 5.4/4.1% 2. g/l acetate mm time (days) propionate mm acetate mm time (days) p rop io n a te m M

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 1 no inhib. TN=3.g/L Test of strategies 932 inhib. TN=7.g/L inhib+water dilution TN=3.5g/L inhib+inoc dilution TN=5.2g/L inhib+manure dil. TN=4.6g/L ml CH4/gVS initial 1 inhib+ph decrease TN=7.g/L Prodution rates day 9 to 12 Control: + 5 ml Inhibition: + 26 ml 1 Day 5 Day 9 bef. Inhib inhib+3 / bef. Recov inhib+6 / recov+3 inhib+16 / recov+13 inhib+29 / recov+26 inhib+41 / recov+38

21 Recovery of the biogas process Ammonia inhibition Utilization of biogas potential Effienciency as a function of N-content ml CH theorical level experimental level efficiency % no inhibition w ater dil. manure dil. inoculum dil. no recovery 1 75 no inhibition inhibition no recov. recov w ater recov inoc recov manure 7 2,5 3,5 4,5 5,5 6,5 7,5 N content (gn/l) No inhibition No recovery Water dilution Inoculum dilution Manure dilution % of theoretical level Final N-content 3 7 3,5 5,2 4,6

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-25) Thank you for your attention!!!!

24 Waste index Waste type Blood from pigs Blood from pigs Shrimp sludge Shrimp sludge Meat and Bone meal Meat and Bone meal 1% Fat, DAO Flotations fedt, pigs Bakery (mainly fat) Flotationsfedt, pigs Flotationsfedt, pigs Limfedt (fat) Food waste (fat) Flotationsfedt, chickens Temperature 37 o C 55 o C 37 o C 55 o C 37 o C 55 o C 55 o C 55 o C 55 o C 55 o C 55 o C 55 o C 55 o C 55 o C Inhibition level g VS/l = kg VS/t,5-1, <,5 1,-5,,5-1, 1,-5,,5-2, <1,,5-1, 5,-1, 5,-1, 5,-1, 5,-1, >1, >1,