1st Arab-American Frontiers of Sciences, Engineering, and Medicine Symposium Kuwait Institute for Scientific Research and the U.S. National Academies

Transcription

1 Linkages: Water and Renewable Energy Recovering Ammonia for Hydrogen Biofuel Production during Anaerobic Digestion Donna E. Fennell Rutgers University, New Brunswick, NJ, USA 1st Arab-American Frontiers of Sciences, Engineering, and Medicine Symposium Kuwait Institute for Scientific Research and the U.S. National Academies October 17-19, 2011 Kuwait City

2 Funding Acknowledgements Dr. David Babson Contributors Miss Xian Huang Miss Liang Chen Collaborators Prof. Lily Young Prof. Uta Krogmann Dr. Valdis Krumins Prof. Shaurya Prakash The Ohio State University

3 Background Water and Renewable Energy Renewable energy efforts mayhave unforeseen environmental consequences for local water supplies and wastewater treatment t tsystems.

4 Water and Renewable Energy Ensuring neutral environmental consequences for renewable energy applications is critical for movingthese technologies forward. We need to be (more) sustainable

5 Anaerobic Digestion Advantages Established technology for many wastes sludges, solid waste, manures, food and crop wastes Scalable Methane has existing infrastructure/end uses Disadvantages Conversion efficiency is low Process can be finicky N and P are liberated Residuals need further treatment and disposal High T ech Low Te ech

6 How Does It Work? Methane (Biogas) Biomass Feedstock anaerobic digester Residual (Undigested Biomass plus Microbial Cells)

7 Anaerobic Digestion of Biomass

8 Ammonia and C:N Ratio C:N Ratio Slaughterhouse waste Human waste Cttl Cattle manure Swine manure Mixed Food wastes Hay general Horse manure Corn silage Olive husks Fruit wastes Race Horse manure Leaves Shrub trimmings Corn stalks Refuse Straw oat Straw general Paper pulp p Straw wheat Hard wood bark Soft woods Corn cobs Rice hulls Paper fiber sludge Newsprint After: On farm Composting Handbook. Cornell. Characteristics of Raw Materials Ammonia released is a function of the organic nitrogen in the feedstock The C:N ratio is the ratio of carbon to nitrogen (g/g)

9 C:N Ratio and Ammonia Toxicity As C:N ra o the total ammonia nitrogen (TAN) TAN as low as 1.5 g/l may inhibit digester microbial communities To control ammonia toxicity Increase feedstock C:N Ammonia/Ammonium NH 3 + H + NH 4 + Total Ammonia N (TAN) Remove ammonia NH 3 + NH + 4

10 The Nitrogen Cycle NO2 NO3 organic g N NH3 NO2 NO N2O N2 Image modified from 2010 Nature Education

11 Ammonia Ammonia causes eutrophication and is toxic to aquatic life, so it must be carefully managed Used as a fertilizer Treated/removed In population centers far from agricultural systems, use as fertilizer may not be economical or energy efficient Net food importers Net nutrient importers Traditional treatments are aerobic, energy intensive i processes

12 To remove NH3 energy/mass inputs are required NO2 O2 energy in NO3 organic N C source in NH3 NO2 NO N2O N2 Image modified from 2010 Nature Education

13 Aerobic Treatment to Remove Ammonia

14 Our work considers NH 3 an energy output Is There Another Way? Methane Biomass Feedstock anaerobic digester Ammonia Hydrogen Residual

15 Approach Anaerobic Digestion Bioammonia to Hydrogen (ADBH) System Could bioammonia liberated during anaerobic degradation of biomass be converted to hydrogen, as part of an integrated anaerobic digestion system? Is the energy balance favorable for this process? Establish theoretical design and conduct energy balance

16 ADBH System: Three Integrated Systems Anaerobic Digester (12) (3) Anaerobic Digester System Solid/Liquid Separator ph Shift (7 11) (5) (6) C Ammonia NH 3 Stripper Recovery System V (7) (8) (9) (13) ph Shift (11 7) Ammonia Split Reforming (11) System (15) (10) Ammonia Reformer (Microcombustor)

17 Trial Variable Inputs Parameter Description Dry Solids Flow Degradable Organic Fraction (DOF) Moisture Content (wt.% water) Aqueous Ammonium Loading Percent Recycle Ambient Digester Temperature Difference InternalHeat and Power Efficiency C:N Ratio InputValue 1,000 kg/hr % 100 mg NH 4+ N/L 65.0% 40.0 K Variable (3.0 to 136)

18 ADBH System: Anaerobic Digester (1) Organic Feedstock Inputs and Outputs (2) Additional Liquid Energy Heat o Influent heating Heat (kj/hr) Anaerobic o Heat loss across Digester the digester Mixing (kj/hr) (3) Digestate boundary Slurry Mixing Biogas (11) (12) Liquid Recycle

19 Stoichiometry of Biomass Conversion Fermentation and respiration of organic matter End products, e.g. NH 4+, CH 4, CO 2 Energy Nutrients Microbe Microbe Microbe New cells Overall Stoichiometry C a H b O c N d + (2a + d c 0.45 e f s 0.25 e f e ) H 2 O (0.125 e f e ) CH 4 + (a c e f s e f e ) CO 2 + (0.05 e f 05 s ) C 5 H 7 O 2 N + (d 0.05 e f s ) NH 4+ + (d 0.05 e f s ) HCO 3

20 C:N Ratio and TAN TAN (m mg/l) Feedstock C:N Ratio

21 ADBH: Ammonia Recovery System (5) Digestate leachate NH 4(aq) and NH 3 (aq) leachate NH Inputs and Outputs + (10) NH 3 (g) ph Shift (7 11) Q = kj/mol- Ca(OH) 2 Power = kj/kg-(aq.) V = Vaporizer C = Condenser (6) C (9) 3 (aq) Condensed NH 3 (aq) NH 3 Stripper V (12) Liquid Recycle to digester Alkaline leachate N removed (8) (7) Stripping Liquid to vaporizer Energy Stripping Steam Stripping power Mixing enthalpy in ph shift reactors Velocity gradient (13) mixing in ph shift Enhanced Biogas reactors ph Shift (11 7) Q = kj/mol- Ca(OH) 2 (14) Liquid Discharge (11) Biogas from digester

22 ADBH: Ammonia Reforming System Chemistry Combustion to heat catalyst CH O 2 (Air) CO H 2 O Consume some methane from biogas to remove Reforming 2 NH 3 (g) N 2 (g) + 3 H 2 (g) ammonia and produce hydrogen biofuel

23 Conclusions Conclusion Thebioammonia to hydrogen process could increase the total energy recovery compared to the methane potential alone for digesters operated with feedstocks with C:N ratios less than ~17

24 Ammonia Release During Digestion Cum mmulative Metha ane (ml) Methane Ammonia (a) Ammonia (mm) Ammonia is released rapidly from proteins and urea 0 0 Ammonia (mm M) Time (days) (b) Time (days)

25 Implications Methane manures anaerobic digestion human waste AMM MONIA BIOM MASS crops, residues nitrification nitrification denitrification crop application precipitate i it t waste food, msw Residual

26 Implications Methane waste food, msw Residual X X AMM MONIA BIOM MASS Traditional treatment is manures expensive i For urban / suburban centerscrops, farresidues from anaerobic land/crop nutrient digestion demand, fertilizer use may nothuman bewaste energetically or economically favorable nitrification nitrification denitrification crop application X precipitate i it t

27 Implications Methane digestion human waste nitrification nitrification denitrification AMM MONIA BIOM MASS A new paradigm manures considers id waste t ammonia as an energy source crops, residues anaerobic crop application precipitate i it t hydrogen waste food, msw Residual