Production of bioenergy and biochemicals from industrial and agricultural wastewater

1. Production of bioenergy and biochemicals from industrial and agricultural wastewater J.H. Cha

2. 2007 Winter School For MFCs Contents 1. INTRODUCTION 2. Biological methane production from organic material in industrial and agricultural wastewater 3. Biological hydrogen production 4. Biological electricity production 5. Biological chemical production 6. Outlook

3. 2007 Winter School For MFCs Introduction • Sustainable society • reduction of dependency on fossil fuels • lowering of the amount of pollution than is generated • Wastewater Treatment • a paradigm shift; ‘disposing of waste→using waste’ • Wastewater are potential commodities from which bioenergy and biochemicals may be produced. • bio-processing strategies • methanogenic anaerobic digestion • biological hydrogen production • microbial fuel cells • fermentation for production of valuable products Recovery of energy and valuable materials - reduce the cost of wastewater treatment - reduce the dependence on fossil fuels

4. 2007 Winter School For MFCs Biological methane production • Reaction • Methane formation from glucose; C6H12O6↔ CH4 + CO2 • Methanogenic anaerobic digestion • high organic removal rates • low energy-input requirement • energy production (i.e. methane) • low sludge production • UASB • Upflow Anaerobic Sludge Blanket • efficiently retains the complex microbial consortium without the need for immobilization on a carrier material by formation of biological granules with good settling characteristics. • Approximately 60% of the thousands of anaerobic full-scale treatment facilities worldwide are now based on the UASB design concept.

5. 2007 Winter School For MFCs Biological methane production • AMBR • Anaerobic Migrating Blanket Reactor • The organic removal rates are higher than those in UASB. • ASBR • Anaerobic Sequencing Batch Reactor • operating in a four-step cycle • 1) wastewater is fed into the reactor with settled biomass. • 2) wastewater and biomass are mixed intermittently. • 3) biomass is settled. • 4) effluent is withdrawn from the reactor. • The methane has been • used as a fuel source for on-site heating • used as a fuel source for electricity production. • converted to methanol for use in production of biodiesel.

6. 2007 Winter School For MFCs Biological methane production

7. 2007 Winter School For MFCs Biological methane production source: http://www.uasb.org/ • UASB Anaerobic sludge granules from a UASB reactor treating effluent from a recycle paper mill (Roermond, The Netherlands).

8. 2007 Winter School For MFCs Biological methane production source: Angenent et al., Wat. Res. 35(7) pp.1739-1747, 2001

9. 2007 Winter School For MFCs Biological hydrogen production • Biological hydrogen production • It is easy to separate gaseous products from the wastewater. • But, successful hydrogen production requires inhibition of hydrogen-using microorganisms • homo-acetogens, methanogens • propionic acid-producing bacteria; ‘reaction 4’ • ethanol-producing bacteria; ‘reaction 5’ • homoacetogens; ‘reaction 8’ • Inhibition is accomplished by • heat-treatment of the inoculum • operation at high dilution rates or low pH • Hydrogen yield is actually low. • theoretically, 12 moles of hydrogen per mole hexose; ‘reaction 1, 8’ • typically 1-2.5 moles of hydrogen per mole hexose • Escape of hydrogen during scale-up • due to the high diffusivity of hydrogen

10. 2007 Winter School For MFCs Biological hydrogen production • Examples of optimization efforts to maximize hydrogen production

11. 2007 Winter School For MFCs Biological electricity production • Microbial Fuel Cells • In principle, MFCs are compared with hydrogen fuel cells • Several Mechanisms which electrons can be transferred to metals or electrode • Geobacter spp.; periplasmic c-type cytochrome proteins • Shewanella spp.; soluble quinones (as electron-shuttling compounds) • mixed culture; generating higher current than that generated by a pure culture • anodophilic bacteria; Geobacteraceae, Desulfuromonaceae, Alteromonadaceae, Enterobacteriaceae, Pasteurellaceae, Clostridiaceae, Aeromonadaceae, and Comamonadaceae

12. 2007 Winter School For MFCs Biological electricity production • Dual-chamber microbial fuel cells

13. 2007 Winter School For MFCs Biological electricity production • Limitation to implementation of MFCs • Power density is still relatively low. • Technology is only in the laboratory phase. • Potential difference(△E) between the electron donor and acceptor • max. potential of ~ 1 V • However, by linking several MFCs together, the voltage can be increased.

14. 2007 Winter School For MFCs Biological electricity production • To be feasible • Improvement in power density is required. • Construction and operating costs must be reduced. • expensive noble metals in electrodes • soluble or electrode-bound electron shuttles • aeration at cathode compartments • Rates of electron transport to the anode electrode must be improved. • selecting a well-adapted anodophilic microbial community • optimizing the MFC operating conditions • Optimization can be conducted in a systematic fashion only when the mechanisms of electron transfer from microorganism to electrode are better understood. • Reactor size can be small enough to make direct bioelectricity production by MFCs economically viable.

15. 2007 Winter School For MFCs Biological chemical production • major limitation of bio-energy tech. • the relative low cost of the current non-renewable energy source → government subsidies, direct local need to save on energy costs • It cannot entirely satisfy the energy demand of our society. • Therefore, biological chemical production may be more feasible than bio-energy production. • conversion to valuable products • Strategies to enhance bioconversion • improvement of the amount of product formed per reactor volume, per time period • process modification (culture immobilization), coupling two separate bioreactors • separation and purification → the manufacturing cost → more selective, more efficient, and shorter separation routes

16. 2007 Winter School For MFCs Biological chemical production

17. 2007 Winter School For MFCs Outlook • Anaerobic digestion • mature process, economically viable tech. • methane (low value product), catalytic conversion of biogas to syngas • Hydrogen fermentation • great potential as a pre-treatment step • MFC • is exciting, but, fundamental understanding of the microbiology and further development of the technology is required. • Biochemical production • promising process (high-value bio-chemicals might soon be produced from wastewater)

18. 2007 Winter School For MFCs Outlook • Anaerobic digestion • mature process, economically viable tech. • methane (low value product), catalytic conversion of biogas to syngas • Hydrogen fermentation • great potential as a pre-treatment step • MFC • is exciting, but, fundamental understanding of the microbiology and further development of the technology is required. • Biochemical production • promising process (high-value bio-chemicals might soon be produced from wastewater) • optimization (bioreactor design configuration, operating conditions), scale-up

19. Electricity Phosphorous Pre-treatment MFC / SND L-S Separation P Recovery Waste Water Water Melting PF/MF/RO Dewatering Slag 2007 Winter School For MFCs Outlook “The biological oxygen demand in the effluent, which is an indication of how well wastewater is treated, will be too high in all four different bioprocessing strategies, and thus, post-treatment with, for example, activated sludge, is an anticipated requirement. Hence, post-treatment facilities must to be integrated into the design of full-scale bioprocessing operations.” But, We have an alternative !!

20. Any more Questions ?