Conversion of Wastes into Bioelectricity Trent Benefield Ryan Risinger microbes-generate-electricity-from-mud.html residential-electricity-tariffs.php 1

Summary Why is this important? MET's (Microbial Electrochemical technologies) Prior Work Electricity Generation Chemical Production in MEC's (Microbial Electrolysis Cells) Compare with conventional technologies Improvements Conclusions References 2

Why is this important? Treating wastewater takes 15 GW power in U.S. Domestic, industrial, and animal wastewater has considerable potential energy (~1.5x10^11 kWh) ~17 GW power equivalent Additional 600 GW power annually from agriculture biomass l 3

MET's Microbial Electrochemical Technologies Use microorganisms to generate electricity and produce chemicals Process able to use wide variety of wastes Acetates, protein, lignocellulose, etc. ss.htm nol_Production.html 4

Prior Work Basic technology has been around since the early 19th century. In 1931 a series of microbial fuel cells was created that produced 31 volts, but the current was only 2 milliamps. Recently in Australia, Foster's Brewing Co. has produced a large scale bioreactor (660 gallons) that uses the brewing process wastewater as a fuel source. It produces clean water and 2 kilowatts of electrical power. 5

Electricity Generation Exoelectrogenic o example: Geobacter, Shewanella Use of "electron shuttles" o Flavin, and phenazine  Electron transport chain Anode: Bacteria release electrons/protons Cathode: Oxygen is oxidizer 6

Wide variety of wastes in process Need variety of microbes More power=more specialized wastes o Acetates, Lactate More complex wastes=more interactions needed to break down molecules o Syntrophic interactions, similar to anaerobic digestion ession=NC_003552&ref=index_12.htmll 7

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Chemical Production in MEC's Microbial Electrolysis Cells Applying power can produce variety of chemicals biofuels, by producing hydrogen o Produced at the cathode o More thermodynamically efficient than water splitting  -.13 V minimum addition, -1.2 V for water splitting Voltage required for Hydrogen production: -.41 V Voltage at anode: -.28 V -.41 V minus -.28 V = -.13 V B. E. Logan et al., Microbial electrolysis cells for high yield hydrogen gas production from organic matter. Environ. Sci. Technol.42, 8630 (2008). 9

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Organic chemicals produced at cathode Apply voltage Methane is most common in MEC's o produced by H 2 evolved at cathode NaOH o Cation exchange membrane separator o Produced due to pH gradients between chambers o Anode: proton build up o Cathode: proton deficiency Hydrogen Peroxide o H 2 O normally produced at cathode O 2 + 2H 2 O + 2e - -> H 2 O 2 + 2OH - 11

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Compare with conventional technologies Current wastewater processing technologies Developing since over a century Requires -0.3 kWh/m^3 electricity Carnot Cycle limitations Membrane bioreactors Requires 1-2 kWh/m^3 electricity Economical with very large digesters only Needs concentrated waste streams Warmer temperatures Low energy recovery Decreasing need for sludge handling S. Hays, F. Zhang, B. E. Logan, Performance of two different types of anodes in membrane electrode assembly microbial fuel cells for power generation from domestic wastewater. J. Power Sources196, 8293 (2011). P. L. McCarty, J. Bae, J. Kim, Domestic wastewater treatment as a net energy producer—can this be achieved? Environ. Sci. Technol.45, 7100 (2011)

Waste TypeHeat of Combustion kcal/kg Charcoal7213 Animal Fats9450 Wood Chips4785 Coffee Waste4371 Acetic Acid3446 Sunflower Stalk4300 Tobacco Waste value.html Examples of Types of Possible Feed pacific.com/WasteToEnergy/BTU_Values.pdf 14

Improvements Increase power output in microbes Addition of Enterococcus faecium increase power output by 30-70% o Little power produced on its own More research required Pretreat incoming biomass Increases digestibility Lime (calcium hydroxide) pretreatment Breaks down lignin in lignocellulose Biomass.htm 15

Conclusion Technology is has lots of potential for energy generation. Current research still can't achieve large electricity generation. Many different feeds with varying potential energies Improvements are still possible (varying microbial cultures, pretreatmment) One of the greatest advantages is to recycle wastewater with drastically less electricity input. 16

References 1.P. L. McCarty, J. Bae, J. Kim, Domestic wastewater treatment as a net energy producer—can this be achieved? Environ. Sci. Technol.45, 7100 (2011) B. E. Logan, Extracting hydrogen and electricity from renewable resources. Environ. Sci. Technol. 38, 160A (2004). 3.R. D. Perlack et al., “Biomass as feedstock for a bioenergy and bioproducts industry: The technical feasibility of a billion-ton annual supply,” vol. ORNL/TM-2005/66, report no. DOE/GO (Oak Ridge National Laboratory, Oak Ridge, TN, 2005). 4.B. E. Logan, Exoelectrogenic bacteria that power microbial fuel cells. Nat. Rev. Microbiol. 7, 375 (2009). 5.E. Marsili et al., Shewanella secretes flavins that mediate extracellular electron transfer. Proc. Natl. Acad. Sci. U.S.A.105, 3968 (2008). 6.H. von Canstein, J. Ogawa, S. Shimizu, J. R. Lloyd, Secretion of flavins by Shewanella species and their role in extracellular electron transfer. Appl. Environ. Microbiol. 74, 615 (2008) /AEM T. H. Pham et al., Metabolites produced by Pseudomonas sp. enable a Gram-positive bacterium to achieve extracellular electron transfer. Appl. Microbiol. Biotechnol. 77, 1119 (2008) /s

8.Logan, Bruce E. and Korneel Rabaey. "Conversion of Wastes into Bioelectricity and Chemicals by Using Microbial Electrochemical Technologies." Science 337 (2012): Print. 9."Microbial Fuel Cell" Wikipedia. n.p., n.d. Web. September 10, P. D. Kiely, J. M. Regan, B. E. Logan, The electric picnic: Synergistic requirements for exoelectrogenic microbial communities. Curr. Opin. Biotechnol. 22, 378 (2011). 11.D. F. Call, B. E. Logan, Lactate oxidation coupled to iron or electrode reduction by Geobacter sulfurreducens PCA. Appl. Environ. Microbiol. 77, 8791 (2011) /AEM A. M. Speers, G. Reguera, Electron donors supporting growth and electroactivity of Geobacter sulfurreducens anode biofilms. Appl. Environ. Microbiol. 78, 437 (2012) /AEM B. E. Logan et al., Microbial electrolysis cells for high yield hydrogen gas production from organic matter. Environ. Sci. Technol.42, 8630 (2008). 14.P. Clauwaert et al., Combining biocatalyzed electrolysis with anaerobic digestion. Water Sci. Technol.57, 575 (2008). 15.P. Parameswaran, H. Zhang, C. I. Torres, B. E. Rittmann, R. Krajmalnik-Brown, Microbial community structure in a biofilm anode fed with a fermentable substrate: the significance of hydrogen scavengers. Biotechnol. Bioeng.105, 69 (2010). 16.R. A. Rozendal, H. V. V. Hamelers, C. J. N. Buisman, Effects of membrane cation transport on pH and microbial fuel cell performance. Environ. Sci. Technol.40, 5206 (2006). 18

17.K. Rabaey, S. Bützer, S. Brown, J. Keller, R. A. Rozendal, High current generation coupled to caustic production using a lamellar bioelectrochemical system. Environ. Sci. Technol.44, 4315 (2010). 18.S. T. Read, P. Dutta, P. L. Bond, J. Keller, K. Rabaey, Initial development and structure of biofilms on microbial fuel cell anodes. BMC Microbiol.10, 98 (2010) /

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