study of microbial community dynamics in an anaerobic digestion process intended to produce biogas...

Special Abstracts / Journal of Biotechnology 150S (2010) S1–S576 S25

these data resulted in the first physiological description of how She-wanella respond to glucose and lactate in the presence of oxygenin an operating MFC.

doi:10.1016/j.jbiotec.2010.08.074

[B.42]

Low cost microbial fuel cells for energy recovery from wastew-ater

D. Pant ∗, D. Arslan, G. Van Bogaert, Y. Alvarez Gallego, H. DeWever, L. Diels, K. Vanbroekhoven

VITO - Flemish Institute for Technological Research, BelgiumKeywords: Microbial fuel cells; Wastewater treatment; Energy gen-eration; Low cost materials

In this study, domestic wastewater was given a second lifeas dilution or pretreatment medium for the concentrated wastestreams. Currently, domestic wastewater is treated in conventionalsewage wastewater treatment plants by means of aerobic activatedsludge systems. Energy needs to be supplied at about 15 kWh perinhabitant per year. A direct anaerobic treatment with the recoveryof energy is not feasible since the wastewater is too low in energycontaining compounds and has a low temperature. Therefore, inthis research, this low strength wastewater was first up concen-trated by mixing it with kitchen waste. In the primary treatment,bioreactors optimized to produce volatile fatty acids (VFAs) wereused to treat sewage enriched by the organic fraction of householdwastes (kitchen waste). The biogas produced from these matrices,both at mesophilic and thermophilic conditions was continuouslymonitored, besides hydrolysis of the solids and formation of all fer-mentation products. In the second step, microbial fuel cells (MFCs)were operated using the effluent from the continuous reactor pro-ducing VFAs and biohydrogen. The effluent rich in VFAs specificallyacetic acid was used at different loading rates by diluting it withphosphate buffer solution (PBS). Thus, it was a two-step continu-ous process with VFA/hydrogen being produced in first step andelectricity in the second step in MFC. The combined system wasable to reduce the COD load by 90%. The concentration of VFAswas also monitored regularly and showed a decreasing trend overtime. Further, the open circuit potential of anode changed from−500 mV vs Ag/AgCl to 0 mV vs Ag/AgCl when the VFAs (especiallyacetate) was depleted in the system. However, on feeding the sys-tem again with the effluent, the OCV recovered back to −500 mV vsAg/AgCl. Thus, the overall aim of converting chemical energy intoelectrical energy was achieved. Also, the MFCs involved in theseexperiments used VITO’s in-house developed non platinised Tefloncoated carbon electrode as air cathode and novel permeable mem-branes, replacing the expensive platinum containing electrodes andproton exchange membrane (PEM) such as Nafion. A cost compari-son revealed that the cost of the MFC with these novel materials isone third of the conventional MFCs used by researchers.

doi:10.1016/j.jbiotec.2010.08.075

[B.43]

Study of microbial community dynamics in an anaerobic diges-tion process intended to produce biogas suitable for feeding amolten carbonate fuel cell (MCFC) system

C. Alisi ∗, C. Matano, F. Tasso, E. Massi, R. Ciccoli, A.R. Sprocati

ENEA, ItalyKeywords: Biogas; Microbial community; Fuel cells

The coupling of anaerobic digestion of biomass (AD) with MoltenCarbonate Fuel Cell (MCFC) would enable to improve efficiency inenergy use and increase distributed energy generation. The feasibil-ity of this coupling requires the reassessment of both technologies,in the perspective of their compatibility. This study deals withthe AD microbiology. AD process development has traditionallybeen focused mainly on the plant engineering, disregarding theknowledge about nature and function of the microbial communityinvolved. As a consequence, bioreactor design has been based onempirical criteria, leading to often perform unstable and inefficienttreatments. The molecular approach is currently bridging the lack ofreliable and quantitative information on AD microbiology, reveal-ing a much higher microbial biodiversity than what was knownbefore, using culture-dependent methods only. In this study, a setof lab scale anaerobic co-digestion batch tests of swine manure(SM) and anaerobic sludge (AS) were carried out to identify theconditions yielding the biogas required by MCFC system (methanecontent >70% v/v and low H2S impurity concentration 0,1-5 ppm).

For this purpose microbial communities dynamics have beencompared at different conditions (T: 37 ◦C, 55 ◦C, 65 ◦C and pH: 6and 7). The best condition proved to be 55 ◦C at pH 7: the con-version efficiency of COD into methane was >75% and the H2Scontent was < 50 ppm, higher than the threshold value requiredby MCFC but lower than values referred by literature (up to 1%).Elaboration of PCR-DGGE molecular fingerprinting highlighted acorresponding community structure characterised by a high Simp-son’s diversity (1D) and evenness (Ed) index, both for eubacteriaand archaea, while, for archaea only, a good Range-weighted rich-ness (Rr) and a high functional organisation curve Pareto-Lorenz(Fo). It seems thereof feasible to further guide the microbiologi-cal process towards the production of a biogas suitable for feedingMCFC system.

doi:10.1016/j.jbiotec.2010.08.076