VALORIZATION OF THE LIQUID FRACTION OF A MIXTURE OF LIVESTOCK WASTE - PowerPoint PPT Presentation

VALORIZATION OF THE LIQUID FRACTION OF A MIXTURE OF LIVESTOCK WASTE AND CHEESE WHEY FOR BIOGAS PRODUCTION THROUGH HIGH ‐ RATE ANAEROBIC CO ‐ DIGESTION AND FOR ELECTRICITY PRODUCTION IN A MICROBIAL FUEL CELL (MFC) I. MICHALOPOULOS, D. CHATZIKONSTANTINOU, D. MATHIOUDAKIS, I. VAIOPOULOS, A. TREMOULI, K. PAPADOPOULOU, M. GEORGIOPOULOU, and G. LYBERATOS School of Chemical Engineering National Technical University of Athens

Livestock Waste and Cheese Whey  Obtained from farms  Main constitution: o High organic content o High concentration of nitrogen o High concentration of phosphorus  Residues of some harmful substances (growth hormones, antibiotics and heavy metals)  Efficient utilization is essential: o in order to protect the environment and avoid the generation of human diseases. o due to agriculture’s high social and economic impact on rural and mountainous regions

Objective  Evaluation of two alternative ways for the valorization of livestock waste and cheese whey: o Biogas production through anaerobic co ‐ digestion in a Periodic Anaerobic Baffled Reactor (PABR) and o Electrical energy generation in a Microbial Fuel Cell (MFC).

The Periodic Anaerobic Baffled Reactor (PABR)  Novel bioreactor  Designed to operate at high organic loading rates  Methanogens can be retained even in the first compartments  Switching frequency  operational flexibility

The Periodic Anaerobic Baffled Reactor (PABR)  Operating volume: 77L  4 compartments of equal volume  Consists of two concentric cylinders of which the interior operated as a bath  35 o C (mesophilic conditions)

Operation of PABR Operation of PABR during a during a period T period T ∙ ∙ B C D A ∙ ∙ Effluent Effluent Influent fluent 0<t<T/4 0< <T/4

Effluent Effluent ∙ ∙ B C D A Influent fluent ∙ ∙ T/4< T/4<t<T/2 <T/2

Influent fluent Effluent Effluent ∙ ∙ B C D A ∙ ∙ T/2< T/2<t<3T/4 <3T/4

∙ Influent fluent ∙ B C D A ∙ ∙ Effluent Effluent 3T/4< 3T/4<t<T <T

The working principle of the Microbial Fuel Cell (MFC) Bioreactor that converts chemical energy, stored in the chemical bonds of organic compounds, directly into electrical energy, through catalytic reactions of microorganisms under anaerobic conditions.  A promising technology for wastewater treatment  No aeration needed  Limited sludge production  Electricity generation DUAL CHAMBER MFC CUBIC MFC TUBULAR MFC

The working principle of an MFC Electricity External resistance CO 2 Catalyst e ‐ H 2 O Bacteria 6O 2 H + Anode Cathode CEM Chemistry of MFC: As an example, glucose is used as an organic substrate. 6CO 2 + 24H + + 24e ‐ Anode : C 6 H 12 O 6 + 6H 2 O Cathode : 24H + + 24e ‐ + 6O 2 12H 2 O

Dual Chamber MFC (H ‐ type) Two bottles (effective volume=250 • ml) connected via a glass tube. Anode electrode: carbon fiber paper • (Toray, 10 w.t % wet proofing). Dimensions: ( 3 cm x 2.3 cm). Cathode electrode: carbon cloth • coated with a Pt catalyst,(E ‐ TEK, 0.5 mg/cm 2 ). Dimensions : (3 cm x 2.3 cm) Proton exchange system: PEM (Nafion • 117)

Feedstock TS VS moisture pH tCOD (g/g wet (g/g wet (20 o C) (%) (g/g TS) weight) weight) cattle manure 75 0.26 0.12 8.5 0.75 poultry manure 62 0.386 0.34 7.5 0.70 sheep manure 74 0.26 0.23 7.4 0.83 cow manure 88 0.13 0.097 8.7 1.2 pig manure 86 0.14 0.088 7.3 1.02 whey 93 0.07 0.05 6.0 2.2

Feedstock: Mixture ratio Annual production Ratio (%) (tn/year) cattle manure 1792 3.93 poultry manure 15832 34.71 sheep manure 2812 6.17 cow manure 3663 8.03 pig manure 20640 45.25 whey 873 1.91 Total 45612 100 The ratios are similar to those of the study area

Feedstock: Pretreatment Liquid phase: PABR and MFC Filtered Stirring under Waste Dilution in for 30 pressure mixing hot water minutes using a cloth filter Solid Phase A solids/liquid separation step was used as pretreatment, because of the inability of the PABR and the MFC to treat feedstock with high solids levels.

Feedstock: Liquid phase Liquid phase characteristics pH 7.46 TSS (g/L) 5.72 Conductivity (S/cm) 3.93 VSS(g/L) 4.60 TS(g/L) 9.4 VS(g/L) 7.14 Total Carbohydrates (g/L) 1.19 Dissolved Carbohydrates (mg/L) 0.28 Total Kjeldahl Nitrogen (mg/L) 631 Ammonium Nitrogen (mg/L) 378.8 Organic Nitrogen (mg/L) 252.2 Total Phosphorus (mg/L) 120.4 3— P (mg/L) Orthophosphates PO 4 41.5 Organic phosphorus (mg/L) 78.9

PABR Operating Conditions Hydraulic Retention Time 22.3 HRT (d) Switching Period (d) 2 Influent tCOD (g/L) 13.36 Organic Loading Rate 0.6 (g COD /L reactor /d)  Mesophilic conditions (35 o C)  Operation period of 148 days  Gas and liquid samples were taken at regular intervals

Anaerobic co ‐ digestion results (1/2)

Anaerobic co ‐ digestion results (2/2)

Anaerobic co ‐ digestion modeling (1/3)  A simple model developed in Aquasim 2.1 was used to predict the behaviour of the PABR at the HRT of 22.3 d  Basic assumptions o The organic matter is consumed with simple Monod kinetics � � � � ��� · �� � � · � o Yield of methane on the substrate Y meth =6.6901 L meth /L reactor /g COD o Yield of biomass from COD Y x/s =0.05 g CODx /g CODs o Initial dCOD of the four comparments dCOD ini =1.46 g/L o Biomass retention factor R b (to be estimated by the model)  Experimental data (dCOD) of the PABR were used for the estimation of all the kinetic parameters (Saturation factor K s , Maximum specific growth rate μ max , initial biomass concentration ΧΒ ini )

Anaerobic co ‐ digestion modeling (2/3) Fig. 1. dCOD Compartment 1 Fig. 2. dCOD Compartment 2 (experimental-model) (experimental-model) It is clear that the simple Monod kinetics model was able to satisfactorily describe the behavior of the PABR in terms of dCOD, while the values of the estimated parameters are reasonable.

Anaerobic co ‐ digestion modeling (3/3) Fig. 4. dCOD Compartment 4 Fig. 3. dCOD Compartment 3 (experimental-model) (experimental-model) Parameter estimation R b =0.465 μ max =0.0732 d ‐ 1   K s =0.1034 g/L ΧΒ ini =0.126 g/L  

MFC Operating Conditions Constant stirring of the anode and cathode chambers.  Constant temperature at 35 o C and pH=7 (unless stated otherwise).  Continuous aeration of the cathode chamber.  External resistance Rext =1 k Ω .  The anode chamber was operated as a sequence batch reactor (at the end  of each cycle the liquid contents were emptied and the anode chamber was refilled with fresh medium). Anolyte contained:  o Buffer (NaH 2 PO 4 ∙ 2H 2 0, Na 2 HPO 4 ∙ 2H 2 0) o NaHCO3 o KCl o trace elements o glucose as the electron donor Catholyte contained: o Buffer  o KCl

Electricity production with MFC (1/3)  Pretreated and filtered livestock waste and whey as substrate at different initial concentrations (1 st and 2 nd cycle = 0.4 g dCOD/L, 3 rd and 4 th cycle = 0.8 g dCOD/L, 5 th and 6 th cycle = 1.5 g dCOD/L, 7 th cycle = 2.8 g dCOD/L, 8 th cycle = 3.1 g dCOD/L. External resistance R ext = 1k Ω ).  Duration of the cycles increased by increasing the initial concentration of the substrate  dCOD removal efficiency practically constant (67 ‐ 75%).  The MFC could operate at higher wastewater concentrations

Electricity production with MFC (2/3)  Linear relationship between the duration of each cycle operation with the initial concentration according to the equation: y = 92.379 *x.  Low CE (2.1%) of the last cycle (cycle with the highest initial concentration).  Most of the dCOD was removed by methanogens or other non ‐ electrogenic microbes established in the anode rather than by electron transfer bacteria.

Electricity production with MFC (3/3)  Maximum power density remains practically constant (50 mW/m 2 ) for all cycles.  Power generation limited by the high ohmic resistance and not affected by the bacteria or the specific substrates used.  The almost constant slope of the polarization curves confirms the very significant contribution of ohmic losses in the dual chamber MFC.

Conclusions  Two alternative ways for the valorization of livestock manure and whey evaluated  Biogas production rate = 0.13 L/L reactor /d and tCOD removal rate = 79.9%  Relatively high dCOD removal and power density were achieved for the concentrations tested with MFC.  The time needed to degrade the substrate increases linearly with the substrate concentration.  The dCOD removal efficiency and the maximum power density seems not to be affected by wastewater strength.

Thank you for your attention! Thank you for your attention!