Anaerobic digestion of microalgal biomass in lab-scale digesters for the production of volatile fatty acids Jean-Claude Frigon, Marvin Gruhn and Serge R. Guiot 11 th World Congress on Industrial Biotechnology. May 12-15 th 2014, Philadelphia, PA, USA
Plan Introduction Rationale for the project Methodology Culture of Scenedesmus sp.-amdd Digesters Results Operational parameters VFA production Other parameters Techno-economic aspects Concluding remarks 2 Frigon J.-C., AD of microalgal biomass for VFA production, May 13 th 2014
Microalgal biomass Unicellular. High diversity: 100k described, 800k estimated. Great at fixating CO 2. 15 000 novel organic compounds chemically determined. Applications: biofuels (jet fuel, biodiesel, biomethane, biohydrogen, bioethanol); GHG mitigation by CO 2 sequestration; Depollution (N and P from wastewater); Food, animal feed, pharmaceutical, cosmetics, nutraceutical. 3 Frigon J.-C., AD of microalgal biomass for VFA production, May 13 th 2014
Anaerobic digestion: general statements Microbiological conversion of organic material in the absence of oxygen, that results in the production of biogas (renewable energy - biofuel) and digestate (fertilizer); AD is a proven and reliable technology (35+ years, thousands installations); AD implementation first as a cleanup / treatment process; For the past 10 years, emphasis on AD as a biofuel production process. 4 Frigon J.-C., AD of microalgal biomass for VFA production, May 13 th 2014
Feedstocks for AD SSO, food wastes, FVW; Sludge (municipal, pulp and paper); Manure (bovine, pig, chicken); FOG, slaughterhouse wastes, glycerol; Crops (corn, beets, switchgrass); Microalgal biomass. Recent focus; Valid option: 14.0 MJ/kg vs biodiesel (6.6), ethanol (1.8). Harun et al. (2011).Technoeconomic analysis of an integrated microalgae photobioreactor, biodiesel and biogas production facility. Biomass and Bioenergy, 35 (1), 741 747. 5 Frigon J.-C., AD of microalgal biomass for VFA production, May 13 th 2014
AD pathway Conventional pathway conversion of organics to methane, CO 2. This study we stop at acidogenesis Accumulation of C2-C4 carboxylic acids, lactate, alcohols. 6 Frigon J.-C., AD of microalgal biomass for VFA production, May 13 th 2014
Rationale for the project Why are we doing this? To explore other alternatives to biofuel production from microalgal biomass Biofuel alone is often not enough to sustain a viable project; AD can offer more than biofuels: carboxylic acids; Acetic, propionic and butyric acids with a commercial value. Part of a biorefinery approach Tap CO 2 from an emitter; Grow biomass in wastewater (free N and P); Generate added value with a bioproduct; Produce some renewable energy; Closed-loop. Effluent recirculation upstream. 7 Frigon J.-C., AD of microalgal biomass for VFA production, May 13 th 2014
Scenedesmus sp.-amdd Why this strain? High AD potential: top 3 from a screening of > 20 strains; Experience with larger-scale growth in wastewater. High yield. Jean-Claude Frigon, Frédérique Matteau-Lebrun, Rekia Ganda Bachir, Patrick J. McGinn, Stephen O'Leary and Serge R. Guiot. 2013. Screening microagae strains for their productivity in methane following anaerobic digestion. Applied Energy, 108:100-107. McGinn PJ, Dickinson KE, Bhatti S, Frigon JC, Guiot SG, O Leary SJB. Integration of microalgae cultivation with industrial waste remediation for biofuel and bioenergy production: opportunities and limitations. Photosynth Res 2011;109(1 3):231 47. 8 Frigon J.-C., AD of microalgal biomass for VFA production, May 13 th 2014
Culture of Scenedesmus 300 L Brite-BoxTM PBR; Growth rate 0.3-0.4 d-1; Continuous operation; Algal cell density 7-10 X 106; CO2 on demand; ph 7.0; T : 25 C. Szumski R., A. Patrzykat. Value proposition alternatives for the industrial cultivation of microalgae in Canada. 3rd International Conference on Algal Biomass, Biofuels and Bioproducts, Toronto, CAN, June 2013. 9 Frigon J.-C., AD of microalgal biomass for VFA production, May 13th 2014
Anaerobic digesters 10 Frigon J.-C., AD of microalgal biomass for VFA production, May 13th 2014
Operational parameters of the digesters Parameters Values Inoculum Bovine manure ph 4.4 ± 0.1 OLR 2.5 ± 0.1 gtvs/l.d HRT 15 d T C 35 / 55 Arrhenius equation: reaction rate increase with temperature. Algae paste: 20 30 % solids 45% carbohydrates; 44% proteins; 4% lipids 11 Frigon J.-C., AD of microalgal biomass for VFA production, May 13 th 2014 J.D. Cronk, CHEM 420 Bioanalytical chemistry, 2010
Hydrolysis and VFA production 22 weeks of operation. Hydrolysis level: 55 > 35 C? VFA concentration: 35 > 55 C Soluble COD and VFA from effluent (mg/ L) 20000 15000 10000 5000 R35-sCOD R55-sCOD R35-VFA R55-VFA 0 0 5 10 15 20 25 Weeks of operation 12 Frigon J.-C., AD of microalgal biomass for VFA production, May 13 th 2014
Results Parameters Units Digester 35 C Digester 55 C Hydrolysis g scod/ gtvs 0.38 ± 0.02 0.43 ± 0.03 Acidification % VFA/ scod 45 ± 3 47 ± 4 VFA mg/l 6461 ± 278 3575 ± 180 Butyrate Iso-butyrate Yield mg/l 2249 ± 113 1630 ± 88 mg/l 723 ± 33 45 ± 6 mg COD / g TVS in 171 ± 5 95 ± 5 Q H 2 ml / g TVS in 0 20 25% 80% 50% 13 Frigon J.-C., AD of microalgal biomass for VFA production, May 13 th 2014
LCFA Residual LCFA 55 > 35 C 14 Frigon J.-C., AD of microalgal biomass for VFA production, May 13 th 2014
Techno-economic aspects Yield for 35 C digester: value of the produced VFA VFA yield: presume all butyric acid: 155 gba/ kg biomass (dry weight); Price for industrial grade BA: $1200/ ton ($400- $3000); $190 / ton dw as a value; $470 - $8100 / ton dw, for growing the biomass. Yield for 35 C digester: value of methane Natural gas: $2-3/GJ $10 / GJ for RNG; 348 L STP/ kg dw 13.3 GJ / ton dw $133 / ton dw. F.G. Acien. 2010. Microalgae production costs. Aquafuels. Gao et al. 2009. Algae biodiesel. A feasibility report. 15 Frigon J.-C., AD of microalgal biomass for VFA production, May 13 th 2014
Concluding remarks VFA production from microalgal biomass is possible: Best yield at 35 C 25% hydrolysis; improvement needed 155 g VFA / kg microalgal biomass Projection at large scale not yet viable. Future prospects: Increase VFA yield from biomass Reduce production cost of microalgal biomass Higher value of VFA as a product (market for bio-acids ). 16 Frigon J.-C., AD of microalgal biomass for VFA production, May 13 th 2014
Bioenergy Program at NRC Increasing the efficiency of primary biomass conversion technologies; Optimizing processes for biofuel upgrading; Resolving biofuel-power plant compatibility issues; Lowering capital and operating costs for bioenergy systems and components. Thank you Jean-Claude Frigon, M.Sc. Program Technical Leader Bioenergy Program Energy, Mining and Environment Tel : 514-496-6369 jean-claude.frigon@cnrc-nrc.gc.ca www.cnrc-nrc.gc.ca 17 Frigon J.-C., CNRC, RV pratique sur la DA, 29 janvier 2014