Anaerobic digestion of microalgal biomass in lab-scale digesters for the production of volatile fatty acids

Transcription

1 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 th 2014, Philadelphia, PA, USA

2 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

3 Microalgal biomass Unicellular. High diversity: 100k described, 800k estimated. Great at fixating CO 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

4 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

5 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), Frigon J.-C., AD of microalgal biomass for VFA production, May 13 th 2014

6 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

7 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

8 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 Screening microagae strains for their productivity in methane following anaerobic digestion. Applied Energy, 108: 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): Frigon J.-C., AD of microalgal biomass for VFA production, May 13 th 2014

9 Culture of Scenedesmus 300 L Brite-BoxTM PBR; Growth rate 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 Frigon J.-C., AD of microalgal biomass for VFA production, May 13th 2014

10 Anaerobic digesters 10 Frigon J.-C., AD of microalgal biomass for VFA production, May 13th 2014

11 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: % 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

12 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) R35-sCOD R55-sCOD R35-VFA R55-VFA Weeks of operation 12 Frigon J.-C., AD of microalgal biomass for VFA production, May 13 th 2014

13 Results Parameters Units Digester 35 C Digester 55 C Hydrolysis g scod/ gtvs 0.38 ± ± 0.03 Acidification % VFA/ scod 45 ± 3 47 ± 4 VFA mg/l 6461 ± ± 180 Butyrate Iso-butyrate Yield mg/l 2249 ± ± 88 mg/l 723 ± ± 6 mg COD / g TVS in 171 ± 5 95 ± 5 Q H 2 ml / g TVS in % 80% 50% 13 Frigon J.-C., AD of microalgal biomass for VFA production, May 13 th 2014

14 LCFA Residual LCFA 55 > 35 C 14 Frigon J.-C., AD of microalgal biomass for VFA production, May 13 th 2014

15 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 Microalgae production costs. Aquafuels. Gao et al Algae biodiesel. A feasibility report. 15 Frigon J.-C., AD of microalgal biomass for VFA production, May 13 th 2014

16 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

17 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 : jean-claude.frigon@cnrc-nrc.gc.ca 17 Frigon J.-C., CNRC, RV pratique sur la DA, 29 janvier 2014