STABILIZING FOOD WASTE ANAEROBIC DIGESTION G. Capson-Tojo, M. Rouez, M. Crest, J.-P. Steyer, N. Bernet, J.-P. Delgenès, R. Escudié Lab. for Environmental Biotechnology CIRSEE Paris – France Narbonne – France
What is Food Waste? “Mass of food lost or wasted in the part of food supply chains leading to edible products for human consumption” 1/3 of the food produced worldwide Main contributor of OFMSW FAO (2012), Gustavsson et al. (2011), Melikoglu et al. (2013), UN (2011) 02
What is Food Waste? “Mass of food lost or wasted in the part of food supply chains leading to edible products for human consumption” 1/3 of the food produced Landfjllin Incineratio worldwide g n Main contributor of OFMSW Compostin Anaerobic g digestion (AD) FAO (2012), Gustavsson et al. (2011), Melikoglu et al. (2013), UN (2011) 02
What is Food Waste? “Mass of food lost or EU directive wasted in the part of food (2008/98/CE) supply chains leading to Valorization edible products for human through soil return consumption” mandatory 1/3 of the food produced worldwide Main contributor of OFMSW Compostin Anaerobic g digestion (AD) FAO (2012), Gustavsson et al. (2011), Melikoglu et al. (2013), UN (2011) 02
FW characteristics and AD Common FW characteristics TS VS Countr Carbohydrat Protein Lipid (% (% C/N y es (%) s (%) s (%) w/w) TS) UK 23.7 91.4 41.4 15.1 23.5 13.9 Italy 27.5 86.6 ~ 56.4 16.1 17.5 18.3 21.0 90.3 61.8 19.8 12.1 16.1 Several studies with FW as substrate for methane and/or hydrogen production Biochemical methane potentials (BMPs): 300-600 ml CH 4 ·g VS -1 Banks et al. (2012), Capson-Tojo et al. (2017a), VALORGAS (2010) 03
FW characteristics and AD Common FW characteristics TS VS Countr Carbohydrat Protein Lipid (% (% C/N SUITABLE y es (%) s (%) s (%) w/w) TS) HOWEVER SUBSTRAT 23.7 91.4 41.4 15.1 23.5 13.9 27.5 86.6 ~ 56.4 16.1 … 17.5 18.3 E 21.0 90.3 61.8 19.8 12.1 16.1 Several studies with FW as substrate for methane and/or hydrogen production Biochemical methane potentials (BMPs): 300-600 ml CH 4 ·g VS -1 Banks et al. (2012), Capson-Tojo et al. (2017a), VALORGAS (2010) 03
Challenges in FW AD Fast degradation High protein content Main challenge in batch Main challenge in long- reactors: initial term operation: accumulation of VFAs accumulation of NH 3 and and acidifjcation inhibition Organic matter Organic nitrogen VFAs NH 3 Inhibition methanogenic archaea VFA accumulation pH drop 04
Stabilizing FW AD Mono-digestion Unstable operation (“inhibited steady state”) Failure even at low OLRs Addition of water as industrial solution: environmental and economical constraints Supplementation of trace elements (TEs) Banks et al. (2012), Capson-Tojo et al. (2016), Nagao et al. (2012), Qiang et al. (2012) 05
TEs and FW TEs in Commercial FW used Required for the synthesis of enzymes Concentration Compound (mg·kg TS -1 ) Fe 1,114 Co non-detected Cu 11.2 Mn 27.6 Mo 1.26 Zn 38.4 Improved methane production rates and Ni 1.19 VFA degradation Se ? kinetics Lack of TEs? Higher OLRs achieved Banks et al. (2008, 2011), Capson-Tojo et al. (2017b), Yirong (2016), Zhang et al. (2017) 06
Objectives: comparison stabilization options Avoid initial VFA peak: compare 3 strategies for stabilizing FW AD Co-digestion Working at low Addition of with paper temperatures trace waste (PW) (30 ° C) elements C/N, inhibitors dilution, (TEs) bufgering capacity, Enzyme synthesis VS. VS. NH 3 + NH 4 + slower biodegradation H + Consecutive batch reactor at increasing substrate loads process applicable at industrial scale simulation a plug-fmow reactor with digestate recirculation 07
Material and Methods Research strategy Four mixed pilot reactors Working volumes 7.5-20 l Mesophilic operation (37 ° C) Commercial FW from GN fast food restaurant supermarket fruit & vegatable fruit & vegatable restaurant supermarket distributor 08
Material and Methods Research strategy Four mixed pilot reactors Working volumes 7.5-20 l Mesophilic operation (37 ° C) Commercial FW from GN Concentration Specifjc conditions Compound reactor (mg·l -1 ) Control: fed with FW Fe 100 T30: temperature of 30 ° C Co 1.0 Cu 0.1 Co-PW: fed with FW and PW Mn 1.0 (3:1 w/w) Mo 5.0 Sup- TEs: doped with TEs Zn 0.2 Ni 5.0 Se 0.2 08
Material and Methods Research strategy Four mixed pilot reactors Working volumes 7.5-20 l Mesophilic operation (37 ° C) Commercial FW from GN Specifjc conditions Feeding strategy Control: fed with FW 1 st load: 0.087 kg FW·kg inoculum -1 (S/X 0.25 g VS·g VS -1 ) T30: temperature of 30 ° C 2 nd load: 0.173 kg FW·kg inoculum -1 Co-PW: fed with FW and PW (3:1 w/w) 3 rd load: 0.260 kg FW·kg inoculum -1 Sup- TEs: doped with TEs Twice each load Reactors fed if biogas plateau or 500 ml CH 4 ·g VS -1 reached 08
l C H c e c o n Control ( m N ; T A 0.173 Contro 0.087 i c a c i d 0.173 0.173 e y i e l d l 0.087 0.173 Continuous accumulation of i o n propionic acid a n e t h P r o p Gradual decrease 600 12 of methane M 10 400 8 production rate & 6 200 4 longer lag phase 2 0 0 0 20 40 60 80 100 120 140 160 09
l C H c e c o n Control VS. T30 ( m N ; T A c o n c e n t r a t i o n ( g · l - 1 ) 0.173 Contro 4 · g V S - 1 ) 0.087 i c a c i d 0.173 0.173 e y i e l d l 0.087 0.173 Continuous accumulation of i o n propionic acid a n l C H e t h P r o p Gradual decrease 600 12 of methane e t h a n e y i e l d ( m M 10 400 8 production rate & 6 200 4 longer lag phase 2 0 0 P r o p i o n i c a c i d ; T A N 0 20 40 60 80 100 120 140 160 T3 0.087 0.087 0.173 0 0.173 T30: slower kinetics and longer lag phase built-up of 600 12 M 10 propionic acid 400 8 6 200 4 2 0 0 0 20 40 60 80 100 120 140 160 180 Time (d) 10
l C H c e c o n Control VS. Co-PW ( m N ; T A c o n c e n t r a t i o n ( g · l - 1 ) 0.173 Contro 0.087 4 · g V S - 1 ) i c a c i d 0.173 0.173 e y i e l d l 0.087 0.173 Continuous accumulation of i o n propionic acid a n l C H e t h P r o p Gradual decrease 600 12 of methane M e t h a n e y i e l d ( m 10 400 8 production rate & 6 200 4 longer lag phase 2 0 0 P r o p i o n i c a c i d ; T A N 0 20 40 60 80 100 120 140 160 Co- PW 0.087 Co-PW: lower 0.087 yields 0.173 0.173 0.173 Higher accumulation of 600 25 M 20 propionic acid 400 15 (over 20 g ∙ l -1 ) 10 200 5 0 0 0 20 40 60 80 100 120 140 160 180 (NH 3 + NH 4 + ) Time (d) Methane Yield Propionate T AN 11
l C H c e c o n Control VS. Sup-TEs ( m N ; T A 0.173 Contro 0.087 i c a c i d 0.173 0.173 e y i e l d l 0.087 0.173 Continuous accumulation of i o n propionic acid a n e t h P r o p Gradual decrease 600 12 of methane M 10 400 8 production rate & 6 200 4 longer lag phase 2 0 0 0 20 40 60 80 100 120 140 160 Sup- 0.1730.173 TEs Sup- TEs: faster kinetics but still 0.260 propionic acid Inhibition at 0.260 kg 0.260 FW·kg inoculum -1 (NH 3 + NH 4 + ) Methane Yield Propionate TAN 12
Conclusions Propionic acid accumulation => key issue for FW AD Acidifjcation at high loads Low temperature and co-digestion with PW: discarded TEs addition: improved kinetics and higher substrate loads (but still propionic acid accumulation) Operational implications Batch mode might not be the best option Methane production cannot be used as sole criteria for reactor feeding Research challenges Favor consumption of: propionic acid and/or HAc and/or H 2 13
Thank you for your kind attention LBE, INRA (France) http://www1.montpellier.inra.fr/narbonne/ renaud.escudie@inra.fr
To t a l p r o d u c t s ( g C O D ) C H 4 y ie l d ( m l· g V S - 1 ) 1 st batch: GAC and TEs Similar methane yields and COD conversions 500 Lag phases in 20 400 methane 15 300 production 10 200 + GAC P r o p io n ic a c id ( g ∙ l- 1 ) 5 100 A c e tic a c id ( g ∙ l- 1 ) Shorter lags 0 0 0 10 20 30 0 10 20 30 Time (d) Time (d) Stability up! Improvement due to favored HAc 18 consumption 16 4 14 12 3 Propionic acid 10 8 consumption not 2 6 improved... 4 1 2 0 0 0 10 20 30 0 10 20 30 Time (d) Time (d) 33
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