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Rumen Content and anaerobic sludge co-inoculated of in Cellulose FED anaerobic batch digesters
Municipal solid waste is a very complex and heterogeneous system made of a wide range of materials. Among thesematerials, more than 50% are biodegradable and can be valorized through treatments based on anaerobic biologicalprocesses to produce biogas, a renewable source of energy. The ligno-cellulosic fraction of waste, mainly constituted by paper and cardboard (25%), plays an essential role in the production of biogas and is responsible for almost 80% ofbiogas emission (Eleazer, et al., 1997).
Further Authors:
T. Serain - Irstea, France
It is consequently a keystone in the anaerobic biological processes ofdegradation. However, cellulose is a recalcitrant molecule, and is not hydrolyzed easily in bioprocesses, which limits itsanaerobic digestion kinetic (Verstraete, et al., 1996) and efficiency. The rate of biodegradation occurring in animaldigestive systems, such as ruminants’ guts, is significantly higher despite much lower residence times than in digesters(Weimer, et al., 2009). Consequently, to improve the cellulose degradation and methane production in anaerobicdigesters, several studies involving rumen microorganisms in anaerobic digesters have been conducted (Gijzen, et al.,1987, Blasig, et al., 1992, Barnes & Keller, 2003). However, macroscopic observations suggest that ruminal flora maynot settle easily in industrial anaerobic processes (O'Sullivan & Burrell, 2007). The potential of cellulolytic ruminalflora properties expression in an anaerobic digester can therefore be questioned.In this study, cellulose degrading anaerobic batch incubations were set up and run in parallel. They were co-inoculatedwith MSW digester sludge and ruminal content. 13C labeled cellulose degradation and reaction pathways were followedand described over time with GC-C-IRMS. These results were linked to the identification and the monitoring of thedynamic (Automated Ribosomal Intergenic Spacer Analysis method, ARISA (Fisher & Triplett, 1999)) ofmicroorganisms.This experiment highlighted the functional characteristics of cellulose degradation digestion in a digester co-inoculatedwith a natural and an industrial biomass. After 65 days, 50% of the cellulose was converted into biogas, composed of60% of methane. The dominant intermediates were acetate and propionate. Their partial 13C enrichment suggests astrong degradation of endogenous substrates. The dynamics of functional groups followed by ARISA showed a strongcorrelation of the appearance and disappearance of bands with the dynamics of Volatile Fatty Acids. However none ofthe groups found in the reactors were initially present in the rumen. Cellulolytic potentiality of ruminal flora did notexpressed during the experiment despite inoculation in large quantities, in a closed system, with a suitable substrate(cellulose) and favorable physico-chemical conditions such as mesophilic temperature or the presence of rumen fluid.Yet the diversity was more important in the batch reactor than in the initial industrial sludge. The co-inoculationprobably disordered diversity equilibrium within the anaerobic industrial sludge, and several ecological niches weretaken over by species subdominant in the initial inocula. Co-inoculation of an exogenous flora with anaerobic sludgecould thus be an environmental lever to modify diversity in full scale reactors.This study demonstrates that a more precise identification of selection pressures that lead to the stabilization of differenttypes of flora is necessary to use natural flora into industrial systems. Design of processes mimicking animals digestivesystems also seems very promising (Godon, et al., 2010, Bayané & Guiot, 2011).Statement This work was realized in the Framework of the DANAC research project (ANR-Bioénergies 2009)
| Copyright: | © European Compost Network ECN e.V. | |
| Quelle: | Orbit 2012 (Juni 2012) | |
| Seiten: | 7 | |
| Preis inkl. MwSt.: | € 7,00 | |
| Autor: | Olivier Chapleur  Théodore Bouchez Ariane Bize Laurent Mazeas | |
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