Potential of acetic acid to restore methane production in anaerobic reactors critically intoxicated by ammonia as evidenced by metabolic and microbial monitoring.
Lemaigre, Sébastien; Gerin, Patrick A; Adam, Gilleset al.
2023 • In Biotechnology for biofuels and bioproducts, 16 (1), p. 188
Anaerobic digestion; Free ammonia nitrogen intoxication; Microbial community monitoring; Process recovery; Restoration strategy; Ammonia-nitrogen; Anaerobic digestion process; CH 4; Free ammonia; Methanogenesis; Microbial communities; Restoration strategies; Biotechnology; Renewable Energy, Sustainability and the Environment; Applied Microbiology and Biotechnology; Energy (miscellaneous); Management, Monitoring, Policy and Law
Abstract :
[en] [en] BACKGROUND: Biogas and biomethane production from the on-farm anaerobic digestion (AD) of animal manure and agri-food wastes could play a key role in transforming Europe's energy system by mitigating its dependence on fossil fuels and tackling the climate crisis. Although ammonia is essential for microbial growth, it inhibits the AD process if present in high concentrations, especially under its free form, thus leading to economic losses. In this study, which includes both metabolic and microbial monitoring, we tested a strategy to restore substrate conversion to methane in AD reactors facing critical free ammonia intoxication.
RESULTS: The AD process of three mesophilic semi-continuous 100L reactors critically intoxicated by free ammonia (> 3.5 g_N L-1; inhibited hydrolysis and heterotrophic acetogenesis; interrupted methanogenesis) was restored by applying a strategy that included reducing pH using acetic acid, washing out total ammonia with water, re-inoculation with active microbial flora and progressively re-introducing sugar beet pulp as a feed substrate. After 5 weeks, two reactors restarted to hydrolyse the pulp and produced CH4 from the methylotrophic methanogenesis pathway. The acetoclastic pathway remained inhibited due to the transient dominance of a strictly methylotrophic methanogen (Candidatus Methanoplasma genus) to the detriment of Methanosarcina. Concomitantly, the third reactor, in which Methanosarcina remained dominant, produced CH4 from the acetoclastic pathway but faced hydrolysis inhibition. After 11 weeks, the hydrolysis, the acetoclastic pathway and possibly the hydrogenotrophic pathway were functional in all reactors. The methylotrophic pathway was no longer favoured. Although syntrophic propionate oxidation remained suboptimal, the final pulp to CH4 conversion ratio (0.41 ± 0.10 LN_CH4 g_VS-1) was analogous to the pulp biochemical methane potential (0.38 ± 0.03 LN_CH4 g_VS-1).
CONCLUSIONS: Despite an extreme free ammonia intoxication, the proposed process recovery strategy allowed CH4 production to be restored in three intoxicated reactors within 8 weeks, a period during which re-inoculation appeared to be crucial to sustain the process. Introducing acetic acid allowed substantial CH4 production during the recovery period. Furthermore, the initial pH reduction promoted ammonium capture in the slurry, which could allow the field application of the effluents produced by full-scale digesters recovering from ammonia intoxication.
Research center :
LIST - Luxembourg Institute of Science & Technology
Disciplines :
Biotechnology
Author, co-author :
Lemaigre, Sébastien; Environmental Research and Innovation Department, Luxembourg Institute of Science and Technology, Rue du Brill 41, L-4422, Belvaux, Luxembourg. sebastien.lemaigre@list.lu
Gerin, Patrick A; Earth and Life Institute, Bioengineering, Université Catholique de Louvain, Croix du Sud 2, Box L7.05.19, B-1348, Louvain-la-Neuve, Belgium
Adam, Gilles; Environmental Research and Innovation Department, Luxembourg Institute of Science and Technology, Rue du Brill 41, L-4422, Belvaux, Luxembourg
Klimek, Dominika; Environmental Research and Innovation Department, Luxembourg Institute of Science and Technology, Rue du Brill 41, L-4422, Belvaux, Luxembourg
Goux, Xavier; Environmental Research and Innovation Department, Luxembourg Institute of Science and Technology, Rue du Brill 41, L-4422, Belvaux, Luxembourg
HEROLD, Malte ; University of Luxembourg ; Environmental Research and Innovation Department, Luxembourg Institute of Science and Technology, Rue du Brill 41, L-4422, Belvaux, Luxembourg
Frkova, Zuzana; Environmental Research and Innovation Department, Luxembourg Institute of Science and Technology, Rue du Brill 41, L-4422, Belvaux, Luxembourg
CALUSINSKA, Magdalena ; University of Luxembourg ; Environmental Research and Innovation Department, Luxembourg Institute of Science and Technology, Rue du Brill 41, L-4422, Belvaux, Luxembourg
Potential of acetic acid to restore methane production in anaerobic reactors critically intoxicated by ammonia as evidenced by metabolic and microbial monitoring.
Influence of the reactor design on the dynamics of the microbial populations involved in the biomethanation process
Funders :
FNR - Fonds National de la Recherche
Funding number :
CO11/SR/1280949
Funding text :
This work was supported by the Fonds National de la Recherche, Luxembourg (FNR CORE 2011 project GASPOP, CO11/SR/1280949: Influence of the Reactor Design and the Operational Parameters on the Dynamics of the Microbial Consortia Involved in the Biomethanation Process) and by LIST core funding.
Commentary :
This research aims at optimizing the anaerobic digestion process, a nature-based process that convert all components of organic matter (lipids, proteins, carbohydrates), except lignin, into methane (energy vector) and eco-friendly fertilizers. Yet the process is biological in nature and complex, and is thus prone to deficiencies. The paper treats of one of the two most common process failures, alkalosis, and proposes a process recovery strategy suitable for on-farm application.
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