Abstract
A haloalkaline anaerobic microbial community obtained from soda lake sediments was used to inoculate anaerobic reactors for the production of methane rich biogas. The microalga Spirulina was successfully digested by the haloalkaline microbial consortium at alkaline conditions (pH 10, 2.0 M Na+). Continuous biogas production was observed and the obtained biogas was rich in methane, up to 96%. Alkaline medium acted as a CO2 scrubber which resulted in low amounts of CO2 and no traces of H2S in the produced biogas. A hydraulic retention time (HRT) of 15 days and 0.25 g Spirulina L−1 day−1 organic loading rate (OLR) were identified as the optimal operational parameters. Metagenomic and metatranscriptomic analysis showed that the hydrolysis of the supplied substrate was mainly carried out by Bacteroidetes of the “ML635J-40 aquatic group” while the hydrogenotrophic pathway was the main producer of methane in a methanogenic community dominated by Methanocalculus.
Highlights
Extremophilic microorganisms are bacteria and archaea which inhabit, thrive in and colonize environments characterized by extremely harsh conditions (Berlemont and Gerday, 2011; Gupta et al, 2014)
In the work presented here we show that it is possible to use a haloalkaline anaerobic microbial community for the anaerobic digestion of the microalgae Spirulina at alkaline conditions, and that the obtained biogas is rich in methane
In this work we have shown that it is possible to use a haloalkaline anaerobic microbial community for the production of biogas
Summary
Extremophilic microorganisms are bacteria and archaea which inhabit, thrive in and colonize environments characterized by extremely harsh conditions (Berlemont and Gerday, 2011; Gupta et al, 2014). The carbonate system, CO2/HCO−3 /CO23−/OH−, shifts toward the formation of bicarbonate, CO23−, the CO2 released during the decomposition of organic matter (OM) would remain trapped in solution as (bi)carbonate resulting in biogas composed mainly of methane. This methane rich biogas could directly be used as biomethane for vehicles or for the national gas grid (Persson et al, 2006; Weiland, 2010)
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