Microbial community dynamics and process performance of a full-scale two-stage anaerobic digester under the replacement from energy crop to poultry manure

BACKGROUND: This study assessed the composition and dynamics of the bacterial and archaeal communities in a full-scale two-stage anaerobic digester over five months. The plant was fed on a variable mixture of feedstock, in which the energy crops were replaced with poultry manure/litter (from 1.6% to 7.5%) to reduce the operational costs. RESULTS: The elevated concentration of ammonia in the digester did not hamper biogas production and its concentration of methane. The low level of acetate, butyrate and propionate in the methanogenesis phase indicated a strong activity of acetotrophic methanogens. PCR-DGGE and sequencing have demonstrated that the stability of the volatile fatty acid distribution concurred with low level of population shifts as shown by the moving windows analysis. Nevertheless, PCoA analyses revealed that the variation in the digester alimentation and the carbon:nitrogen (C:N) ratio had a key role in assembly the bacterial and archaeal communities. The high ammonia level favoured the growth of Caldicoprobacteraceae and Syntrophomonadaceae, whereas dominant archaea detected belonged to the family of Methanosarcinaceae. CONCLUSION: Cheap and readily available N-rich feedstock could be used safely to decrease the costs of the anaerobic digestion process.