Project description:Mitigation of N2O-emissions from soils is needed to reduce climate forcing by food production. Inoculating soils with N2O-reducing bacteria would be effective, but costly and impractical as a standalone operation. Here we demonstrate that digestates obtained after biogas production may provide a low-cost and widely applicable solution. Firstly, we show that indigenous N2O-reducing bacteria in digestates grow to high levels during anaerobic enrichment under N2O. Gas kinetics and meta-omic analysis show that the N2O respiring organisms, recovered as metagenome-assembled genomes (MAGs) grow by harvesting fermentation intermediates of the methanogenic consortium. Three digestate-derived denitrifying bacteria were obtained through isolation, one of which matched the recovered MAG of a dominant Dechloromonas-affiliated N2O reducer. While the identified N2O-reducers encoded genes required for a full denitrification pathway and could thus both produce and sequester N2O, their regulatory traits predicted that they act as N2O-sinks in the current system. Secondly, moving towards practical application, we show that these isolates grow by aerobic respiration in digestates, and that fertilization with these enriched digestates reduces N2O emissions. This shows that the ongoing implementation of biogas production in agriculture opens a new avenue for cheap and effective reduction of N2O emissions from food production.
Project description:Metagenome data from soil samples were collected at 0 to 10cm deep from 2 avocado orchards in Channybearup, Western Australia, in 2024. Amplicon sequence variant (ASV) tables were constructed based on the DADA2 pipeline with default parameters.
Project description:Anaerobic digestion (AD) is a core technology in management of urban organic wastes, converting a fraction of the organic carbon to methane and the residual digestate, the biorest, have a great potential to become a major organic fertilizer for agricultural soils in the future. At the same time, mitigation of N2O-emissions from the agricultural soils is needed to reduce the climate forcing by food production. Our goal was therefore to enrich for N2O reducing bacteria in AD digestates prior to fertilization, and in this way provide an avenue for large-scale and low-cost cultivation of strongly N2O reducing bacteria which can be directly introduced to agricultural soils in large enough volumes to alter the fate of nitrogen in the soils. Gas kinetics and meta-omics (metagenomics and metaproteomics) analyses of the N2O enriched digestates identified populations of N2O respiring organisms that grew by harvesting fermentation intermediates of the methanogenic consortium.
