CHARACTERIZING THE BACTERIAL COMMUNITY DURING AEROBIC STABILIZATION OF LIVESTOCK MANURE. WHY SHOULD FEEDSTOCK NOT BE AGED BEFORE COMPOSTING?

The compositions of bacterial communities and populations during aerobic stabilization of livestock manure have been investigated, focusing on how the aging of feedstock affected the bacterial diversity of the composting mass. The livestock manure was divided into two groups - aged and fresh, and then used to prepare the feedstock with additives. Composting experiments were carried out for 15 days using a pilot-scale batch reactor with vacuum-induced aeration. Two different aeration rates were applied to the batch reactor, and their effectiveness was evaluated. Changes in total heterotrophic bacteria count and moisture content were monitored. The associated changes in bacterial community compositions were characterized using 16S ribosomal ribonucleic acid (rRNA) gene sequencing. The Firmicutes in the fresh manure decreased from 48 to 13% for the first ten days, and the dominant phylum shifted to the Proteobacteria (29%), Bacteroidetes (23%), Actinobacteria (20%), and others (15%). Under the given conditions, the use of relatively fresh manure was essential to preserve the diverse bacterial populations in the feedstock and enhance the bacterial diversity during aerobic stabilization. More research should be performed to investigate the degradability of emerging contaminants (e.g., antibiotics) in livestock manure using an engineered composting system providing well-controlled environmental conditions.