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The bacterial community assembly patterns and processes are poorly understood in pig manure slurry. We collected pig manure slurry samples during the winter and summer seasons from eight commercial pig farms in South Korea. The V3 region of 16S rRNA genes was PCR amplified and sequenced using paired-end Illumina technology for in-depth characterization of bacterial community. Firmicutes, Bacteroidetes, Proteobacteria, Spirochaetes, and Tenericutes were the predominant bacterial phyla present in slurry samples. Bacterial taxonomic community composition was not influenced by the season; however, phylogenetic community composition was affected by seasonal variations. The community composition and diversity patterns were strongly influenced by pH. The bacterial diversity indices showed a unimodal relationship with pH. Phylogenetic signals were detected over only short phylogenetic distances, revealing that closely related bacterial operational taxonomic units (OTUs) tend to co-occur in the same environment; hence, they are ecologically similar. Across all samples, a niche-based process, through strong environmental filtering imposed by pH, primarily governed bacterial community assembly; however, in samples close to the neutral pH range, the role of environmental filtering was decreased due to neutral community assembly. In summary, pH emerged as the major physico-chemical variable in pig manure slurry that regulates the relative importance of niche-based and neutral processes in shaping the community assembly of bacteria.

The codigestion of slaughter waste with animal manure can improve its methane yield, and digestion parameters; however, limited studies are available for the effectiveness of anaerobic codigestion using swine slaughter waste (SSW) and swine slurry (SS). Hence, this study was conducted to determine the characteristics of SSW and the effect of anaerobic codigestion with (SS) and explored the potential of CH4 production (Mmax), the lag phase period (λ), and effective digestion time (Teff). SSW contains fat and protein contents of 54% and 30% dry weight within 18.2% of solid matters, whereas SS showed only 6% and 28% within 4.1% of solid matters, respectively. During sole anaerobic digestion, SSW produced a high Mmax (711 Nml CH4/g VSadded) but had a long duration λ (~9 days); whereas SS produced a low Mmax (516 Nml CH4/g VSadded) but had a shorter duration λ (1 day). Codigestion increased the Mmax from 22–84% with no significant Teff compared to sole SS digestion. However, the low Mmax of SS and high Mmax of SSW, resulted in a 7–32% decrease in Mmax at codigestion compared to SSW sole digestion. Codigestion improved the digestion efficiency as it reduced λ (3.3–8.5 days shorter) and Teff (6.5–9.1 days faster) compared to SSW sole digestion. The substrate-to-inoculum ratio of 0.5 was better than 1; the volatile solid and micronutrient availability may be attributed to improved digestion. These results can be used for the better management of SSW and SS for bio-energy production on a large scale.