Biochemical Methane Potential of Swine Slaughter Waste, Swine Slurry, and Its Codigestion Effect

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.