Slaughterhouse waste (SW) poses significant environmental challenges due to its complex composition, but anaerobic digestion offers a way to recover valuable biogas from SW. This study investigated the anaerobic co-digestion of beef cattle slaughterhouse waste (BCSW) with either cattle feces (CF) or swine slurry (SS). The biomethane potential, maximum methane yield (M_max), lag phase duration, and effective digestion time (T_eff) for the individual substrates and the combinations were analyzed. BCSW alone exhibited M_max of 578.5 Nml CH₄/g VS_added with a lag phase of 11 days, while CF and SS alone exhibited M_max of 397.2 and 289.8 Nml CH₄/g VS_added, respectively. Co-digestion of BCSW and SS resulted in M_max increase of 48–75.5%, with negligible effects on T_eff compared to solitary SS digestion. Similarly, co-digestion of BCSW and CF increased M_max by 6.2–40.4%, with no significant impact on T_eff compared to solitary CF digestion. However, both co-digestions led to a reduction in M_max (12.1–27%) when compared to BCSW digestion alone. Co-digestion with SS shortened the lag phase duration by 2.8–7.8 days and accelerated T_eff by 5.8–8.3 days due to SS’s high concentrations of essential micronutrients like cobalt and nickel which aid digestion. This study concluded that co-digestion of BCSW with SS is an effective strategy for enhancing methane production and digestion efficiency, offering a viable approach for proper disposal of BCSW while improving biogas output.

Waste activated sludge (WAS), a byproduct of livestock wastewater treatment, poses significant disposal challenges due to its low biodegradability and potential environmental impact. Anaerobic digestion (AD) offers a sustainable approach for methane recovery and sludge stabilization. This study evaluates the biomethane potential (BMP) of WAS and its co-digestion with swine slurry (SS), water lily (Nymphaea spp.), and lotus (Nelumbo nucifera) shoot biomass to enhance methane yield. Batch BMP assays were conducted at substrate-to-inoculum (S/I) ratios of 1.0 and 0.5, with methane production kinetics analyzed using the modified Gompertz model. Mono-digestion of WAS yielded 259.35–460.88 NmL CH₄/g VS_added, while co-digestion with SS, water lily, and lotus increased yields by 14.89%, 10.97%, and 16.89%, respectively, surpassing 500 NmL CH₄/g VS_added. All co-digestion combinations exhibited synergistic effects (α > 1), enhancing methane production beyond individual substrate contributions. Lower S/I ratios improved methane yields and biodegradability, highlighting the role of inoculum availability. Co-digestion reduced the lag phase limitations of WAS and plant biomass, improving process efficiency. These findings demonstrate that co-digesting WAS with nutrient-rich co-substrates optimizes biogas production, supporting sustainable sludge management and renewable energy recovery in livestock wastewater treatment systems.