Comparison of the efficiency of inoculants in the anaerobic digestion of cattle, swine and turkey waste for methane production

Economic activities based on the production of animal protein require waste management to ensure economic growth and sustainability of the sector. Anaerobic digestion (AD) is a way of valorizing this residue, reducing greenhouse gas emissions and the environmental impact related to animal production. The search for processes that increase biogas generation is constant, and the study of inocula in AD is promising as an innovation strategy. The objective of this study was to analyze the efficiency of adding commercial (B) and allochthonous granular (S) inoculants in the AD of cattle manure (C), swine deep litter (M) and turkey litter (T). The following residue concentrations were evaluated: 1 = 8.5 gVS.L⁻¹; 2 = 17 gVS.L⁻¹; 3 = 25.5 gVS.L⁻¹. The commercial inoculum was effective in the conversion of swine manure (M2B – 401 mLCH4.g⁻¹COD_add). For turkey litter, the test with both inoculums stood out (T3BS – 312 mLCH₄.gCOD⁻¹_add). The AD of cattle manure with the addition of both inocula (C2BS) improved degradability, with COD removal of 78%. However, for this residue, there was high methane production without the addition of inoculum (484 mLCH4.gCOD⁻¹_add). Butyric acid was completely consumed in the cattle manure and turkey litter tests (T3BS), leaving the hydrogenotrophic pathway predominant. In M2B there was partial consumption of acetic and propionic acid, which suggests the occurrence of acetoclastic and hydrogenotrophic pathways. Biological treatment with the addition of commercial and granular inoculants showed positive results in improving methane production, especially in lignocellulosic residues, such as swine deep litter and turkey litter.