Effectiveness of incorporation of crude glycerin as a source of labile carbon in the composting of poultry production residues

Abstract Due to the surplus of crude glycerin generated in biodiesel production, its use as a carbon source in the composting of poultry chain residues is a promising alternative. Composting besides promoting the stabilization of these residues generates an organic compost that can be used in the production of seedlings. Therefore, the purpose of this study was to evaluate the addition of crude glycerin extracted from biodiesel production as a source of labile carbon in the composting of poultry manure, and to evaluate the quality of the organic compound generated. The experiment was assembled and conducted in windrows built from wooden pallets. The variables monitored in the composting process were temperature, pH and electrical conductivity. At the beginning and end of the composting process, the volume, mass, total organic carbon, total Kjeldahl nitrogen, total phosphorus, potassium, cellulose, hemicellulose, lignin and germination index were evaluated. As a microbiological parameter, basal respiration was evaluated. All treatments reached thermophilic phase temperatures; however, T4 treatment (6% crude glycerin) remained above 55 °C for a longer time (33 days). The mass and volume reduction ranged from 26.62 to 42.39 and 26.85 to 42.72%, respectively. The final C: N ratio values were approximately 12: 1. In general, the organic compounds obtained had good agronomic characteristics without the presence of phytotoxic agents, demonstrating that the addition of 6% of crude glycerin does not affect the quality of the final compound.