Compostagem de lodo de curtume com poda de árvore, maravalha e cinza de caldeira em duas condições de relação C/N inicial

Abstract

Large amounts of solid waste are generated in the tannery industries throughout Brazil, including sludge generated before the tanning step. The sludge generated before the tanning step has a high organic load and can be harmful to the environment if it is disposed incorrectly. Its use in agriculture is a common practice, however, some undesirable effects point to the need for prior treatment. Composting can be used to treat this residue. However, few studies that use this technique to treat tannery sludge. The C/N ratio is a parameter that must be taken into account when assembling the wires, and it is recommended to have approximately 30: 1 at the beginning of the process. However, this relationship may be impracticable, since the waste considered as a source of nitrogen are the biggest challenges of the industries and generated in greater quantity. In this sense, the objective of this work was to evaluate the efficiency of different initial C/N ratios in the treatment of the sludge generated before the tanning stage, through composting, using as pruning the tree pruning and shaving, in the presence and absence of the boiler ash. Sixteen rows were assembled, with initial C/N ratio calculated from 16: 1 and 12: 1. The volume was 288 liters for the ashless litter and 318 liters for the ash litter in its composition. During 60 days parameters such as pH, temperature, electrical conductivity, carbon percentage, nitrogen percentage, C/N ratio, material aspect and mass and volume reduction were monitored. The pH of all treatments was alkaline at the end of the composting, which indicates the possibility of using the compost to correct the soil pH. Only the treatment T5 reached a temperature higher than 55ºC during the thermophilic phase, indicating a possible sanitization of the residues. The treatments with tree pruning were more efficient in reducing the C/N ratio, especially T5 and T6 with 41.52 and 42.02% reduction, respectively. On the other hand, the treatments with wood shavings did not exceed 5.43% reduction of the C/N ratio. All treatments underwent volume and mass reduction, with emphasis on T5 and T6. There was greater decharacterization of the residues with tree pruning in its composition. Therefore, the compounds T5 and T6 stood out, evidencing that the best C/N ratio to start the process is 16:1, and the carbon source is tree pruning.