Urban tree pruning and agro-industrial residues in composting: application of multivariate analysis (PCA) and Fourier transform infrared spectroscopy (FTIR)

This research aimed to evaluate the efficiency of composting waste from urban and agro-industrial forestry pruning in the broiler production chain (BPC), using PCA multivariate statistics and FTIR spectroscopic analysis. Three composting windrows were assembled, weighing 419 kg (dry matter) with an initial C/N ratio of 22.2. Organic materials such as pruning residues from urban afforestation, cellulosic sausage casing, hatchery residue, floater sludge, and agro-industrial broiler ash composed the windrows. The evaluated treatments were S35: 35 days, S63: 63 days, and S95: 95 days of stabilization. Physicochemical parameters, FTIR, and absorbance index assessed the process. These values were submitted to PCA multivariate statistics to select two PC, capable of explaining 90.2% of the data. PC1 divided the parameters into two groups exhibiting the residues stabilization characteristics at 35, 63, and 95 days of composting. The FTIR displayed an increase in the 1650/2925 and 1650/2845 ratios and a decrease in the 2920/1640 ratio for all treatments as compared to its initial composition. An outcome reflects the degradation of aliphatic groups and increase of aromatic structures as the composting time progresses. The PCA allowed the evaluation of physicochemical parameters and the degree of stabilization of the residues in the composting process. FTIR found significant transformations of the organic matter in the first 35 days of the process.