Resíduos da indústria ervateira: caracterização e produção de briquetes e compósitos

Abstract

This study aimed to evaluate the chemical characterization of mate tea residues, evaluating the properties of your extract, then making briquettes and plastic-wood composites. To do so, samples of two yerbamate residues, with and without bark, were ground in Willey type mil and classified into vibratory sieves, giving rise to the 40/60mesh fraction, which was used to quantify the contents of ash, total extractives, Klason lignin, holocellulose, alpha-cellulose, hemicellulose, condensed tannins, total phenolics and antioxidant activity, all analyses were performed in triplicate. For the manufacture of briquettes, laboratory briquettes machine were used, using 50g fraction for each briquette, which were heated to 110ºC and pressed for 5min under pressure of 100bar, with cooling time of 10 minutes. Analysis of apparent and energetic density, upper, lower and useful calorific value, thermogravimetric analysis (TGA) and also fixed carbon and volatile materials were performed. For the manufacture of composites, two concentrations of sawdust (40/60mesh) were used more high density polyethylene (HDPE) 75/25% and 50/50% respectively and also a third with 100% HDPE (control). Of these, physical properties (moisture content, dimensional stability, hygroscopicity) were analyzed, and mechanical (Janka hardness) followed by scanning electron microscopy (SEM). The results of the chemical analysis for mate tea residues, with bark (EM1) and without bark (EM2), presented ash contents (3.78 and 3.56%), total extractives (20.38 and 18.53%), Klason lignin content (16.37 and 16.24%), holocellulose (64.35 and 66.56%) and alpha-cellulose (30.76 and 31.42%) respectively. For characterization of EM1 and EM1 extract, was obtained: phenolic compounds (1,409 and 1,067 mgGAE/g), antioxidant activity (93,5 and 93,1 % inhibition) and condensed tannins (0,059 and 0,028 mgCE/g) respectively. In the briquettes, apparent density values were obtained from 1540.29 to 1560.68 Kg/m³, energetic density from 6110.67 to 6191.56 Mcal/m³, static resistance 800 to 1253 Kgf. For combustion analyses, we have superior calorific (residues with and without bark) with 4622 and 4635 Kcal/kg, lower with 4251 and 4264 Kcal/kg, and useful with 3967 and 3963 Kcal/kg, respectively. In volatile materials, the percentage for EM1 waste was 75.85 and 77.38% for EM2 and fixed carbon with 20.36% for EM1 and 19.05% for EM2. Thermogravimetric analysis showed that mass losses began at 51ºC and, and thermal degradation began at 270 to 275ºC, with maximum peak at 380 to 385ºC. Composites obtained an average moisture content (TU) of 1.5%, indicating that when the homogenization of the residue plus HDPE was performed, the moisture content reduced about 4.5%, taking into account the TU of the residues (6%). The dimensional stability (ASE), water absorption (AA), water absorption rate (TAA) and Janka hardness were satisfactory in both concentrations of residue plus HDPE, however, better results were found in composites containing 75% of HDPE. In the same way as the results for the previous variables, the SEM micrographs showed that from the addition of a greater amount of HDPE (75%), there is greater homogenization of the pieces, attributed to the fact that in the homogenization and pressing process there is a high heating of the particles, thus forming more uniform surfaces and more regular interiors. In general, from the results obtained in this study, it can be concluded that EM1 and EM2 mate tea waste have a high potential for new technologies and can be used both in the manufacture of plasticwood composites and in energy generation through briquetting.