Two-step valorization of invasive species Rosa rubiginosa L. husk waste through eco-friendly optimized pectin extraction and subsequent pyrolysis

Abstract

This research studied chemical and thermal treatments of rosehip husk (RH), from invasive species in Patagonia Rosa rubiginosa, which is considered a main waste in the seed-oil extraction industry, to obtain added-value products by optimizing an eco-friendly pectin extraction, followed by pyrolysis of the remaining solid (RHW). The aim was to valorize the rosehip husk of an invasive species by finding the optimal conditions for pectin extraction (maximum yield and minimum CO2 emissions) and assessing the pyrolysis process together with the products obtained, finding the temperature of maximum production of each species in the gaseous product. By applying multi-objective optimization, it was found that the optimal yield was 17.83 % with 456.7 g of CO2 emitted for kg of pectin at temperature T = 79.6 ºC, time t = 30 min, and pH = 2.3. By TGA, 6 processes were identified in the pyrolysis of RHW: moisture evaporation and 5 consecutive reactions which were related to lignocellulosic biomass components decomposition. The kinetic parameters of each reaction were obtained by isoconversional method (activation energy), compensation effect method (pre-exponential factor), and master-plots method (conversion function). The pyrolysis gaseous products of energetic interest identified were CH4, H2, and C2H4, with maximum production at 630, 700, 850 ºC respectively. The main compounds found by GC-MS were diacetone alcohol, mesityl oxide, butylated hydroxytoluene, among others. The ash was analyzed by XRD and showed a high Ca concentration (46.9 %) with presence of Ca(OH)2, MgO, KCaPO4, and K4Ca(PO4)2.