Pyrolysis of Lignocellulosic Waste from Second-Generation Ethanol Industry

Interest on the use of lignocellulosic waste from second-generation (2G) ethanol industry has increased each year, where biochar and bio-oil production by pyrolysis is a relevant alternative. Biochar has high energy, adsorption capacity and soil enrichment potential, while bio-oil has applications for the pharmaceutical, chemical and fuel industries. Nonetheless, research on pyrolysis of this residue has not been reported, nor has the characterization of the bio-oil produced been profiled. Besides this, few studies on biochar and bio-oil produced from sugarcane bagasse have analyzed the effects of temperature and heating rate on yield. This work investigates the production and characterization of biochar and bio-oil by pyrolysis from this 2G waste. Temperature (500–700 °C) and heating rate (5–15 °C min−1) were the variables evaluated using a full factorial design (FFD), while biochar and bio-oil yields were the responses investigated. Characterization was carried out by thermogravimetric analysis, physical and chemical analyses, Fourier transform infrared spectroscopy, dispersive energy X-ray fluorescence spectroscopy (EDS) and gas chromatography–mass spectrometry (GC–MS). From FFD results, linear models were successfully fit to the responses. Maximum biochar and bio-oil yields of 40.3% and 39.0% were found for a set of temperature-heating rates of 500 °C-5 °C min−1 and 700 °C-15 °C min−1, respectively, in agreement with residue from first-generation ethanol process. The biochar presented low content of ash, volatile materials and moisture as well as high fixed carbon content and heating values, showing high energy potential. The bio-oil exhibited alternativity as source of phenols (53.2%) for industry based on the GC–MS results.