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In order to strengthen the bio-based economy, it is necessary to produce value-added products by processing all fractions of the biomass, especially lignin. Isolation of lignin at atmospheric pressure and lower temperature will make it possible to recover lignin and use it for different purposes. In the present study, lignins were recovered from wood sawdust by applying six different organosolv treatments at atmospheric pressure. The lignins (ethanol organosolv lignin (EOL), alkaline glycerol organosolv lignin (AGOL), acetic acid organosolv lignin (AAOL), formic acid/acetic acid/water organosolv lignin (FAWOL 1 (40/40/20, v/v/v), FAWOL 2 (50/30/20, v/v/v), FAWOL 3 (30/50/20, v/v/v)) were compared in terms of yield, thermal properties, weight-average molecular weight, and fast pyrolysis properties. The effect of isolation method on lignin yield and structure was remarkable. Organosolv treatments at atmospheric conditions resulted in precipitation yields between 6.6% (ethanol organosolv) and 42% (alkaline glycerol organosolv). The lignin precipitated with the highest yield (AGOL) actually had the highest ash content (3.9%) and the lignin precipitated with the lowest yield (EOL) had the lowest ash content (1.2%). According to FTIR analysis, all lignins exhibited peaks at similar wavelengths but with different intensities. The weight-average molecular weight of lignins ranged between 1373 g/mol (AGOL) and 7400 g/mol (FAWOL 1). The polydispersity index of lignins ranged between 7.3 (FAWOL 1) and 2.5 (EOL and AAOL), where the lignins isolated from formic acid/acetic acid/water liquors showed higher polydispersity index compared to other lignins. Pyrolysis gas chromatography/mass spectrometry (Py-GC/MS) revealed that pyrolysis product distribution was strongly affected from the isolation method. The most abundant phenolic compound, which was observed in all lignins, was 2-methoxy-4-methylphenol (4-methylguaiacol), which was followed by 2-methoxy-4- (2-propenyl) phenol (eugenol) and guaiacol, respectively. It has been observed that each lignin is a good candidate for a different end-use due to their own characteristics.

In the present study, various lignocellulosic biowastes (wood sawdust, olive pomace, walnut shell, apricot seed, tea stalk, hazelnut husk) were hydrothermally carbonized at 220 °C for 90 min. Since the hydrochars have several end-uses, this study particularly investigates their end-use as solid fuels and precursors of activated carbon after chemical activation. Activated hydrochars were obtained from the hydrochars of wood sawdust, olive pomace, walnut shell, apricot seed, tea stalk, hazelnut husk by chemical activation with KOH at 600 °C. As fuels, all hydrochars had higher fixed carbon content, lower volatile matter content and higher ignition temperatures compared to their original biomass samples. Olive pomace hydrochar, which has high heating value (25.56 MJ/kg) and low ash content (5.5%), has the best fuel properties among hydrochars investigated. Activated hydrochars demonstrated BET surface areas of 308.9–666.7 m2/g (activated hydrochar of wood sawdust and tea stalk), and total pore volumes of 0.25–0.73 cm3/g (activated hydrochar of olive pomace and wood sawdust). The average pore size distribution of the activated hydrochars ranged between 1.05 nm (olive pomace)- 4.74 nm (wood sawdust). All agricultural-based activated hydrochars had similar average pore size distribution of 1.05–1.25 nm, which fell in the range of super-microporous structure. With the average pore size of 4.74 nm, activated hydrochar of wood sawdust could be classified under mesoporous structure. This study clearly points out that biomass type definitely affected fuel properties of hydrochars and the porous structure of the activated hydrochars.

Pyrolysis of olive pomace and copyrolysis of olive pomace with RDF blends were investigated by TGA. To see the effect of heating rate on pyrolysis behavior and kinetic parameters of olive pomace, TG and DTG curves were obtained at three different heating rates (10, 20, and 30°C min−1) between 20°C and 800°C. The results showed that activation energy decreased as the heating rate was increased. In the pyrolysis profile of olive pomace, weight loss was observed almost in one stage where two peaks overlapped between temperatures 170–372°C, having a highest peak at 342°C. In the case of olive pomace-RDF blends, copyrolysis experiments were conducted under N2 atmosphere at a heating rate of 10°C min−1 from 20°C to 800°C. The pyrolysis profile of the blends presented three peaks (except moisture removal) meaning three consecutive reactions: cellulose-hemicellulose decomposition, plastics decomposition and CaCO3 decomposition. Lignin decomposition comprised all the stages. Because of its high activation energy, using olive pomace alone in the pyrolysis reaction required a high temperature operation or long reaction time in the reactor. Blending it with RDF decreased the activation energy, decreased the peak temperatures, increased the number of pyrolysis stages (decomposition of plastics and inorganic carbonate based additives), and increased the time required for higher conversion rates. RDF which had a high ash content and low calorific value was found as more useful as a fuel when it was blended with olive pomace. Lower activation energies observed in the relevant decomposition stages indicated that the reaction became faster upon blending. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 649–656, 2014