*2.2. Biomass Characterization*

The HHV was determined using a Parr oxygen bomb calorimeter (model 1261, Modline, IL, USA) on densified GG samples (1.0 g, 6 mm diameter using a Carver laboratory press (Wabash, IN, USA) at 68 MPa) according to ASTM D5865-04. The ash content, volatile matter (VM), and fixed carbon (FC) for GG were evaluated based on proximate analysis (ASTM E870-82). The elemental analysis was conducted on a Costech ESC 4010 elemental analyzer (Valencia, CA, USA) to obtain the C and N contents.

The GG sample (4.0 g) was submitted to Soxhlet extraction using CH2Cl2 (150 mL) for 16 h, and the extractives content was determined gravimetrically, according to ASTM D1108-96. The CH2Cl2 extract was analyzed for lipid profiles as their fatty acid methyl ester (FAME) derivatives after acidic methanolysis (2 mL of CH3OH/H2SO4/CHCl3 (1.7:0.3:2.0 *v*/*v*/*v*) at 90 ◦C for 90 min) and subsequent gas chromatography-mass spectrometry analysis (Thermoscientific ISQ-Trace1300 (Madison, WI, USA); Phenomenex (Torrance, CA, USA) ZB5 30 m x 0.25 mm column; 40 ◦C (1 min) to 280 ◦C at 5 ◦C/min) [22]. The extractive-free GG (200 mg) was subsequently analyzed for lignin and carbohydrate contents by acid hydrolysis [72% H2SO4 (2 mL), 60 min, 30 ◦C], followed by secondary hydrolysis [4% H2SO4, 30 min, 121 ◦C] in an autoclave, according to ASTM D 1106-96. The Klason lignin content was evaluated gravimetrically after filtration. Acid soluble lignin was determined at 205 nm of the filtered hydrolysate (250 mL), using an extinction coefficient of 110 L g−<sup>1</sup> cm−<sup>1</sup> (Genesys 50, ThermoScientific, Hanover Park, IL, USA). The hydrolysis

filtrate (5 mL) was subjected to carbohydrate analysis according to ASTM E 1758-01. The monosaccharides were quantified by HPLC (two Rezex RPM columns, 7.8 mm × 300 mm, Phenomenex, Torrance, CA, USA) at 85◦C on elution with water (0.5 mL min−1) using differential refractive index detection (Waters model 2414, Milford, MA, USA). All analyses were performed in duplicate.

FTIR spectroscopy was conducted on an iS5 spectrometer (ThermoNicolet, Madison, WI, USA) in the single bounce attenuated total reflection (ATR) mode (iD5, ZnSe). The determination of the lignin syringyl/guaiacyl (S/G) ratio was conducted at the relative band intensities at 1462 and 1508 cm<sup>−</sup>1. The relative band intensities at 1370 and 2900 cm−<sup>1</sup> were used in determining cellulose crystallinity as the total crystalline index (TCI). [7]. The cellulose lateral order index (LOI) was determined from band intensity ratios at 1430 and 897 cm−<sup>1</sup> [35]. XRD was carried out on a Siemens D5000 diffractometer (Karlsruhe, Germany) (2θ from 5 to 50◦ with steps of 0.2◦). The diffractogram was peak fitted using Origin software prior to determination of the cellulose crystallinity index (CCI = (1 − (Iam/I002)), where Iam is the intensity of the peak at 2θ = 15◦ and I002 is the maximum intensity of the (002) plane diffraction at 2θ = 22◦) [22].

#### *2.3. Thermogravimetric Analysis (TGA)*

The GG sample with an initial mass of 5.44 ± 0.25 mg was subjected to dynamic heating experiments in a Perkin Elmer TGA-7 (Waltham, MA, USA) instrument in either an N2 or dry air environment at a flow rate of 30 mL/min. The heating temperature was raised from ambient conditions (29.15 ± 0.64 ◦C) to 900 ◦C at three heating rates (5, 10, and 20 ◦C/min), and the data obtained were analyzed using the Pyris v11 software. The experiments were performed in duplicate.
