Abstract
This study investigates the effects of NaOH pretreatment on the microstructural
distribution and biomethane released from Xyris capensis. Xyris capensis was pretreated
with NaOH using 1, 2, 3, 4, and 5% w/w concentrations for 60, 45, 30, 20, and 15 min
of exposure time, respectively, at a 90 ◦C autoclave temperature. The impacts of the
pretreatment technique on microstructural arrangement, crystallinity, and functional groups
were examined with a scanning electron microscope (SEM), X-ray diffraction, and Fourier
transform infrared (FTIR), respectively. NaOH-pretreated and untreated feedstocks were
digested at the laboratory scale at a mesophilic temperature (37 ± 2 ◦C) for 35 days for their
biomethane potential. It was discovered from the SEM analysis that NaOH pretreatment
affects the microstructural arrangement of Xyris capensis, and the sample with the longer
exposure time is the most affected. The results of XRD and FTIR also indicated that NaOH
pretreatment lowered the crystallinity of the feedstock and significantly influenced the
functional groups at varying degrees. Biomethane yield was recorded to be 258.68, 287.80,
304.02, 328.20, 310.20, and 135.06 mL CH4/gVSadded, representing 91.53, 113.09, 125.10,
143.00, and 129.68% more increases than the untreated feedstock. It was discovered that
the optimum biomethane generation was achieved when 4% w/w of NaOH concentration
was utilized for 20 min. This study shows that a higher NaOH concentration with a shorter
retention time is more suitable for Xyris capensis. This pretreatment method can improve
the biomethane yield of Xyris capensis and can be investigated for industrial applications
and its use on other lignocellulose feedstocks, especially energy grasses.
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