Wax is an organic compound found on the surface of lignocellulose biomass to protect plants from physical and biological stresses in nature. With its small mass fraction in biomass, wax has been neglected from inclusion in the design of the biorefinery process. This study investigated the interfering effect of wax in three types of lignocellulosic biomass, including rice straw (RS), Napier grass (NG), and sugarcane bagasse (SB). In this study, although small fractions of wax were extracted from RS, NG, and SB at 0.57%, 0.61%, and 1.69%, respectively, dewaxing causes changes in the plant compositions and their functional groups and promotes dissociations of lignocellulose fibrils. Additionally, dewaxing of biomass samples increased reducing sugar by 1.17-, 1.04-, and 1.35-fold in RS, NG, and SB, respectively. The ethanol yield increased by 1.11-, 1.05-, and 1.23-fold after wax removal from RS, NG, and SB, respectively. The chemical composition profiles of the waxes obtained from RS, NG, and SB showed FAME, alcohol, and alkane as the major groups. According to the conversion rate of the dewaxing process and ethanol fermentation, the wax outputs of RS, NG, and SB are 5.64, 17.00, and 6.00 kg/ton, respectively. The current gasoline price is around USD 0.903 per liter, making ethanol more expensive than gasoline. Therefore, in order to reduce the cost of ethanol in the biorefinery industry, other valuable products (such as wax) should be considered for commercialization. The cost of natural wax ranges from USD 2 to 22 per kilogram, depending on the source of the extracted wax. The wax yields obtained from RS, SB, and NG have the potential to increase profits in the biorefining process and could provide an opportunity for application in a wider range of downstream industries than just biofuels.
Pretreatment with pure, mixed, and diluted deep eutectic solvents (DESs) was evaluated for its effect on Napier grass through compositional and characterization studies. The morphological changes of biomass caused by pretreatment were analyzed by FTIR and XRD. The cellulose and hemicellulose content after pretreatment using mixed DES increased and decreased 1.29- and 4.25-fold, respectively, when compared to untreated Napier grass. The crystallinity index (CrI. %) of mixed DES sample increased due to the maximum removal of hemicellulose (76 %) and delignification of 62 %. The material costs of ChCl/FA and ChCl/LA for a single run are ≈2.16 USD and ≈1.65 USD, respectively. Pure DES showed that ChCl/LA pretreatment enhanced delignification efficiency and that ChCl/FA increased hemicellulose removal. It was estimated that a single run using ChCl/LA:ChCl/FA to achieve maximum hemicellulose and lignin removal would cost approximately ≈1.89 USD. Future work will evaluate the effect of DES mixture on enzyme digestibility and ethanol production from Napier grass. HYPOTHESES: Deep eutectic solvent (DES) pretreatment studies on the fractionation of lignocellulosic biomass have grown exponentially. The use of pure and diluted DES has been reported to improve saccharification efficiency, delignification, and cellulose retention (Gundupalli et al., 2022). These studies have reported maximum lignin removal but also a lower effect on hemicellulose removal from lignocellulosic biomass. It was hypothesized that mixing two pure DESs could result in maximum removal of hemicellulose and lignin after pretreatment. To our knowledge, no studies have been performed to investigate the efficiency of pretreatment using a DES mixture and compared the outcome with pure and diluted DESs. Furthermore, it was hypothesized that using two pure DESs in a mixed form could lower the material cost for each experimental run. Process efficiency was determined by compositional, XRD, and FTIR analysis. Avenues for future research include determining glucose and ethanol yields during the enzymatic saccharification and fermentation processes.