Figure 6. Overall biomass pretreatment mass balance of WT sorghum stover by pretreatment (140°C for 3h) and enzymatic hydrolysis (20 FPU/g of biomass, 72h) using (a) ChCl-DHBA-W DES and (b) ChCl-DHBA-EG DES, and TG sorghum stover using (c) ChCl-DHBA-W DES and (d) ChCl-DHBA-EG DES.
Compared to the binary DES, both ternary DESs (ChCl-DHBA-W and ChCl-DHBA-EG) resulted in higher fermentable sugar production. For a better understanding of the overall mass balance of both approaches with WT and TG sorghum stover, process flow diagrams with the mass balance of major biomass components were presented in Figure 6 . The mass balance was calculated based on 100 g of sorghum stover as the starting material. The average value of each treatment was used for the mass balance calculation. Stream 1 describes the amount of major biomass components in the untreated feedstock (i.e., sorghum stover), and Stream 4 shows the final products (fermentable sugars after enzymatic hydrolysis). As shown in Figure 6 , both WT and TG sorghum stovers have over 25 g of extractives with ~9 g of ash, and the three main components (glucan, xylan, and lignin) accounted for approximately 65 g per 100 g biomass. WT biomass had slightly higher glucan and lignin content than TG biomass, with the TG biomass having more extractives. Among four scenarios, water-incorporated DHBA DES exhibited higher glucose production (26.0 g and 26.9 g with the pretreated WT and TG biomass) than ethylene glycol-incorporated one (25.0 g and 26.0 g with the pretreated WT and TG biomass). However, ethylene glycol-incorporated DHBA DES resulted in higher xylose production (5.2 g and 5.1 g with the pretreated WT and TG biomass) was higher than water one (3.1 g and 3.7 g with the pretreated WT and TG biomass) even though its xylan conversion was lower (Figure 3 ). This is because ChCl-DHBA-EG pretreated biomass retained more xylan during the pretreatment (Table 2) . For this reason, ChCl-DHBA-EG pretreated sorghum stover produced the highest amount (31.1 g) of the total fermentable sugars (glucose + xylose) with the pretreated TG biomass, shown in Figure 6d . However, a large portion of the hemicellulose was solubilized in the liquid fraction during the pretreatment; therefore, the separation and utilization of these sugars after the recovery of lignin and DES should be considered to complete the biorefinery strategy.