Experimental and Technoeconomic Assessment of Monosaccharide and Furan Production under High Biomass Loading without Solid–Liquid Separation

Excessive water and chemicals are often used in biomass valorization because of postpretreatment washing and wastewater treatment. To address this issue, three pretreatment scenarios (I: H₂SO₄ pretreatment with NaOH neutralization; II: NaOH pretreatment with H₂SO₄ neutralization; and III: parallel H₂SO₄ and NaOH pretreatments following their integration) with enzymatic hydrolysis were performed for glucose, xylose, 5-hydroxymethylfurfural (HMF), and furfural production at high solid (15 and 25%, w/v) loading without solid–liquid separation and further detoxification. With an initial solid loading of 25% (w/v), scenario I reached the highest furfural (4.94 g/L) and HMF (2.82 g/L) concentrations, scenario II achieved the highest glucose (73.25%) and xylose (77.49%) yields, while scenario III displayed the highest sugar concentration (74.53 g/L). Only the hydrolysate from NaOH pretreatment and enzymatic hydrolysis with 10% initial solid loading can be efficiently fermented to ethanol (17.92 g/L) by the traditional yeast. Technoeconomic analysis showed that hydrolase unit cost ($2.00–10.00/kg) notably governs the capital investment and annual operating cost. The lower annual glucose [197.28 thousand metric tons (TMt)] and xylose (52.11 TMt) output with sugar revenue of $255.05 million for scenario I was compensated by HMF (6.98 TMt) and furfural (10.31 TMt) output with furan revenue of $80.11 million. Scenario II had the higher annual glucose (208.46 TMt) and xylose (71.19 TMt) output than scenario III (glucose: 206.04 TMt; xylose: 65.32 TMt), but its total revenue ($286.01 million) was notably lower than scenario III ($330.71 million). This indicates that furans play a critical role in determining the potential value of the hydrolysate. A sugar minimum selling price of $2013.23/Mt was achieved by scenario III with the hydrolase unit cost of $4.00/kg. Sensitivity analyses revealed that the hydrolase unit cost was a dominating factor determining the sugar minimum selling price.