Effect of cold alkaline extraction in obtaining hemicelluloses and cellulose from high-yield forest species (Ulmus minor)

Abstract In recent years, interest in obtaining high value‑added compounds and bioenergy from fast‑growing energy and industrial crops has increased significantly. Accordingly, this study evaluates an integrated biorefinery scheme based on Cold Alkaline Extraction (CAE) and alkaline delignification applied to one of these crops ( Ulmus minor ). Using a central composite experimental design, the optimal conditions for CAE were determined (100 g L −1 , 40 °C, and 60 min). This process yields a solid fraction rich in cellulose and a liquid fraction rich in hemicelluloses. The solid fraction is subjected to an alkaline delignification process, the temperature ranges from 155 to 175 °C, the alkali concentration from 14 to 22%, and a fixed time of 60 min. This approach allows evaluating the impact of CAE and delignification conditions on the chemical and physical–mechanical properties of cellulosic pulps. This improvement is reflected in substantially lower Kappa numbers (40.4), higher viscosities (532.5 cm 3 g⁻ 1 ), and significantly increased mechanical indices–burst, tear, and tensile strengths of 1.34 MPa·m 2 kg⁻ 1 , 7.41 N m 2 g⁻ 1 , and 30.1 N m g⁻ 1 , respectively. Moreover, the liquid fraction obtained after CAE, enriched in hemicelluloses, showed a high potential for the production of xylose and furfural through controlled acid hydrolysis, reaching furfural concentrations of up to 2.24 g L −1 under optimal conditions. The results validate the initial hypothesis and consolidate the CAE + alkaline delignification scheme as an effective strategy for the simultaneous production of high value‑added compounds and high‑quality cellulosic pulps.