Optimization of alkaline pretreatment of Yagoua rice straw for bioethanol production

The aim of this work is to optimize the alkaline hydrolysis of rice straw lignocellulose using kanwa, with the goal of producing bioethanol. The alkaline pretreatment was carried out using a saline rock from North Cameroon (kanwa) under the following experimental conditions: temperature between 170 and 200°C, and duration between 20 and 60 minutes. Characterization revealed that the local material contained 91.75 ± 0.48% dry matter, 8.25 ± 0.48% water, 31.22 ± 2.04% cellulose, 9.92 ± 2.46% lignin, and 17.72 ± 0.51% hemicellulose. The optimization design (central composite design) used to validate the reducing sugar models was based on the following indicators: Adjusted R² (99.36), AADM (12%), Bf (1.004), and Af (1.049). The optimal pretreatment conditions were 1.681, -1, and 0.808 in terms of temperature, time, and kanwa concentration, resulting in the maximum extraction of 49% cellulose, 2.4% hemicellulose, and 19.3% lignin. A concentration of 4.50 ± 0.02 mg/mL of reducing sugars was obtained under the conditions of 55°C for 72 hours, followed by centrifugation at 4000 rpm for 15 minutes. This resulted in an ethanol yield of 32% and a lower calorific value of 9184 ± 0.01 J/g.