Optimum operating conditions for brewerʹs spent grain soda pulping

The soda pulping of brewerʹs spent grain (BSG) pretreated with dilute-acid was studied. A first-order full-factorial design was used to evaluate the effect of the operational variables: soda concentration (1–2%), temperature (80–120 °C) and pulping time (30–90 min), on the properties of the pulp (cellulose and lignin contents) obtained from BSG. The factorial design permitted to identify the optimum operating conditions for BSG soda pulping. Equations relating the responses (properties of the pulp) to the operational variables were thus proposed, and fitted the experimental results at 99 and 90% confidence levels, for the cellulose and lignin contents, respectively. The best pulping conditions (2% soda concentration, 120 °C, 90 min) led to a pulp containing 72.1% w/w cellulose and low residual lignin content (10.4% w/w).