Optimizing dilute sulfuric acid thermohydrolysis of dried food waste using the desirability function to produce a fermentation-friendly hydrolysate for biohydrogen production

Abstract

This study optimized dilute sulfuric acid thermo-hydrolysis of dried food waste (FW). Key hydrolysis factors were systematically varied, such as acid concentration, solution-to-solid ratio, oil solidifier addition, agitation, temperature, and reaction time. Multi-objective optimization was employed to maximize reducing sugar yield while minimizing the formation of inhibitory compounds, 5-hydroxymethylfurfural (HMF) and furfural, in the hydrolysate. A two-step optimization approach was used: screening experiments to identify active factors and numerical optimization of a desirability function in Design-Expert 13.0 to find optimal factor configurations in order to achieve the desired objective values. The optimal factor configurations (1.53 % H₂SO₄, 6 mL H₂SO₄/g dried FW, 1.49 g oil solidifier, 0 rpm, 80 °C, 60 min) achieved a composite desirability value of 0.80, yielding hydrolysate with 35.43 g/L reducing sugars, 0.14 g/L HMF, and 0.55 g/L furfural, with prediction errors below 10 %. The hydrolysate also had proteins (2.65 g/L), NaCl (0.30 g/L), and metals (Mg, Zn, Fe, Cu, Mn, Mo, Ni, Co) in beneficial amounts, while Cr and Cd remained within safe levels. These findings advance FW valorization by producing a fermentation-friendly hydrolysate for sustainable biohydrogen generation.