Synthesis of 5-Hydroxymethylfurfural (HMF) from Agro-Industrial Grape Residues: An Integrated Chemical and Enzymatic Catalysis Approach with Life Cycle Assessment

5-Hydroxymethylfurfural (HMF) classifies as one of the 12 main molecules derived from biomass, it being a versatile platform for synthesizing a wide range of chemicals. The present study combines experiments with life cycle analysis (LCA) to assess the scalability and sustainability of the valorization of white grape pomace (WGP) to HMF through the evaluation of the pretreatment, enzymatic hydrolysis, and catalytic dehydration steps. The selected pretreatment was a 1 h cycle at 55 °C WGP solid−liquid extraction, whereby glucose and fructose extraction yields of 299.34 and 318.90 mg g −1 dry WGP were attained, respectively. In the hydrolysis stage, the highest glucose yields were achieved at 50 °C and pH 5, with a value of 175.9 mg g −1 WGP at a commercial enzyme (Cellic CTec3) preparation of 150 g L −1 . Catalytic dehydration obtained similar HMF (%) yields of 10.9 and 11.2 for the soluble sugar fractions from the pretreatment and hydrolysis of WGP, respectively. However, the conversion of fructose in the pretreatment fraction was 60% higher than the conversion obtained in the hydrolysate fraction. The LCA results revealed that process efficiency is crucial in assessing environmental sustainability with a clear inverse correlation found between process yield and global warming potential (GWP). For a realistic scenario with conversion set at 72%, the GWP values obtained for the recovery of the pretreated fraction and the hydrolysate were approximately 2.03 kg CO 2 e kg −1 FU. These values demonstrate a significant environmental benefit when compared to the equivalent no-valorization scenario (disposal of WGP), which generates a burden of approximately 4.0 kg CO 2 e kg −1 FU equivalent. Thus, the recovery of WGP for HMF synthesis is a highly viable and sustainable strategy at the local level.