Sustainability Indicators of Four Biomass Pretreatment Methods for the Energy Transition in Colombia

Objective: To compare pretreatment methods for lignocellulosic biomass, focusing on the feasibility of using renewable energy through electric-powered techniques. Theoretical Framework: The energy transition is expected to generate surplus green electricity. This surplus can enable sustainable small-scale lignocellulose pretreatments. Methods: We compared two conventional pretreatments, steam explosion (SE) and ammonia fiber expansion (AFEX), with two electric-powered pretreatments, reactive extrusion (RE) and ball milling mechanocatalysis (Me). Feasibility was assessed using these indicators: normalized total value added (TVA), safety, health, and environmental (SHE) impacts, and energy efficiency (carbohydrate yield to energy consumption ratio), based on literature data. A cumulative index (CI) combined TVA with SHE impacts, emphasizing that high economic value alone is insufficient if the pretreatment negatively affects safety, health, or the environment. Results and Discussion: Economic viability varied; SE and AFEX performed best (TVA range: SE: 0.04 to 0.54; AFEX: 0.08 to 0.21). RE exhibited potential despite energy efficiency challenges, unlike Me (TVA: RE: -2 to 0.01; Me: -28 to -8). When considering CIs that combine TVA with SHE impacts, RE was competitive with AFEX (CI: RE: 1.3-2.9; AFEX: 1.7-1.9; SE: 0.7-1.2; Me: 8.9-28.9). Energy efficiency showed gains for all methods (Me: 0.02-0.18; RE: 0.38-3.94; SE: 1.22-3.59; AFEX: 1.33-3.92 kWh/kg). RE overlaps with SE and AFEX indicating potential. Research Implications: The data suggest feasible scenarios for integrating renewable energy into biomass pretreatments, enabling small-scale energy utilization. Originality/Value: The analysis explores diverse energy uses to enhance sustainability, by presenting practical possibilities for community involvement for a fair and equitable energy transition.