Abstract
This study investigates the environmental footprint and functional efficacy of upcycling spent coffee grounds (SCG) as a bioactive ingredient in bio-based topical emulsions. Utilizing an eco-friendly ultrasound-assisted extraction (UAE) method with a green ethanol-water solvent, we retrieved a polyphenol-rich fraction from SCG, primarily characterized by chlorogenic acid and caffeine. This extract was incorporated at varying concentrations (0.5%, 1.0%, and 2.0% w/w) into a bio-based oil-in-water (O/W) emulsion formulated with alkyl polyglucoside emulsifiers. In vitro assays demonstrated robust antioxidant performance, with the 2.0% SCG emulsion exhibiting free-radical scavenging activity (DPPH and ABTS assays) comparable to synthetic butylhydroxytoluene (BHT). Emulsion stability testing over 30 days under accelerated aging conditions (40°C) confirmed excellent physical and chemical integrity, preserving over 85% of its initial antioxidant capacity. Concurrently, a cradle-to-gate Life Cycle Assessment (LCA) was conducted to evaluate the environmental impacts of the upcycled formulation against a conventional synthetic antioxidant-based counterpart. The LCA revealed a 32% reduction in Global Warming Potential (GWP) and a 25% reduction in Cumulative Energy Demand (CED) for the SCG-based emulsion, chiefly driven by waste diversion and the avoidance of petrochemical-based synthetic inputs. These findings highlight that upcycled SCG can serve as a highly effective, circular, and environmentally superior active ingredient in sustainable cosmetic and skincare formulations.
