Sustainable base oils from non-edible fats: performance of esterified, epoxidized, and hydroxylated brown grease

Brown grease (BG), a high free-fatty-acid rendering coproduct, was upgraded to lubricant base stocks <i>via</i> one of four single-step functionalization methods: ethyl esterification, methyl esterification, epoxidation, or hydroxylation to give FAEEc/b, FAMEc/b, Epoxy BGc/b, or Hydro BGc/b, respectively (from crude, c, or bleached, b, BG). Each modification was carried out on crude and degummed/bleached brown grease, and the ten materials were evaluated by thermogravimetric analysis (<i>T</i> _d,5%), dynamic (<i>µ</i>) and kinematic (<i>ν</i>) viscosities at 40 and 100 °C, density, viscosity index (VI), and pour point, then mapped to ISO VG grades. Clear structure-property trends emerge. Esterification lowers <i>ν</i> ₄₀ and improves temperature-thinning (FAEEb: <i>ν</i> ₄₀ = 9.33 mm² s^-1, VI = 199, pour point = 0 °C; ISO VG 10). Hydroxylation raises <i>ν</i> ₄₀ into mid-grade ranges (Hydro BGc: <i>ν</i> ₄₀ = 98.4 mm² s^-1, <i>ν</i> ₁₀₀ = 12.5 mm² s^-1, VI = 121; ISO VG 100) and delivers the highest thermal onset (<i>T</i> _d,5% = 234 °C), but with poor cold-flow (pour point = 28 °C). Epoxidation affords very high viscosities (<i>ν</i> ₄₀ = 1.5-1.7 × 10³ mm² s^-1, VI = 30-40), best suited as thickeners rather than neat base stocks. Parent greases fall near ISO VG 32 (<i>ν</i> ₄₀ = 34-38 mm² s^-1) with pour points of 28-31 °C. These proof-of-concept results delineate application-relevant niches (high-VI light esters; VG 100 hydroxy-oils) and demonstrate a route to valorise non-edible fats into bio-derived lubricants.