Biodiesel production from marine macroalgae Ulva lactuca lipids using novel Cu-BTC@AC catalyst: Parametric analysis and optimization

[Display omitted] •Soxhlet extraction resulted in a lipid yield of 10.17 % from macroalgae Ulva lactuca.•Cu–BTC@AC catalyst was successfully synthesized from lipid-extracted algae residue.•RSM–CCD enhanced the biodiesel yield to 92.56 % under mild reaction conditions.•GC–MS analysis confirmed the presence of 98.12 % FAME content in the biodiesel. The pursuit of renewable fuels for the transportation sector, particularly for combustion engines like diesel, is crucial in reducing greenhouse gas emissions. This study introduces an innovative strategy for biodiesel production utilizing marine macroalgae Ulva lactuca as the primary feedstock, emphasizing sustainability and resource efficiency. Lipids were extracted from the macroalgae via a Soxhlet process and characterized using GC–MS and FTIR to ascertain fatty acid composition and functional groups. The Cu–BTC@AC catalyst, synthesized from the lipid-extracted algae residue via pyrolysis and hydrothermal treatment, underwent characterization using SEM–EDS, XRD, and FTIR techniques. Subsequently, the Cu–BTC@AC catalyst was employed in the transesterification process to efficiently convert the extracted algal lipids into biodiesel, achieving a high yield of 92.56 % under RSM-optimized conditions: 65 °C temperature, 3.96 wt% catalyst amount, 15:1 methanol-to-lipid ratio, and 140 min reaction time. Kinetic and thermodynamic parameters for biodiesel production were calculated as follows: Ea = 33.20 kJ mol−1, ΔH# = 30.39 kJ mol−1, ΔS# = –165.86 J mol−1 K−1, and ΔG# = 86.48 kJ mol−1. GC–MS analysis identified a significant FAME content in the biodiesel, comprising 98.12 % of its composition. Notably, the Cu–BTC@AC catalyst exhibited excellent reusability, maintaining 80.21 % biodiesel yield after the third cycle. Moreover, physicochemical analysis of the biodiesel confirmed its compliance with ASTM D6751 specifications, underscoring its potential as a viable alternative fuel for the transportation sector.