Methyl levulinate synthesis from rice husk employing e-waste derived silica supported nano CuO–CdSO4 photocatalyst: Assessment of production environmental impacts, engine performance and emissions

Applications of E-waste recovered silica (support) and copper citrate (precursor) for the synthesis of nano CuO–CdSO4 doped photocatalyst (NCCP) for subsequent employment in sustainable conversion of rice husk (RH) to drop-in biofuels viz. methyl levulinate (ML) have been explored. The prepared NCCP (low Eg = 2.0 eV) was employed for alcoholytic depolymerization (AD) to produce ML from holocellulose (HOC) extracted from RH through infrared assisted delignification. Taguchi orthogonal design predicted the optimal values of the AD viz. HOC: Water (1:5 w/w), NCCP concentration (1 wt%), HOC: methanol (1:30 w/w) and AD time (125 min) rendering 96.97% ML yield deploying combined ultrasonication-UV energies at 60 °C; saving 30% energy compared to conventional heating system. Noticeably, this is the first insightful investigation on the application of ML as a diesel additive demonstrating significant diminutions (25.92% and 83.33% for CO and HC) in harmful emissions. The LCA of the overall ML synthesis indicates remarkable reduction in environmental pollution with 63.63% and 66.66% mitigations in GWP and ecotoxicity respectively. Thus, a sustainable ML synthesis protocol encompassing the development of E-waste derived nanophotocatalyst through conversion of rice husk and its successful use as a diesel additive could be established.