Waste Lubricating oil regeneration technologies: A review of applicability in developing economies

This review provides the first integrated analytical framework for evaluating waste lubricating oil (WLO) regeneration technologies; acid-clay treatment, solvent extraction, vacuum distillation, adsorption polishing, and hydro-treating, through the combined lenses of process design readiness, economic feasibility (CAPEX/OPEX), product quality (API Group classification), and decentralisation potential for developing economies. Unlike previous descriptive catalogues, this study introduces standardised techno-economic comparison across all technology categories and proposes a validated modular hybrid system (vacuum distillation coupled with adsorption polishing) specifically engineered for resource-constrained infrastructure realities, with Zimbabwe as a representative case study. Three principal findings emerge: (i) hybrid vacuum-adsorption systems (75-85% yield, moderate-high quality) achieve optimal compromise for decentralised contexts, (ii) adsorption polishing can functionally substitute for hydro-treating at 3-5% of capital cost, reframing selection criteria toward context-appropriate solutions; (iii) Zimbabwean domestic regeneration of around 10000 tonnes/year could displace 3-10% of lubricant imports (saving USD 2 - 3 million annually) while diverting 30,000 tonnes/year from improper disposal. The proposed modular system offers a validated pathway translating laboratory feasibility into economically sustainable industrial reality in developing economies.