Green extraction technologies for coconut oil-based biodiesel production in the Philippines: A critical review

Philippine biodiesel production relies almost entirely on coconut oil (CNO) as feedstock for coconut methyl ester (CME), a dependence increasingly strained by supply volatility.Recent efforts to raise blending mandates further were suspended after adverse weather sharply reduced coconut output and drove up CNO prices.Expanding CME supply therefore requires new feedstocks or better recovery from the existing one.Oil palm diversification remains constrained by heavy import dependence, leaving CNO recovery the more immediate lever.This review critically evaluates four green extraction technologies -microwave-assisted, ultrasound-assisted, enzyme-assisted, and supercritical fluid extraction (SFE) -against conventional milling and against one another, then ranks each technology's Philippine readiness through an Analytic Hierarchy Process weighing evidence maturity, feasibility, oil quality, efficiency, and environmental criteria.SFE emerges as the clear front-runner, backed by the most direct coconut-specific evidence among the four and compositional advantages unmatched elsewhere, including pressure-tunable lauric acid enrichment exceeding 50% and consistently low peroxide values; the ranking holds under alternative weightings.Its principal barrier is economic rather than technical: high-pressure equipment demands capital investment ill-suited to a smallholder-dominated, low-unit-value commodity feedstock.Pairing SFE with in situ transesterification to consolidate extraction and conversion could offer a route to offset this cost, alongside pilot-scale validation on Philippine copra.Doing so could position CNO recovery as a durable lever for meeting the Philippines' stalled biodiesel blending targets.