Biodiesel, a renewable fuel, is an important alternative energy option in terms of energy, environment, and economy. Biodiesel is produced from vegetable oil (algae-oil, animal tallow and used oil can also be used) and alcohol by transesterification reaction with glycerol as by-product. Current methods use soluble catalysts (60° C, ~100 min) that pose separation and product contamination issues. Our idea was to use solid catalysts to produce biodiesel employing ethanol as a critical fluid medium as well as a reactant. Critical region of the alcohol is desired for the mixing of alcohol and oil phases, which are otherwise immiscible, to minimize mass transfer limitations. The aim was to develop a continuous process (packed bed) for commercial biodiesel production. Metal oxides, manganese oxide, titanium oxide, calcium titanate, calcium aluminum oxide and copper oxide, were identified as effective solid catalysts from batch tests. Critical reaction regime (260° C, 1000 psi) gives conversions ~ 95 % in 5 ~ 20 min. The process can handle feedstock with high free acid content (to exploit cheap feedstock) unlike the conventional process that requires an additional acid-catalyzed step preceding the main base-catalyzed step. Catalysts have been tested successfully against performance deterioration over time. The process eliminates additional processing units associated with the conventional process, such as, separate catalyst-alcohol mixing unit before reactor, catalyst neutralization unit, water-washing steps to remove soap and catalyst, and, contaminated glycerol refining unit. The process will not have waste water disposal problems unlike the conventional process. The process can be termed as totally green. Biodiesel potential and pending studies would be discussed.