SCM method has a drawback toward commercialization of the process with the high cost of apparatus due to the high temperature and pressure. The addition of co-solvents, such as carbon dioxide, propane and hexane can decrease the operating temperature, pressure and the amount of alcohol. Co-solvents with increasing the miscibility of oil and alcohol aid the mixture of alcohol–oil to become a single phase [12–14]. The gaseous co-solvents such as CO2 and propane, can be separated easily from the products by expansion and be recycled directly while the liquid co-solvents such as n-hexane and tetrahyrdrofuran require additional separation steps [15]. Carbon dioxide is non-toxic, nonflammable, inexpensive, environmentally benign, has a low critical temperature of 304.4 K and a moderate critical pressure of 73.9 bar. CO2 also is a good solvent for the non-polar compounds, such as hydrocarbons and essential oils [16–19]. Table 1 shows a list of reported operating conditions for production of biodiesel using SCM. As shown in Table 1, the co-solvent utilization can lead to the high biodiesel yield via SCM at moderate operating conditions.