The use of a mixture design technique to maximize the energy content of waste cooking oil (WCO) from catering establishments in Iran to make solid alcohol biofuel (SABF) was investigated. Original waste cooking oil (O–WCO) was centrifuged to obtain a supernatant (S–WCO) and a bottom phase (B–WCO) for biodiesel and SABF production, respectively. Micromorphology analysis showed the presence of fatty acid solid salts homogeneously scattered in ethanol at 100 °C and created a three-dimensional porous polycrystalline network after chilling, that enclosed the ethanol molecules and generated SABF. Optimal reaction conditions were 0.2 wt% alcohol, 0.0275 wt% NaOH, 0.7725 wt% B–WCO, and 45 min reaction time, for a maximum energy content of 8715.23 kcal/kg (36.46 MJ/kg), similar to natural gas, and higher than control groups, including SABF based on O–WCO, S–WCO, and butter, or some fossil fuels. Furthermore, this study investigates how the SABF heating value rose when the WCO's iodine value declined. This study demonstrated the feasibility of using SABF and candle wax, which has many advantages such as a high melting point, is environmentally friendly, produces no harmful gas emissions, has a long combustion time, leaves little combustion residue, is perfectly hygienic, and is easy to transport and storage.