Biodiesel is an attractive alternative fuel for diesel engines.The feedstock for biodiesel production is usually vegetable oil, pure oil or waste cooking oil, or animal fats The most common way today to produce biodiesel is by transesterification of the oils with an alcohol in the presence of an alkaline catalyst. It is a low temperature and low‐pressure reaction. It yields high conversion (96%‐98%) with minimal side reactions and short reaction time. It is a direct conversion to biodiesel with no intermediate compounds. This work provides an overview concerning biodiesel production. Likewise, this work focuses on the commercial production of biodiesel. The Valdescorriel Biodiesel plant, located in Zamora (Spain), is taken like model of reference to study the profitability and economics of a biodiesel plant. The Valdescorriel Biodiesel plant has a nominal production capacity of 20000 biodiesel tons per year. The initial investment for the biodiesel plant construction is the 4.5 millions €. The benefits are 2 million €/year. The return of investment is calculated in less than 3 years. A biodiesel of 98% can be reached. The energy used for the biodiesel production is 30% less than the obtained energy from the produced biodiesel. Replacing petro diesel by the biodiesel produced in the plant, a significant CO2 reduction can be reached (about 48%). It means that the CO2 emission can be reduced by 55 000 tons CO2 per year. The production of biodiesel from sunflower oil and ethanol using sodium hydroxide as catalyst was performed in the laboratory and the results are discussed. The results are analyzed using the statistic method of Total Quality. The effect of the ethanol/oil ratio and the amount of used catalyst on the yield of biodiesel as well as on the properties of the produced biodiesel is studied. In the experimental part  the density, viscosity and refractive index of the produced biodiesel are measured. The ethanol/oil ratio influences the biodiesel production. The yield of biodiesel increases with the ethanol/oil ratio.  Regarding the influence of the amount of catalyst on biodiesel production in the studied conditions, an increase of the biodiesel yield with the amount of catalyst can be appreciated.   The study of the evolution of the transesterification during time shows that a reaction time of one hour is sufficient enough in order to reach the highest yield of biodiesel.