The present study carries out the obtaining of biodiesel from residues of used cooking oil and tuna oil, to compare its carbon monoxide (CO) emissions with those of ACPM (commercial diesel). The production of biodiesel is carried out by means of a transesterification in an alkaline medium together with commercial ethanol in a reactor at 50 ° C, and the product obtained is purified by evaporation, with a reaction efficiency of 49%. Subsequently, a controlled combustion of samples of the product obtained and of ACPM is carried out in the motor of an automatic vertical steam boiler and it is evident that the CO's emissions of the product increase by 40% in a statistically insignificant way, as the adequate volumes of fuel to obtain sufficient information, however, the performance of the boiler engine does not decrease with the use of the product, which is why it can be considered as an efficient biofuel.