The effect of different drying methods and microalgae species on the quality parameters of biodiesel obtained by transesterification technique

Abstract

In the study, seven microalgae species called Nitzschia sp., Nannochloropsis sp., Botryococcus braunii, Neochloris oleoabundans, Schizochytrium sp., Chlorella vulgaris L., and Chlorella variabiilis L. were dried by four drying methods: spray, convective, vacuum, and microwave. Biodiesel was produced from dried microalgae via transesterification.The vegetable oil yield was the maximum in spray and vacuum dried Schizochytrium with 35.50 and %34.53, respectively. Similarly, the highest biodiesel yield with 100% was obtained in Schizochytrium dried by spray technique. However, the cloud point of -1.77 degrees C was the lowest in Botryococcus braunii samples dehydrated by microwave drying. The highest pour point with -10.13 degrees C was obtained in microwave dried Chlorella variabilis samples, but the maximum freezing point was found in the microwave and convective dried samples of Chlorella variabilis with -13.60 and -13.70 degrees C, respectively. The lowest water content was measured in biodiesel samples from Botryococcus braunii, Chlorella vulgaris, and Chlorella variabilis dried by microwave technique. However, the best results regarding calorific value were found in Schizochytrium samples dried by spray and vacuum. The viscosity with 6.08 mm2 s-1 and density with 0.90 g cm-3 of Botryococcus braunii dried by the microwave method were at the maximum.Interestingly, two species commonly used in biodiesel production, Chlorella vulgaris and Chlorella variabilis, could not meet the expectations regarding quality parameters. Also, Schizochytrium and Nitzschia were determined as the most suitable microalgae species for the quality standards for biodiesel production. Compared to the others, the most successful results were obtained in the biodiesel produced from Schizochytrium dried spray drying.