Characterization of biodiesel produced from waste oil and washing water as biodiesel production waste

Although the use of waste oils which are very harmful for the environment, the beneficial use of biodiesel seems as an environmental solution. The pollution levels of the wastes produced during this process should be evaluated. Hence, it is aimed to determine the properties of biodiesel produced and to evaluate waste washing waters in terms of pollutant parameters. This study was carried out in two steps: In the first instance, the characterization of biodiesel and washing water which produced from domestic waste frying oil by using three different catalysts was carried out under laboratory conditions. Methanol was used as alcohol and NaOH, KOH, MgO were used as catalyst for biodiesel production from waste frying oils. In the second step, 30 experimental sets were formed with the experimental design including different ratios of methanol as alcohol and KOH as catalyst with different reaction times and temperature conditions. For each produced biodiesel, aqueous and dry washing was performed. After the aqueous washing process of biodiesel, chemical oxygen demand (COD), phosphate (PO4), sulfate (SO4), nitrate (NO3), total kjeldahl nitrogen (TKN), total nitrogen (TN), conductivity, pH and wavelength screening of the formed washing water were performed. The pH, density and viscosity of the produced biodiesel were measured and their conformity to American biodiesel standards (ASTM D-6751) was evaluated. The effect of aqueous and dry washing on biodiesel efficiency has been compared. In addition, in some selected samples by using gas chromatography (GC) long-chain fatty acid composition was also examined. It is among the best quality biodiesels that meet both ASTM D-6751 and TS EN 14214 standards. DN3, DN8, DN12 and DN27 (alcohol ratio (v/v) 30% and catalyst ratio (w/w) 1%) were obtained in the aqueous washing purification. In dry washing purification, DN5, DN15 (alcohol content 20%), DN7, DN8, DN12 and DN24 (alcohol content 30%) were obtained. In general, optimum alcohol and catalyst ratios were determined as 30% and 1% respectively. It has been found that the determinants of biodiesel quality were predominantly alcohol and catalyst. The detected optimum values for temperature and duration are 70°C and 75 min respectively. It has been reported that in the experiments with high alcohol and catalyst ratio, the pollution of the waste washing water is low and in the experiments with low alcohol content, the pollution is quite high. Keywords: Waste oil, Biodiesel, Dry washing, Water washing, Washing water, Pollutants