Methyl ester content of PSME presents high purity at 96.9 %wt, whereas sediment provides lower methyl ester content only at 47.68%wt which mainly contains palmitic acid methyl ester and oleic acid methyl ester. This result can be considered that PSME contains other chemical composition, which is not methyl ester, aggregating as sediment.When this composition is aggregated, it could induce methyl ester compositions to aggregate as well.This is consistent with the result in Figure 6 that relative composition of each methyl ester in both PSME and sediment are not significantly different.The sediment is hypothesized as glyceride compounds. Therefore, these samples were determined by GC to evaluate glyceride composition (Figure 7). As expected, there are much greater fractions of both mono- and di-glyceride in sediment than that in PSME.This is implied that even the biodiesel conforming to the specification limit for monoglyceride (with high melting point at 74-76 oC) could induce other methyl esters to co-precipitate as glyceride compounds.