Additionally, it can also be noted in Table 2 that the drying methods at high temperature(70 °C,105 °C) had a negative impact on lipid composition giving lower saponifiable matter, thereby decreasing the potential biodiesel yield when compared to standard method. Despite the lower temperature used for fume hood and sun drying, the lipid content extracted from these dried sludge decreased to 12.3% and 11.4%, respectively, again compared to standard MgSO4·H2O method,
26.3%. Finally, freeze-drying also showed a significant loss of extracted lipids (11.2%) but ,in contrast,the rate of saponifiable matter was higher(57.3%) than those from oven at 70 °C (53.9%), sun (45.5%) and fume hood (44.8%) drying methods. The low lipid content extracted from
dried sludge at low temperature and freeze-drying reported here is in agreement with Cordero Esquivel et al. [8]. They reported that biomass drying by both freeze-drying and oven drying at low temperature(30 °C) caused an approximately 70% loss of total lipid content [8].