There are numerous publications on solid base-catalyzed transesterification with regards to their properties and catalytic activities. The solid base catalysts have shown high catalytic performance on high quality vegetable oils. On the contrary, poor catalytic performance is observed for low quality vegetable oils due to the presence of significant amounts of free fatty acids, which results in soap formation. An alternative way of processing these low quality vegetable oils is by using an acid catalyst. The drawback is that homogeneous acids such as hydrochloric acid and sulfuric acid need longer reaction time and may pose corrosion problem to the equipment. Table 3 lists some of research findings on biodiesel conversion using different solid acid catalyst. Findings show that acid-catalysed reaction needs high temperature and longer time for high yield of conversion.