PONGAMIA PINNATA SEED OIL FOR BIODIESEL FEEDSTOCK

        The malapari tree has a scientific name of  Pongamia pinnata (L.) Pierre, also known as kuanji in Balinese. Malapari is a legume tree that is able to fix nitrogen from the air through symbiosis with rooting bacteria called rhizobia. Adult malapari trees can reach 15 - 25 meters high, with a trunk diameter of about 50 cm with a branching spread. The flowers are compound bunches in white, pink and purple colors and are bisexual. The fruit is oval shaped, thick skinned with 1-2 elliptical brown seeds. The morphology of trees, flowers, fruits and seeds can be seen in Figure 1 below.

Figure 1. Morphology of malapari:  a) the tree, b) the flower, c) pods and seeds

        Malapari seeds contain oil which can be used as raw material biodiesel production. Malapari seed oil is non-edible so its use for biodiesel feedstock will not affect the price of edible oil. Biodiesel or biosolar is made by reacting plant oils or animal fats with alcohol in the present of a catalyst. The reaction of making biodiesel is called the transesterification reaction with a by-product of glycerin.

        The oil content of malapari seed l varies greatly depending on the location of growth. Some research results in India show that malapari seed oil content ranges from 10-47% of the dry weight of the seeds. The high diversity of oil content is very closely related to genetic factors, the environment and the interaction of both. The oil content of malapari seed grown in Bali needs to be investigated to see its potential as a raw material for biodiesel.

        The method used to extract oil from seeds is the sokhletation method using a set of sokhlet devices using hexane as a solvent. A sokhlet consists of an electric heating source called a mantle heater, a sokhlet tube and a condenser. The way to extract oil is to grind the dried malapari seeds to form a fine powder, then wrap them in filter paper. The sample is then put into the sokhlet tube. At the bottom end of the sokhlet tube is connected boiling flask that has been filled with hexane by ¾ volume. The upper end of the sokhlet tube is connected to the condenser which functions as a cooling jacket. Boiling flask is placed on the mantle heater and then ignited to start the extraction process. After all the oil has been extracted, the mantle heater is turned off and oil mixed with hexane is obtained, separated by distillation.

        The results of research on malapari seed oil content that grows in Bali ranges from 26% to 32% of the dry weight of the seeds. The variation in oil content is related to the environment where malapari trees grow, genetic factors and interactions between genetic and environmental factors that give rise to phenotypes. Trees with an oil content of 30% or more deserve further research both for their biodiesel potential and for their breeding.