Quality Improvement of Biodiesel from Rubber Seed Oil by Blending with Biodiesel from Jatropha curcas Oil

Abstract

This research aimed to utilize rubber seeds oil and Jatropha curcas oil as raw material for biodiesel, to increase cetane number from rubber seed biodiesel, and to decrease viscosity from Jatropha curcas biodiesel. The proximate analysis of raw materials result showed that rubber seeds and Jatropha curcas seeds contained 37.96% and 41.66% of oil, respectively. Both types of seeds oil were separated using hydraulic hot press machine and the separation of rubber seeds gave 12.35% of yield and 13.12 % of free fatty acid, while the separation of Jatropha curcas seeds gave 18.34% of yield and 2.10% of free fatty acid. Esterification-transesterification process for biodiesel production was applied for rubber seeds oil and transesterification process to produce biodiesel from Jatropha curcas oil. Rubber seeds oil was esterified by using methanol and sulfuric acid 5% as catalyst for 1 hour and 300-500 rpm. Subsequently, rubber seeds methyl ester and Jatropha curcas oil were transesterified by using methanol and 1% sodium hydroxide as catalyst for 1 hour and 300-500 rpm. The result shows that cetane number from rubber seeds biodiesel and Jatropha curcas biodiesel sequentially were 46.35 and 53.7 and the viscosity was respectively 4.86 cSt and 6.16 cSt. Blending 20% rubber seed oil with 80% of Jatropha curcas oil and 20% rubber seed biodiesel with 80% of Jatropha curcas biodiesel increased cetane number of rubber seed biodiesel to 52 and 51.8, respectively, and decreased the viscosity of Jatropha curcas biodiesel to 5.92 cSt and 5.75 cSt, respectively.

Biodiesel merupakan salah satu sumber bahan bakar alternatif pengganti bahan bakar fosil. Keuntungan menggunakan biodiesel antara lain: ketersediaan bahan baku bersifat kontinyu, ramah lingkungan, kandungan sulfur rendah, dan dapat menurunkan emisi gas buang. Sumber bahan baku biodiesel yang potensial di Indonesia yang tidak dikonsumsi manusia sebagai bahan pangan yaitu biji karet (Hevea brasiliensis) dan biji jarak pagar (Jatropha curcas). Biji karet memiliki keunggulan antara lain : lahan yang tersedia cukup banyak, harga bahan baku masih relatif rendah dan belum dimanfaatkan secara maksimal, viskositas biodiesel lebih rendah dari biodiesel jarak pagar. Bilangan setana biodiesel biji karet masih dibawah SNI ataupun ASTM. Jarak pagar sebagai bahan baku biodiesel memiliki keunggulan dalam hal daya adaptasi tanaman tinggi, produksi minyak cukup tinggi, dan memiliki bilangan setana yang tinggi. Viskositas biodiesel jarak pagar cukup tinggi.