Jelliarko Palgunandi
DEPARTMENT OF CHEMISTRY KYUNG HEE UNIVERSITY, SOUTH KOREA

It is inevitable that we have to start thinking more seriously about the problem of limited availability against the growing need for fuel. Biodiesel as one of the renewable fuels sourced from vegetable materials is now receiving special attention from the audience of scientists and industrialists in Indonesia and the world.

The Indonesian government predicts that by 2025, renewable energy consumption will reach 17 percent of total consumption, with a percentage of 5 percent for the use of biofuels (both biodiesel and bioethanot). Indonesia's biodiesel development roadmap states that in 2011-2015 the use of biodiesel reached 15 percent of total diesel engine fuel consumption and then 20 percent in the 2016-2025 period.

Gl and G2 biodiesel development

So far, first-generation (Gl) biodiesel has been produced and widely used, both in its pure form and as a blend with petroleum-derived diesel fuel. What is Gl biodiesel? Biodiesel is known as fatty acid methyl ester (FAME), which is obtained from the transesterification of vegetable oil (triglycerides) with methanol using a catalyst. For every conversion of one molecule of triglyceride, three molecules of FAME and one molecule of a by-product, glycerol, are produced.

Gl biodiesel, although declared slap applicable, still has some compatibility issues with current diesel engines. Among these are corrosion due to the high atomic oxygen content of FAME and the maximum concentration allowed as a blend with petroleum-derived diesel oil (petrodiesel).

In relation to carbon dioxide (CO2) emissions, the contribution of CO2 emissions from FAME combustion is also feared to be relatively high (due to the high oxygen content of FAME). To overcome this problem, second-generation (G2) biodiesel with specifications close to petrodiesel has been developed.

In principle, G2 biodiesel is a hydrocarbon derived from vegetable oil that undergoes a hydroprocess. Through this route, various vegetable oils, animal fats, or blends of biomass and petroleum, and even used vegetable oils (e.g., waste cooking oil) can be processed at the same time to produce various hydrocarbon fractions that are ready for refining.

Thus, it is different from the hydrogenation of vegetable oils in the food industry, which is not intended to produce fuel. In the hydroprocessing of vegetable oils, a series of reactions occur in the form of hydrogenation of the double bonds of carbons, decar-boxylation (removing carboxylic groups), decarbonylation (removing carbonyl groups), isomerization, and cracking.

Hydroprocessing of crude vegetable oils offers a more efficient process without producing byproducts, except water and CO2. Moreover, hydroprocessing to produce biodiesel directly can utilize established petroleum refining technologies.

Why G2 biodiesel?

Hydroprocessing can produce G2 biodiesel with lower oxygen content, even close to zero, so engine corrosion problems can be avoided. Likewise, the emissions from burning G2 biodiesel contain less carbon.

Biodiesel from hydroprocessing is also very compatible with the conditions of diesel engines in use today because it can achieve a cetane number of 55-90 (compared to the cetane number of diesel oil currently in circulation of 4045). Under these conditions, the permissible concentration of biodiesel in petrodiesel biodiesel blends will be higher without the need to modify the engine equipment.

One of the drawbacks of G2 biodiesel may be that it freezes easily at temperatures below 20 degrees Celsius. Of course, this problem is only relevant in four-season regions, while in Indonesia it is not an issue at all. This can be overcome by adding catalysts or blending.

Until now, G2 biodiesel has not been used commercially, but several large industries are ready to produce it in mass sizes. UOP (A Honeywell Company), an American company, as well as Petrobas, Brazil, the copyright holder of vegetable oil hydroprocessing, are pioneering the production of G2 biodiesel with a capacity of up to 400 kilotons per year. Can Indonesia start?