Palm (Elaeis guineensis) is the most potential source of edible oils. Palm oil is now already produced and marketed in very large quantities, because it is edible and is high yielding (+/—3 ton/hectare/year). Direct injection (DI) diesel engine performance, exhaust gas emissions and some of fuel properties have been studied for biodiesel from CPO and Refined Bleached Deodorized Palm Oil (RBDPO), and these fuels blended with diesel fuel.21 It was found that both of biodiesel fuels and their blended fuels with diesel oil had increased BSFC levels, while the exhaust emissions (CO, CO2, HC and smoke) were better than for diesel fuel. Both DI and IDI22 engines were used for this research. These fuels were also used for a 2200 km fleet road test with two passenger cars and two trucks and compared with the performance of neat petrodiesel fuel.5 Parameters evaluated before and after road testing were fuel consumption, exhaust gas emissions, fuel injection equipment and engine lubricant.

Physic nut (Jatropha curcas) is one of the most potential sources of non edible plant oil. Physic nut seed oil is practically unexploited commercially, although it has the potential to replace or substitute palm oil as the raw material for biodiesel during the periods of high food sector demand.

The effect of biodiesel fuel from Jatropha curcas oil in DI diesel engines on the components of the engine influenced by fuel before (injection pump, injector) and after the combustion process (piston crown, cylinder head) was studied.23,25 The test bed procedure used was that commonly used for injection cleanliness evaluation adopted by World-Wide Fuel Charter (December 2002).26 Exhaust gas emissions such as NOx, CO, BSFC and engine lubricant before and after the test were also measured.

A single cylinder DI diesel engine fuelled with pure biodiesel from physic nut oil and blends (B10, B20, B50) with diesel fuel was used to compare engine performance and engine exhaust gas emission by comparison with diesel fuel.27 The results from this research show that biodiesel fuel from physic nut oil and its blends with diesel can give comparable engine performance for parameters torque (T), fuel volumetric consumption (FVC), brake specific energy consumption (BSEC) and thermal efficiency (ne). Engine exhaust gas emissions of total hydrocarbon (THC), CO and smoke emissions were reduced significantly when engine was run with biodiesel fuel. Biodiesel use resulted in slight increases of NOx emission.

Much research has been focused on the use of biodiesel and its blends in stationary DI diesel engines. Only a few studies on use of biodiesel and its blends in automotive diesel engines or indirect injection diesel engines have been done. The effects of biodiesel and its blends on an automotive IDI diesel engine by comparison with local commercial diesel fuel28 were studied in an experiment. Jatropha curcas methyl ester (JCME) and its blends had slightly lower torque, power output and thermal efficiency, but slightly higher BSFC than diesel fuel. In exhaust gas emission tests JCME and its blends significantly reduced HC, CO and Bosch Smoke Number but NOx emission slightly increased. The results indicated that B10 was the optimum fuel for the test engine.

A similar study carried out using both palm oil methyl ester (POME) and JCME with a DI engine yielded similar results.29 Coconut (Cocos nucifera) is an edible oil, but because it is widely distributed all over Indonesia in areas where it is often difficult to provide fossil fuels which are consequently high in price, it even becomes feasible to use coconut oil for fuel. Coconut methyl ester (CME) was field tested in vehicle and fishing boat engines as a fuel for use in remote areas.30 In the vehicle road test, B30 CME was used as fuel for 15 000 km, and in fishing boat engine, B100 CME was used for 200 hours. Results indicated that as long as the biodiesel quality was according to Indonesian Biodiesel standard SNI 04-7182-2006, there were no significant differences in engine operation during the test by comparison with diesel.

Kapok nut (Ceiba Pentandra L.) is a non edible oil. Kapok trees are also widely distributed throughout Indonesia but not utilised as an energy source.31 Biodiesel from Kapok seed oil was tested with a DI diesel using standard test procedures including engine injector nozzle coking test CEC F-23-A-01. Fuel consumption and smoke emissions increased. Nozzle tip deposits were very thick, presumably caused by the content of cyclopropenoid. Hydrogenation would be required to crack the cyclopropenoid structure before transesterification to solve this problem.

Mixed biodiesel.32 There is considerable potential for ASEAN to produce and supply various biodiesel products to the rest of the world due to its natural resource base; however, the use of biodiesel still presents a number of problems which need to be resolved, especially the high price of raw materials and the quality of biodiesel fuels. In view of these limitations, seeking ways to combine various biodiesel raw materials (e. g. edible and non-edible oils) is one strategy that could be used to solve the problems: reducing the economic cost, utilising the availability of raw materials and improving the quality of biodiesel fuels particularly cetane number, oxidation stability and cold flow properties. In this study, four biodiesel fuels were mixed to create three biodiesel fuel mixtures in differing weight ratios as follows: (1) 70% Jatropha curcas oil methyl-ester (JME) with 30% palm oil methyl ester (PME), (2) 70% JME with 30% coconut oil methyl ester (CME), and (3) 75% soybean oil methyl ester (SME) with 25% PME. Three kinds of mixed biodiesel fuels in form of B10 and B100 together with conventional diesel fuel have been tested in a DI diesel engine. Via analysing process based on the in-cylinder pressure data and rate of heat release, the obtained results showed that biodiesel fuel mixtures had similar cetane number to diesel fuel; this is the main factor to explain why three biodiesel fuel mixtures were selected to simulate the current used fuel — diesel fuel. Moreover, all mixed biodiesel fuels were comparable with conventional diesel fuel in performance and combustion efficiency and exhaust gas emissions were reduced significantly (e. g. THC, CO and PM). Especially, the reduction of NOx is an interesting issue in this study; this reduction could be explained by the rate of heat release obtained and the use of antioxidant BHA.