A BOEING 747 flew from London’s Heathrow to Amsterdam’s Schiphol Airport to conduct the test flight which was partially fueled with a bio-fuel mixture of coconut and babassu oil in one of its four main fuel tanks. The jet carried pilots and several technicians, but no passengers.

This bio-fuel would produce much less carbon-dioxide gas (CO2) than regular jet fuel, because CO2 emissions on a normal flight are generally three times the fuel burned. But there are a lot of unanswered questions about the usefulness of bio-fuels in the battle against global warming. This test flight is the latest example of how the world’s airlines are jumping on the environmental bandwagon by trying to find ways of reducing aviation’s carbon footprint. These efforts have included finding alternative jet fuels, developing engines that burn existing fuels more slowly, and changing the way planes land.

Aircraft engines cause noise pollution and emit gases and particulates that reduce air quality and contribute to global warming and global dimming, where dust and ash from natural and industrial sources block the sun to create a cooling effect. Boeing 747-400 jet and its engines did not have to be re-designed to use bio-fuel on this test flight.

But, why the coconut oil and Babassu oil are selected as bio-fuels for jet airplanes? It is because both coconut oil and babassu oil have the similar properties and can be considered as twin oils of the same category. That is why the mixture of coconut oil and babassu oil has been used in the test flight.

In general, many vegetable oils have similar fuel properties to diesel fuel, except for higher viscosity and lower oxidative stability. If you compare kerosene oil, which is used as airplane fuel or home heating fuel, with the coconut oil you will find that kerosene is not viscous like coconut oil and its specific gravity is simply 0.81 which means 810 grams per litre and therefore lighter than water.

The density of petroleum diesel is about 850 grams per liter whereas petrol has a density of about 720 g/L, about 15 per cent less. When burnt, diesel typically releases the energy of about 40.9 Mega Joules (MJ) per litre, whereas gasoline releases 34.8 MJ/L, about 15 per cent less. Diesel is generally simpler to refine from petroleum than gasoline and therefore it is cheaper than petrol in Pakistan.

The cost of diesel traditionally rises during colder months as demand rises for heating oil, which is refined in much the same way. Due to its higher level of pollutants, diesel must undergo additional filtration which contributes to a sometimes higher cost. In many parts of the United States and throughout the UK, diesel may be higher priced than petrol.

The average chemical formula for common diesel fuel is C12H23, ranging from approx. C10H20 to C15H28. Biodiesel can be obtained from vegetable oil (vegidiesel / vegifuel), or animal fats (bio-lipids), using transesterification. Biodiesel is a non-fossil fuel alternative to petro-diesel. It can also be mixed with petro-diesel in any amount in modern engines, though when first using it, the solvent properties of the fuel tend to dissolve accumulated deposits and can clog fuel filters.

Bio-diesel has a higher gel point than petro-diesel, but is comparable to diesel. This can be overcome by using a bio-diesel/ petro-diesel blend, or by installing a fuel heater, but this is only necessary during the colder months. A diesel- bio-diesel mix results in lower emissions than either can achieve alone, except for NOx emissions. A small percentage of bio-diesel can be used as an additive in low-sulphur formulations of diesel to increase the lubricity lost when the sulphur is removed. In the event of fuel spills, bio-diesel is easily washed away with ordinary water and is non-toxic compared to other fuels.

Babassu oil is a clear light yellow vegetable oil extracted from the seeds of the babassu palm, which grows in the Amazon region of South America. It is a non-drying oil used in food, cleaners and skin products. This oil has properties similar to coconut oil and is used in much the same context. It is increasingly being used as a substitute for coconut oil. Babassu oil is about 70 per cent lipids.

There are great opportunities to utilise coconut oil as a fuel in the Pacific. Coconut oil can be blended with diesel fuel and under certain conditions totally replace it. Coconut oil in Pacific islands countries is increasingly used in both transport and electricity generation due to its lower local cost. Other benefits include the support to local agro-industries.

The use of bio-fuels is nearly as old as the diesel engine itself, as Mr Diesel himself designed his original engine running on peanut oil. During periods in history when regular diesel supply was hampered seriously such as during World War II, throughout the world, the vegetable alternatives from different sources have been used in different forms.

Figure 1 gives an overview of the options to use coconut oil in compression diesel engines. Coconut oil can be blended with diesel, straight in an adapted engine or turned into bio-diesel. Because of higher specific density and slightly lower energy content, the specific fuel consumption using coconut oil is generally eight per cent higher.

Even though there is quite some evidence of the environmental benefits using vegetable oils as a fuel, it is the local cost of fuel that is the real driver behind these developments in the Pacific island economies. Electric utilities generally suffer from great dependence on imported diesel for the power generation and are seeking new ways to hedge these risks.

Motorists have successfully blended coconut oil with diesel to decrease the costs per km. For coconut oil fuel to be a sustainable alternative to diesel fuel in the Pacific, the restructuring of the coconut industry and replanting of coconut plantations is required. Widespread utilisation of alternative fuels will require active involvement of engine manufacturers and local mechanics.

Engine testing indicates that vegetable oils can readily be used as a fuel or in a range of blends with diesel. Long-term engine research however shows that engine durability is questionable when fuel blends contain more than 20 per cent vegetable oil. Especially deposits on the pistons, valves, combustion chambers and injectors can cause severe loss of output power, engine lubricant deterioration or even catastrophic failure to engines.

Using pure coconut oil in standard engines is very attractive through its low cost. However, it requires special technical supervision and may shorten engine life. As the coconut oil has up to 30 times higher viscosity than the regular diesel at the same temperature, most engine modifications include a fuel heater. As heat is exchanged between the engine coolant and the fuel, the oil viscosity approximates that of diesel. As the coconut oil solidifies below temperatures of 25¢ªC, often an electrical heater is incorporated in the fuel tank.

Biodiesel is a standardised fuel that consists of vegetable oil Methyl Ester. It is a product of vegetable oil that reacts with an alcohol (methanol) and a catalyst (sodium hydroxide). This process generates two products: glycerine, which can be used in soap production, and biodiesel.