An oil frequently found on your bathroom shelf may prove a viable alternative to diesel fuel for cars and trucks. Early tests show that jojoba-fuelled engines kick out fewer pollutants, run more quietly and for longer, and perform just as well as diesels. The search for alternative fuels, driven by dwindling oil reserves and concerns over exhaust emissions, has lead researchers to investigate more sustainable sources such as vegetable oils. Sunflower oil, soybean oil and even opium poppy oil have all been tested as potential fuels.
Now it is jojoba’s turn. Jojoba is a desert shrub that can reach up to 4.5 metres high and typically lives more than 150 years, producing nuts that yield half their volume in oil. The non-toxic oil is widely used as a non-greasy skin-smoothing ingredient in cosmetics, and as a base for shampoos and make-up.
Engineers think the oil has potential as a motor fuel because it releases a lot of energy when it burns and is chemically stable at the high temperatures and pressures in a working engine.
Dash of methanol
To test jojoba in engines, Mohamed Selim and his colleagues at the United Arab Emirates University in Al-Ain and at the Helwan University in Cairo, connected an array of sensors to a diesel engine and monitored its performance while burning regular diesel fuel.
They then ran the engine on a fuel called jojoba methyl ester, which they made simply by adding a dash of methanol and a catalyst to raw jojoba oil.
Selim’s team reveals in the journal Renewable Energy (vol 28, p 1401) that the jojoba fuel matched diesel for torque and power over the engine speeds they tested, between 1000 and 2000 revolutions per minute. What is more, the jojoba combustion gases took slightly longer to reach maximum pressure in the cylinder, which Selim believes may explain why the engine runs more quietly on the nut oil. Selim says jojoba is worth pursuing as an alternative fuel because it contains less carbon than fuels like diesel, which means lower emissions of carbon monoxide, carbon dioxide and soot.
And unlike diesel, jojoba oil contains no sulphur, so not only will the exhaust be free of harmful sulphur oxides, but the cylinders will be spared exposure to corrosive sulphuric acid, so the engine will last longer. Jojoba also has a higher “flashpoint” than diesel, meaning it is less likely to explode while being stored or transported.
Of course, growing enough jojoba would be a huge challenge. “The use of jojoba as a fuel needs huge quantities of seeds, which needs large investment, probably by the government or private sector,” says Selim. But while jojoba is unlikely to challenge diesel globally, it could gain popularity in certain regions. It can be grown in hot climates, salty soils and even deserts. “It needs to be cultivated in huge amounts, which is easy in the desert lands in many countries,” he says.
The plant has been grown for decades in the American south-west and north-west Mexico. It is now cultivated throughout South America and in several Middle East countries. Arable farmers in Egypt have already started planting jojoba shrubs specifically to use the nut oil as a fuel.