Diesel is a popular source of fossil fuel energy, however, the emissions that its combustion can produce are of concern to environmentalists and those campaigning for cleaner air. In particular, with more regulations regarding CEC fuels – or those meeting Coordinating European Council standards – cleaner, oxygenated diesel blends are of greater importance all the time.
Ongoing studies investigating blending diesel with other components such as methanol and ethanol – otherwise known as OBFs, or oxygenated bio fuels – are hoping to lead to renewable and efficient fuels that generate low emissions and conform to regulations governing CEC fuels.
Need for fuel blends
Concerns about the availability of hydrocarbon fuels, along with emissions and production of greenhouse gases have encouraged improving the performance and quality of diesel. Blending diesel with oxygenated components renders it more environmentally friendly, more sustainable and helps it conform to the standards of CEC fuels.
A blend of ethanol and diesel is seen as desirable due to the easily renewable sources of ethanol, which include waste biomass substances, sugar cane, sorghum, molasses and barley. Ethanol and petrol blend quite easily, but diesel blends have been trickier. While a diesel and ethanol blend can be quite stable at temperatures in excess of 10 degrees Celsius, below this the fuel blend can split, especially when the ethanol component is 20 percent or more. Emulsifiers have been used in some circumstances.
As the price of ethanol has decreased, the production of reliably consistent e-diesel has become more pressing. Ethanol is desirable for blending with diesel due to its increased octane count, its higher flame activity, and increased vaporisation heats that can mean a higher ratio of compression, leaner burning, and shorter burn times. These features can increase the efficiency of a combustion engine.
DME blends are another option, as DME – dimethyl ether – is inexpensive, can be renewed, and can have enhanced levels of oxygen. DME can have a positive effect on emissions, but depending on the quantities blended, other aspects of performance can be affected.
Gas is another popular material for blending with diesel, as it has fewer negative effects on the environment and fits into the spectrum of CEC fuels. Burning gas generates fewer sulphonated by-products and nitrous oxides. In addition, gas has an increased octane rating, which can be a good match for combustion engines with a high to moderate compression ratio. Gas blends also have the potential for use in the advanced compression engine. Gas blends generally produce fewer toxic emissions and have the properties necessary for lean combustion. Environmentally and economically, gas diesel blends offer great potential.
As pressure rises from groups demanding fewer emissions and stricter standards on diesel, the need for oxygenated diesel and fuel blends is increasing. As technology grows more sophisticated, the physical problems of obtaining consistent quantities of oxygenated components for fuel blending should be overcome, paving the way for mass production of fuel blends that will satisfy environmental and performance criteria.