Fuel options for commercial aircraft: An overview

Engr S A Mansoor Petroleum based fuels are extracted from below the earth's surface. Similar to underground water, it is found in geological strata of rocks or shale below the ground. It is now established that the liquid, commonly called crude oil, was formed, eons back, through geologically induced compressive decomposition of plants and vegetation, as more rocks and soil mass was deposited by water flowing down from snowy mountains or coming from natural fissures or lakes, connected to underground water sources. From these underground geological structures, we pump out the crude oil, which is then refined by fractional distillation into various types of usable petroleum products as fuel and lubricants. This is today the largest, and, in fact, the only source of energy and power, which provides transport for people and goods all over, across land, sea and air; that covers the travel routes across the globe. Given the fact, we can say that it is plants and vegetation which are processed by nature, giving us the fuel for all forms and types of transport facilities. The logical corollary is why we do not grow these plants and vegetation, and decompose them and produce crude oil! Though theoretically it is possible, the cost involved for generating the huge pressure and temperature for conversion will be enormous, to say the least. It is, therefore, far cheaper to pump out the crude oil and refine it! Bio-fuels are directly sourced from plants, and can be refined and used as fuel. The process can be compared to the one for preparing oil like corn oil, soya oil and similar other edible types of oil. Possibility is there that we can also grow our fuel, that has gradually led to the development and making of bio fuel as an energy source for powering transport vehicles, which today run on gasoline or diesel oil. It is used in all modern jet aircraft, where it is called Aviation Turbine Fuel (ATF). It has now come into use, to some extent, for motor vehicles. However, its development and application to the marine sector has still not been established and documented, both for inland and overseas marine vessels. In the rapidly developing air transportation sector, not much is known about the developments with bio-fuels; though a few well documented trials have been carried out starting from the last decade of the twentieth century. At that time, development work has been undertaken in some European countries and the USA, where airplanes, aircraft engine manufacture and air transportation industries are well established. Most of the information in the aviation sector is closely related to commercial air transport. Very little authentic information, however, has come from Russia and China, where use of a substitute for fossil fuel is being attempted; and work on producing bio-fuels finally is said to be not far away. However, no significant breakthrough in the utilisation of bio-fuel has possibly been made yet. It would have set off a storm in the world media. In the USA, aircraft designers, engine makers and commercial aircraft manufacturers have experimentally evaluated the advantages of using bio-fuels. The reason behind this development has been more strategic rather than commercial. The USA naturally wants to curtail dependence on imported petroleum fuels; particularly because of the oil's location in the troubled Middle East. Here the superpowers' influences are being polarised, that can hamper future oil supplies! Bio-fuels have been substituted for kerosene (ATF), the present-day fuel for almost all types of jet aircraft; both for civil aviation and the armed forces. In December 2008, Air New Zealand flew a commercial Boeing 747 aircraft, with one of its four engines running on a 50:50 blend of ATF and bio-fuel, sourced from the 'Jatropa' plant. The test flight, replicating all normal flights and weather patters possible, was fully recorded and videoed throughout the flight from takeoff to landing! In early 2009, other commercial carriers, Virgin Atlantic (British) and Continental Airlines (US) have also carried out similar tests with their commercial aircraft. Also in January 2009, Japan Air Lines similarly flew a Boeing 747-300 aircraft with one engine using a 50:50 blend of ATF and bio-fuel from three different plant sources now available --- Jatropa, Alge and Camalia plants. All the three different plant-based biofuel sources were blended 50:50 with ATF, separately for these special flights. The aircraft was flown with maximum engine thrust; and with fuel pump shutdown and restart during flight! All the three fuel blends used performed to full satisfaction. The flight was monitored by a team of engine makers and the airline's operational and test personnel, both on board the test flight, and the ground! Meanwhile, in another historic but defining way ahead in a new direction, Boeing Aircraft Company, makers of large or jumbo-jet commercial aircraft, went a step further ahead into the future! They made aviation history during February and March of 2008, by having a test flight, without using any fuel. They used fuel cells to power the aircraft throughout the flight. All these are known and recorded facts in the aviation sector. It confirms the viability of using bio-fuels for commercial aircraft. However, in this scenario, we come across the usual dilemma. It goes: What comes first - the chicken or the eggs? With ATF, now being used for commercial aircraft, its price is much cheaper in real terms, when compared to all the cost of cultivation of plants and then converting the fruits or seeds to bio-fuel. In the plants for making this fuel, capital cost is involved, which leads to higher product cost. This makes it more expensive than normal ATF; hence the operating costs will definitely be higher on a BTU basis. So long as kerosene is easily available, and adequate refining capacity is available, and the sources are easily accessible, the venture to establish bio-fuel refining plants and its storage and supply facilities will be a risky commercial venture considering the high interests for the capital involved. Also the time and efforts, all of which are translated in terms of money, make bio-fuel rationally a very poor second or the last option for the foreseeable future! This is commercial reality that discourages the development, and hence availability and, ultimately, the use of bio-fuels. Only when supplies of crude oil are restricted for one reason or another, can bio-fuel make headway. It could be that political events in the Middle East, which has an impressive volume of crude oil, can come to such a stage, were the extraction and transport of oil refined there is no longer possible due to adverse geo-political realities in the area, and where a long-drawn Arab-Israeli conflict can upset the situation at any time. The reality of using bio-fuel in aircraft is well established. However, only time and political situations can tell when it will find a regular market as the energy source of motive power for transports. ............................................................. The writer is an engineer, with over half a century of management job at mechanical and chemical industries. E-mail: sam@dhakacom.com