Aircraft Aviation Fuel Future

At this time (2007) the supply of normal crude oil is estimated to last another 40 years with current yearly demand (1000 barrels per second according to Wikipedia). At some point, increasing demand together with higher oil prices, will make alternative resources very attractive. Even current so called depleted oil wells still contain enough oil, some 40% of the oil could still be in the well requiring new techniques to extract. Other theories claim that oil is being replenished by processes deep in the earth (abiogenic petroleum), making it virtually renewable and of unlimited supply.

To show you how much oil there is, we have a comparison of worldwide distribution of normal conventional crude oil and thick heavy oil reserves
Heavy Oil Reserves

It is important that a stable price of oil should be set by the oil producing and consuming countries for a certain period of time in stead of being set by daily fluctuating and wildly speculating markets, which introduce too much economic uncertainties and with a negative result for the world economy as a whole. The current oil futures trading is flawed and legislation should be created to control it and create a more transparent system. Some US Senators have been asked by airline carriers to take steps.

As aircraft are bound (still) to a liquid fuel (it has the most energy content per weight) these alternative resources need to be converted into liquid fuels. There are three possibilities: gas to liquids, coal to liquids and biomass to liquids. We will scratch the surface of these three processes and the effect of aviation on the environment.

Gas to Liquids

GTL uses a process developed by two Germans in the 1920s, Franz Fischer and Hans Tropsch, and thus called the Fischer-Tropsch process. This process converts natural gas into synthesized gas and this syngas is then converted into hydrocarbon products like diesel fuel (Vpower), wax and more. This process produces very pure synthetic hydrocarbons free of sulphur, aromatics and more usually found in 'normal' hydrocarbon fuels.

This process is commercially in operation since 1992 in South Africa and 1993 in Malaysia. Both plants produce somewhere around 60000 bpd total. Recent projects are being started by different companies (Chevron, Shell and ExxonMobil) to increase production with another 400000 bpd the next few years.

The proven natural gas world reserve is enough for another 60 years with current demand. Speculative reserve indicates enough gas for some 200 years to come.

At this moment a number of international companies are working together to research the use of GTL fuel in aircraft engines. The source for this fuel would be coal, gas or other biomass. The expectation is to start using this fuel for flight tests in a 50/50 mix for JET A/A1 by the end of 2008 and to switch over to a full SYNJET A/A1 by 2010 (SYNJET = Synthetic JET).

In 2009, engine manufacturer Rolls-Royce together with Boeing, Air New Zealand (B747-400) and Virgin Atlantic will do tests with biofuel based on algea sources. The USAF has already done a number of succesfull flight tests on a C-17 Globemaster, B-52 and a Rockwell B-1B aircraft. This biofuel was mixed in a 50/50 ratio with JP-8 fuel. They expect to certify biofuel for general use in 2011.

Coal to Liquids

Coal reserves are far bigger than natural gas or oil together. Coal is mainly (80%) used to generate electricity, but efficiency is low and emissions are at a high level. Not a very clean solution. Gasification of coal via the coal to liquids process is the cleanest solution to use coal. It uses the same process as GTL.

Coal to liquids process is not as clean as for natural gas. There are more issues to it than with GTL, more investments, more solid byproducts and higher CO₂. CTL will be limited the next 10 - 15 years but as oil and gas resources deplete it is likely to become an important source for energy.

Coal reserves on this planet should be enough, with current demand, for another 80 years. Speculative reserves indicate coal reserves for another 500 years.

Biomass to Liquids

Biomass has been used in the last century when it was replaced by oil and natural gas. At this time the only visible use of biomass energy source is in biodiesel and gasoline. Its either being used at 100% (B100) of mixed in any ratio with petroleum diesel, usually 20% (B20). Gasoline is also mixed with fuel derived from biomass.

There are a number of benefits from using biomass as a energy source:

• It lowers NO_x, SO_x, CO₂ and other greenhouse gasses
• Biomass is renewable and low carbon
• Degradable, non toxic, easy to store and use
• Resource diversity: animal waste, forest residue, plants, algea
• Creates economic growth in agricultural area's
• And growing fields, forests and plant eat up CO₂!

A number of factors influences it attractiveness: inconsistent energy densities depending on resource used, burns inconsistent. It should be possible to meet all the worlds energy requirements but the technical and economical potential is lower. It is expected that biomass can supply around 25% of the energy demand.

Some biomass sources are: algea (the best option), wood, straw, organic waste (you know the type), sugar beet, rapeseed, sunflower. These can be converted using processes like: combustion, Gasification, pyrolysis, digestion, hydrolysis and fermentation (bio ethanol) and extractification and esterification (biodiesel).