Next time you see a standard 40-feet shipping container have a closer look. It may be that your neighbors are moving… or it may be a modular-enclosed photo-bioreactor nurturing algae from which jet fuel can be made. This technology is truly amazing. The amount of algae you can produce at any one time depends on the surface area you can dedicate for the purpose. A large lake is a good candidate… but it takes up far too much space. Enter the shipping container. By a clever arrangement of the living space inside, it is possible to create 19,000 square feet of surface area in a single container!
Place a thousand of them near an industrial facility that produce waste CO2 to feed the algae, pipe sunlight into the containers via fiber-optic tubes hooked up to a parabolic collector and you are in business. All you need to add is an algae to oil converter (a mature technology) and you can start supplying the world’s airlines. Oh yes, the water used in the containers is recycled once the algae have been taken to the slaughterhouse. Sounds like science fiction? No, it is not. Such plants are being built as you read this.
Although electric propulsion in one form or another is the big thing in the automotive industry and a few electrically driven aircraft have been demoed recently, aviation is still a very long way from going electric, certainly in respect of larger aircraft.
There is a good deal more excitement about using bio-fuels in conventional jet engines. Only a short five years ago this subject was brand new and the corresponding science in its infancy. To-day, if anything, it is the multitude of technologies and competing solutions that is causing a problem for investors and developers alike. Which ones will be the winners? Where should the money go?
It looks like electric and hydrogen based propulsion systems are at a disadvantage for the time being. The power density of even the best current batteries is such that they are not really suitable for use on weight sensitive aircraft while the expensive new infrastructure hydrogen would need, not to mention its inherent dangers, makes for very slow progress, if indeed there is any progress at all.
With conventional kerosene becoming more expensive by the year and scarcity looming, finding an alternative is an imperative in itself. The fact that bio-kerosene can be used in what are basically conventional engines while the distribution and storage network can also stay more or less the same makes this type of fuel solution very attractive.
Technology choices there are aplenty. Let’s have a quick run-down, without necessarily being comprehensive, of what is available to-day and then let’s discuss some of the issues users or would be users of bio-fuels must face.
The classical methods are:
Fisher-Tropsch (F-T) is the process that has been used to create the fuel-blends used on the demo flights conducted by some airlines. It is a fuel that can be mixed with conventional kerosene.
HEFA or “hydroprocessed esters and fatty acids” is sourced from biomass feedstocks such as camelina, jatropha or algae. It is suitable for a 50-50 blend with conventional kerosene.
Then the new, upcoming technologies:
There is ATJ or alcohol-to-jet… I guess this will not be too popular in Ireland. But in fact your daily pint or snaps is not in danger. In this process, industrial waste gases, agricultural and forestry residues and municipal solid waste (your old shoes…) are converted to alcohols from which it is possible to make jet fuel.
DSHC or direct sugar to hydrocarbons involves genetically treated bugs that convert plant sugars to hydrocarbons.
In catalytic conversion plant sugars are converted to jet fuel but without bugs…
The thermochemical decomposition of biomass is called fast pyrolysis…
Then there is the gas fermentation process which converts flue gas from, for example, steel mills to ethanol and jet fuel is then made from that ethanol.
One thing common in all these new technologies is that they are trying to use materials and processes that do not require huge plots of ground suitable for food production to be converted to growing jet-fuel material. This is very important as the automotive industry will be able to tell you from bitter experience.
Like everything connected with aviation, fuel is also the subject of both technical and regulatory approval. It must meet very stringent requirements while it must also be suitable for use in existing engines without changes to the engines or a reduction in their service life. Just as an example, the fuels must have the proper aromatic content (similar to traditional kerosene) so that engine seals do not get damaged. Those seals are very special parts, crucial to the proper functioning of the engines. If they had to be replaced by seals made of a different material, it would cost a fortune…
Of course price is a crucial element in the bio-fuel equation. In the currently produced relatively miniscule amounts, they are still very expensive and only the research money being pumped into the system keeps the producers’ activities afloat. But it is clear already that the processes themselves can be made very efficient and most of the raw materials used are plentiful. True, production facilities may need to be located in unconventional places to be near the source of some of the more unusual raw materials but that in itself should not be a problem. There is no doubt any more that alternative fuels can be produced in the required quantities at prices that are competitive with kerosene derived from oil. This is especially true if we consider the most likely evolution of the price of oil in the coming years.
In the meantime, however, developing the appropriate specifications and approval process for synthetic jet fuel has kept a lot of people busy. This work is concentrated at ASTM International (formerly known as American Society for Testing and Materials (ASTM)) and the specification is called D7566. It now has two annexes, one for the Fisher-Tropsch (F-T) fuel blend and the other for the “hydroprocessed esters and fatty acids (HEFA) fuel. If you want to be a player in this field, you must achieve approval under D7566. The fuels resulting from the tricks we listed above will all have to get their own Annex as part of the D7566 specification if they are to be used in aviation. This is not easy but essential to ensure safety and consistency around the world.
Aviation is under tremendous pressure to reduce emissions on the one hand but also to find alternative fuels for aircraft equipped with conventional jet engines. The industry does not want to be hostage to the world oil market where increasing scarcity will push prices through the roof and supply may become a problem in the not too distant future. At the same time developers of alternative fuels see a tremendous opportunity for new business producing aviation fuel through a variety of technologies and from a wide range of raw materials, some of them industrial and municipal waste people may even pay for, to be taken off their hands. This is a match made in heaven.
The recent progress made on the alternative fuel scene is sending an important message also to the engine makers. They can develop their existing products and design new ones essentially staying on the same technology basis, without having to come up in a hurry with something revolutionary running on who knows what. This makes for cheaper engines in the short and medium term and better thought through solutions for the N+3 or +4 generation of engines that will not be needed for another 30 or 40 years for sure.
Cleaner aircraft running on old shoes…. Who could ask for a brighter future?