Those in favour of ATJ fuels point to the wide availability of feedstocks - principally sugarcane - that can be fermented and distilled into ethanol and subsequently converted into jet fuel. This, say proponents, means it has a much better chance of being scaled up to commercially viable quantities once certificated than other alternative fuels that have already received the ASTM International stamp of approval.
Critics, however, argue that the amount of energy needed to convert these feed-stocks into the end-product cancels out the environmental benefits of burning ATJ fuels when the whole life cycle is taken into account. Opponents also doubt claims that the cost of ATJ fuels can be reduced to compare with the cost of kerosene any time in the near future.
Despite such criticism, airlines such as Virgin Atlantic and Qatar Airways have thrown their weight behind companies developing ATJ fuels, as has the US Department of Defense, which is in the process of trialling ATJ fuels produced by global chemicals company Gevo. Each company developing ATJ fuels adopts a slightly different process or feedstock, but they are all unified in their belief ATJ fuels will be approved for commercial use by certificating body ASTM International within two years and, following that, can be rapidly scaled up.
One such company is California-based Byogy Renewables, which claims to have produced the world's first 100% replacement for kerosene by bolting on its own back-end process to an ethanol plant to convert the ethanol into jet fuel via catalytic synthesis. "We've invented a process that converts alcohol to jet fuel. Most companies take the alcohol to someone else to turn into jet fuel," says Byogy chief executive Kevin Weiss. "This is a 100% replacement jet fuel from the most abundant feedstock in the world - sugar."
But the abundance of sugarcane as a feedstock is questioned by Stephen Bowers, a Germany-based specialist in evaluating feedstocks for petrochemical production. "Is sugar viable as a feedstock? In my opinion, no. The lowest cost of sugar production will come from cane sugar grown in a tropical climate [such as] Brazil," says Bowers.
"Global sugarcane production is close to two billion metric tonnes and Brazil is about 650-700 million tonnes per annum. In theory, Brazil could produce about 55 million tonnes of ethanol if all the sugarcane was processed into ethanol. On a global scale, sugarcane could produce 150 million tonnes of ethanol. Global jet fuel demand is something like 200 million tonnes and rising," Bowers adds.
Weiss believes the key advantage ATJ fuels have over fuels derived from hydroprocessed esters and fatty acids (HEFA) - which were certificated for commercial use by ASTM International on 1 July 2011 and have since been used to partially power commercial flights by a number of airlines - is that they do not have to be blended with kerosene because they already contain aromatics.
"HEFA fuels require massive hydroprocessing - the fuel has to be taken to an oil refinery. We're completely different - the fuel is made at our site and is ready for distribution at a fraction of the cost," he says. Weiss is hopeful ASTM certification for ATJ fuels can be achieved by the end of 2013 or the middle of 2014. "It's not a matter of if ATJ will get approved, it's a matter of when."
Qatar Airways has signed an agreement with Byogy to use its fuel once certificated. The selection of ATJ fuel and Byogy followed a year-long feasibility study by Qatar Airways "to see what kind of technologies are out there and what feedstocks are available locally and globally, and to find out if biofuels for aviation are feasible", says the airline's senior manager of corporate responsibility, environment and fuel optimisation, Chris Schroeder.
The feasibility study led Qatar Airways to believe "ATJ is probably going to be the frontrunner when it comes to biofuel for aviation", says Schroeder. "We engaged with Byogy 18 months ago and we threw our weight behind them. We wanted to push for ATJ with aromatics because we're looking in future to possibly blend it with GTL [gas-to-liquid fuel], which contains no aromatics."
In 2009, Qatar Airways operated a commercial flight between London Gatwick and Doha using an Airbus A340-600 with all four Rolls-Royce Trent 500 engines powered by a 50:50 blend of GTL and Jet A1 kerosene. The airline has teamed up with Qatar Petroleum and Shell, which have built a GTL plant in the gulf state. Schroeder says the carrier has received a "very, very promising" sample of ATJ fuel from Byogy. "We have signed an off-take agreement with them whereby whatever fuel they produce, once certified, we'll take it for the next couple of years. So with that, they can go into the venture capital market and raise capital."
Schroeder believes ATJ will be "the mainstay" of alternative fuels for aviation because "the feedstock is there in large quantities and certification is nearly there". However, he admits the industry is "in its infancy" and it will be a long time before ATJ can be scaled up to such a level it makes a significant impact on aviation's carbon footprint.
"It will be at least another decade and even then it will not be close to 5% or 8% of jet fuel because aviation is growing and this [growth] will slow everything down," says Schroeder.
Bowers has "grave reservations" about Byogy's claims, accusing the company of "pinning their technology to some magic breakthrough in cellulosic ethanol technology to somehow bring the price down to economic levels". While Schroeder says that "on paper the figures look good" and the price of Byogy's fuel "is relatively close to what we're paying for jet fuel", he admits that "until we really go into production, we don't know".
Read More @ Source: Flight Global