Alcohol may be known as the demon drink but a growing number of people are billing alcohol-to-jet (ATJ) fuel as having the potential to save the aviation industry from its dependence on fossil fuel. As with any movement, though, there are staunch and vociferous critics who doubt the reality of such claims.
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.
LanzaTech produces ATJ by capturing vented gases from industrial plants to generate fuel-grade ethanol through a gas-to-liquid process
Critics, however, argue that the amount of energy needed to convert these feedstocks 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".
© Virgin AtlanticVirgin Atlantic aims to use LanzaTech biofuel to support demonstration flights within 18 months
One ATJ producer taking a very different approach to Byogy is New Zealand-based LanzaTech, which captures vented gases from heavy industrial plants such as steel mills to generate fuel-grade ethanol through a gas-to-liquid process. LanzaTech supplies this ethanol to Swedish BioFuels, which converts it into synthetic jet fuel. Last year the company partnered Virgin Atlantic, which aims to use the fuel to support demonstration flights within 18 months.
LanzaTech chief executive Jennifer Holmgren says the company has built a demonstration facility in Shanghai that produces 100,000gal (379,000 litres) of ethanol a year.
"We will attach a jet fuel facility to this, which will use Swedish BioFuels' technology to convert the ethanol into jet fuel - hopefully in the second half of this year, but I'm not 100% sure," says Holmgren. "If we add the jet fuel facility at demo level then it will produce 50,000gal of jet fuel a year, but if we tap into the commercial market it could produce 15-20 million gal of jet fuel annually."
LanzaTech has agreements with two steel companies in China, both intending to build commercial facilities, and memoranda of understanding with two Korean steel firms. To produce 200 million gal of jet fuel a year, LanzaTech would need to have agreements with eight to 10 steel companies, says Holmgren.
The company already has a pilot plant in New Zealand which produces 15,000gal of ethanol a year. "By 2016-2018 we should be in pretty good shape in terms of having a significant volume [of jet fuel], which would be about 250 million gal a year," she adds, noting that "certainly by 2020" prices should come down to comparable levels with kerosene.
A key advantage of LanzaTech's fuel over other ATJ sugar-derived fuels is it is "outside the food chain", says Holmgren. LanzaTech's process is being billed as a win-win solution because it captures carbon that steel mills would otherwise emit into the atmosphere. This is what attracted Virgin Atlantic, says the carrier's head of sustainability Emma Harvey: "This is a very attractive proposition because it uses a waste stream. The ability to capture and reuse, we thought was ground-breaking." Harvey says Virgin Atlantic will "keep an eye on anything else but over the next two to three years [ATJ fuel] offers the best opportunity".
Through its agreement with LanzaTech, Harvey believes there is the potential for Virgin Atlantic "to uplift all our fuel as a 50:50 mix from Shanghai and later from Delhi". Virgin Atlantic is hopeful the technology can eventually be brought to the UK to support its London Heathrow operations.
About 65% of the world's steel mills could be converted to turn captured gases into ethanol, says Harvey, which would meet 19% of the airline industry's annual fuel requirement.
But Bowers believes the LanzaTech process is "too good to be true": "Fermenting these gases to jet fuel suggests a lot of wishful thinking. Processing the off-gases would mean a large plant as fermentation is not an instantaneous process. It would take time. Again, there would have to be a lot of energy in the distillation process."
Colorado-based Gevo is another major player in the ATJ market, and is focusing on retrofitting ethanol plants to make isobutanol. "We've figured out how to produce isobutanol with no by-products," says Gevo president Chris Ryan. Gevo is retrofitting a commercial ethanol plant in Minnesota to make isobutanol. Ryan says the plant will be ready in the first half of this year. It also has a demonstration plant near Houston with capacity to produce 10,000gal of ATJ fuel a month. Gevo will ship IBA produced at Minnesota to the Houston plant to be converted into jet fuel.
In January, Gevo made its first shipment of ATJ fuel to the US Air Force as part of a contract it has with the US Department of Defense (DoD) to supply 11,000gal of ATJ. "Gevo was awarded the first ATJ contract by the USAF so they can do fit-for-purpose testing," says Ryan. "Once completed, I hope they'll run a request for proposals for additional volume to test it across a variety of Air Force platforms."
Gevo has also signed a letter of intent to supply fuel to United Airlines. "The quantities could be extremely large but it all depends on economics. It depends on the cost of carbohydrates versus the cost of oil," says Ryan.
Outlining the advantages of ATJ fuels over alternative fuels already certificated, Ryan says: "Most biojet used today comes from vegetable oil, plant oil or animal fat, and the challenge is quantity and cost. It's impractical to get to the scale the aviation industry needs to significantly reduce its carbon footprint. But carbohydrates are the most abundant feedstock in the world, so getting to scale at a low cost is the main advantage [of ATJ]."
Ryan estimates 20 billion gal of ethanol a year is being produced globally and if all ethanol plants were retrofitted to produce isobutanol, they could produce 15 billion gal of jet fuel a year - 20% of the airline industry's annual fuel demand. However, he admits that while technically possible, "it's unlikely the economics would make a wholesale shift happen. But expanding the markets for fermentation alcohol assets is always interesting. It will depend on ethanol incentives and margins".
It will also depend on demand, but Ryan says there is no shortage. "Airlines and the US DoD have really stepped up and created the kind of pull in the marketplace that makes producers respond. There's a tremendous pull. This really helps and will accelerate the timeline."