Flying on Vegetation

Airlines, aircraft companies, and other stakeholders are taking the long view in developing sustainable alternatives to petroleum-based jet fuels.

Fuel is expensive for airlines. According to sources interviewed for this article, fuel accounts for 30 to 50% of operating costs, depending on the size of the aircraft. And fuel prices remain volatile.

In May 2014, an Airbus A330-200 of KLM Royal Dutch Airlines used a 20% blend of sustainable fuel made of used cooking oil, for a 10-h flight from Schiphol airport in Amsterdam to the Dutch Caribbean island of Aruba. It was part of a pilot project in the European initiative called ITAKA (Initiative Towards sustAinable Kerosene for Aviation), with the fuel supplied by SkyNRG. (Airbus)
At the same time, there are few alternatives to powering aircraft. While land transport has some available options— think electric vehicles and hydrogen fuel cells—aviation depends on liquid fuels with high energy density. Emissions are another concern. According to the Air Transport Action Group (ATAG), aviation is responsible for 2% of global manmade CO² emissions.

Fuel supplies may be stressed even more as worldwide air travel demands continue to grow. According to the Boeing 2014 Current Market Outlook forecast, world passenger traffic will continue to grow at a rate of 5% annually. Similar forecasts come from Airbus.

Fuel price volatility, increasing demand, emissions from fossil fuels, and lack of alternatives are pushing the industry into a search for renewable, sustainable, low-carbon alternatives such as biofuels.

Fuels, Certifications, and Challenges

A key issue is sustainability. To be sustainable, suppliers must produce biofuel through non-destructive agriculture and in doing so emit no more carbon than its product saves. Boeing describes sustainable biofuel as emitting 50 to 80% less carbon compared to fossil fuel.

Another constraint for biofuel suppliers is that aviation industry needs “dropin” fuels—fuels that can blend directly with petroleum jet fuel without requiring modification to existing jet engines, airplanes, or fueling infrastructure.

To ensure compatibility, ASTM must approve the fuel before aviation regulatory agencies would allow its use, according to Dr. Ric Hoefnagels. He is a Researcher with the Copernicus Institute of Sustainable Development, part of Utrecht University in The Netherlands. He contributes to the Climate-KIC project Fuel Supply Chain Development and Flight Operations (Renjet). The project includes partners such as Schiphol, KLM Royal Dutch Airlines, SkyNRG, and Imperial College London, among others. The goal is to create a self-sustaining network of regional renewable jet fuel supply systems in the European Union, and Renjet is grappling with aviation biofuel issues ranging from supply to compatibility.

Brazilian airline GOL committed to fly its Boeing 737 fleet with up to a 10% blend of the renewable fuel farnesane. Initial flights were to begin in July 2014.
“Until recently, there were only two ASTM-certified pathways for jet fuel production from biomass,” he explained. One is hydro-processing of esters and fatty acids (HEFA) using vegetable oils or used cooking oil as feedstocks. This is sometimes referred to as Bio-SPK. The vast majority of commercial flights on biojet have been fueled by HEFA fuels.

While initial capital cost is lower, “the main issue [for Bio-SPK] is that those fuels are quite expensive,” said Hoefnagels. “It is really difficult to reduce these costs because either the supply potential is limited, as in the case of used cooking oils; or the cost is in the feedstocks, as in the case of vegetable oils.”

Another certified pathway uses high-temperature gasification of biomass or waste, such as municipal waste, which is converted into syngas. The syngas is then subjected to Fischer-Tropsch synthesis reaction to form synthetic paraffinic kerosene, sometimes called FT-SPK. The synthesis process in its essence is similar to coal-to-liquid (CTL) or natural gas-to-liquid (GTL) refining, and is similarly capital-intensive. It requires large, complex refineries.

“However, it has potential to reduce cost in the future,” Hoefnagles said, though it requires large investments in research, development, demonstration, and deployment.

ASTM in a June 2014 press release announced approval of a third type of fuel, Renewable Synthesized Iso-Paraffinic (SIP) aviation biofuel for use in commercial airplanes through its ASTM D7566 specification. This followed an announcement by Amyris and Total that the companies are preparing to market a drop-in SIP jet fuel that contains up to 10% blends of farnesane, a renewable biofuel that is made from plant sugars and will be blended with petroleum jet fuel. Amyris uses a proprietary process for converting sugars into jet fuel, using a pathway they call Direct Sugar to Hydrocarbon (DSHC). This will open biofuel development in places like Brazil, where Amyris is using sugarcane or other plants with a high sugar content, such as sugar beets.

Future Projects and Technology

Salicornia is showing promise in sustainable aviation biofuel research at Masdar Institute of Science and Technology in Abu Dhabi. (Boeing)
“There is only so much arable land and fresh water to go around,” said Michael Lakeman, Regional Director of Biofuel Strategy for Boeing Commercial Airplanes, in an interview with Aerospace & Defense Technology. “It’s important to make a paradigm shift in thinking about biofuel production. Instead of viewing biofuel as a “food or fuel” situation, develop new models where producing biofuel enables more food production—producing “food and fuel.”

A pilot project that Boeing is helping to fund in the UAE is doing just that. Conducted by the Sustainable Bioenergy Research Consortium (SBRC) at the Masdar Institute of Science and Technology, a program will evaluate the feasibility of producing biofuel using desert plants called halophytes. These are saltwater-tolerant and can be irrigated with seawater. Other funding partners include Etihad Airways and Honeywell UOP. SBRC research to date has found that entire shrub-like halophytes, such as salicornia, can be turned into a biofuel more efficiently than many others.

The key to sustainability is to think beyond jet fuel to integrate aviation biofuel production into regional aquaculture, or fish farming, Lakeman said. “Fish farms produce a lot of waste, which is a real challenge.”

Typically, effluent from aquaculture operations, when pumped back into natural water bodies, causes pollution or eutrification from algae blooms. With the system being developed in the UAE, fish waste is used as fertilizer to grow the halophytes. In the process it cleans the seawater, which is returned to the ocean, Lakeman explained.

He admits there are challenges, including domesticating a wild plant for the first time. “There is a lot of work, and we know it is not a short-term win here.” It's a long-term play that could pay off big.

Sustainability Today

This infographic from the Sustainable Bioenergy Research Consortium depicts the Integrated Seawater Energy and Agriculture System (ISEAS).
An example of current biofuels distribution is the company SkyNRG. According to Sierk de Jong, a researcher with the Copernicus Institute and part-time employee of SkyNRG, the company was founded in 2009 as a joint venture with KLM, Spring Associates, and Argos Oil, a downstream oil distributor. Its mission is to develop a market when there are no producers or buyers of aviation biofuel.

Price remains a key obstacle that SkyNRG has been tackling. De Jong describes the fuel from SkyNRG as Bio-SPK. “In 2009, sustainable jet fuel was twenty times more expensive than fossil kerosene," he said. "We have today driven it down to two or three times.”

Even so, airlines are reluctant to pay even that. So, the price premium is cofunded through corporate clients associated with KLM. “Eventually, with technology developments, I believe that we can drive down the price further,” said de Jong.

“Because it’s a specialty product," he continued, "there is currently very little dedicated sustainable jet fuel production capacity in the world. Creating scale is crucial. So SkyNRG’s main long-term effort lies on increasing production capacity. The company is teaming up with governments, airlines, and airports around the world to create so called “BioPorts”—regional dedicated supply chains to produce sustainable jet fuel.”

Markets and Investments

Etihad Airways conducted a 45-min demonstration flight on Jan. 18 with a Boeing 777-300ER powered in part by the first sustainable aviation biofuel produced in the UAE.
Both Boeing’s project with Masdar and the SkyNRG joint venture confirm observations from PwC’s survey in April 2014 gauging interest in the total biofuels market. About 52% of the executives surveyed were optimistic about aviation biofuels. Brian Carey, PwC's U.S. Cleantech Advisory Leader, told Aerospace & Defense Technology that “a number of players see biofuels as the Holy Grail, helping to guarantee price stability.”

However, the Holy Grail is not upon us yet. The technology needs to improve and the industry needs to scale up to drive costs down. Carey pointed out that price parity is vital to acceptance.

What he is observing is the difference in the type of organizations willing to make the investments needed to finally achieve that price parity.

“Four or five years ago," he said, "there was a fair number of venture capital investments in early-stage advanced-biofuels companies. Some [biofuel] companies tried IPOs too soon; these companies were trying to do too much too fast.”

Today he is seeing investments from airlines, airplane OEMs, and others with a strategic stake in the development of biofuels—including a few select oil and gas companies.

“Airlines are willing to pay for pilot projects,” he said. “They are willing to put in place joint ventures with advanced biofuels companies to keep their options open.”