Jet-biofuel: is real bio?

Aviation biofuel is widely considered by the aviation industry to be one of the primary means by which the industry can reduce its carbon footprint.

Aviation biofuel is widely considered by the aviation industry to be one of the primary means by which the industry can reduce its carbon footprint. After a multi-year technical review from aircraft makers, engine manufacturers and oil companies, biofuels were approved for commercial use in July of 2011. Since then, multiple airlines have begun the use of biofuels on commercial flights . 

The International Air Transport Association (IATA) thinks a 6% share of sustainable 2nd generation biofuels is achievable by 2020 and Boeing supports a target of 1% of global aviation fuels by 2015. This is in support of the goals of the aviation industry reaching carbon neutral growth by 2020 and a 50% decrease in carbon emissions by 2050 .

The American Section of the International Association for Testing Materials (ASTM) approve the use of biofuels in July of 2011. This allows the airlines to fly passenger jets using derivatives of up to 50 percent biofuel made from feedstocks such as algae and wood chips. It will help carriers that account for 2 percent of global carbon dioxide emissions reduce pollution blamed for damaging the Earth’s atmosphere. Jet fuel is a mixture of a large number of different hydrocarbons. The range of their sizes is restricted by the requirements for the product, for example, freezing point or smoke point. Jet fuels are sometimes classified as kerosene or naphtha-type. Kerosene-type fuels include Jet A, Jet A-1, JP-5 and JP-8. Naphtha-type jet fuels, sometimes referred to as "wide-cut" jet fuel, include Jet B and JP-4. "Drop-in" biofuels are biofuels that are completely interchangeable with conventional fuels. Deriving "drop-in" jet fuel from bio-based sources is ASTM approved via two routes.

The first route is bio-SPK (Bio derived synthetic paraffinic Kerosene). Bio-SPK involves using oil which is extracted from plant sources like jatropha, algae, tallows, other waste oils, Babassu and camelina to produce bio-SPK by cracking and hydro-processing. The growing of algae to make jet fuel is a promising but still emerging technology. Algae fuel uses algae as its source of natural deposits. Harvested algae, like fossil fuel, release CO2 when burnt but unlike fossil fuel the CO2 is taken out of the atmosphere by the growing algae. Among algal fuels' attractive characteristics: they do not affect fresh water resources, can be produced using ocean and waste water, and are biodegradable and relatively harmless to the environment if spilled. Algae cost more per unit mass (as of 2010, food grade algae costs ~$5000/tonne), due to high capital and operating costs, yet are claimed to yield between 10 and 100 times more energy per unit area than other second-generation biofuel crops. One biofuels company has claimed that algae can produce more oil in an area the size of a two car garage than a football field of soybeans, because almost the entire algal organism can use sunlight to produce lipids, or oil. The United States Department of Energy estimates that if algae fuel replaced all the petroleum fuel in the United States, it would require 15,000 square miles (39,000 km2) which is only 0.42% of the U.S. map. This is less than 1⁄7 the area of corn harvested in the United States in 2000. However, these claims remain unrealized, commercially. According to the head of the Algal Biomass Organization algae fuel can reach price parity with oil in 2018 if granted production tax credits.

The second route is FT SPK (Fischer–Tropsch Synthetic Paraffinic Kerosene). This process involves processing solid biomass using pyrolysis to produce pyrolysis oil or gassification to produce a syngas which is then prossessed into FT SPK. Jet fuel from the Fischer–Tropsch process using natural gas and coal. Using natural gas as a feedstock, the ultra-clean, low sulfur fuel has been tested extensively by the U.S. Department of Energy and the U.S. Department of Transportation. The Air Force, which is the U.S. military's largest user of fuel, began exploring alternative fuel sources in 1999. On December 15, 2006, a B-52 took off from Edwards AFB, California for the first time powered solely by a 50–50 blend of JP-8 and FT fuel. The seven-hour flight test was considered a success. The goal of the flight test program is to qualify the fuel blend for fleet use on the service's B-52s, and then flight test and qualification on other aircraft. The test program concluded in 2007. This program is part of the Department of Defense Assured Fuel Initiative, an effort to develop secure domestic sources for the military energy needs. The Pentagon hopes to reduce its use of crude oil from foreign producers and obtain about half of its aviation fuel from alternative sources by 2016. With the B-52 now approved to use the FT blend, the C-17 Globemaster III, the B-1B, and eventually every airframe in its inventory to use the fuel by 2011. 

But just because the prefix “bio-” is tacked on the word “fuel” doesn't necessarily mean it creates less pollution. Conventional fossil fuels sometimes result in less overall carbon dioxide emissions than biofuels, points out a Massachusetts Institute of Technology study recently published online in the journal Environmental Science and Technology. As we know, many airlines, have started using blends of conventional jet fuel with fuel produced from plants. The biofuels can help the companies cut costs, but are they really better for the environment? Only if the plants they come from are grown in ecologically sensitive ways, says James Hileman, principal research engineer in the department of aeronautics and astronautics at MIT. "What we found was that technologies that look very promising could also result in high emissions, if done improperly," reports Hileman in an MIT press release. "You can't simply say a biofuel is good or bad ‚ it depends on how it's produced and processed, and that's part of the debate that hasn't been brought forward, says Hileman.

Hileman and MIT graduate students Russell Stratton and Hsin Min Wong examined the carbon dioxide produced during the life cycle of 14 fuel sources, including conventional petroleum-based jet fuel and "drop-in" biofuels: alternatives that can directly replace conventional fuels with little or no change to existing infrastructure or vehicles. Growing crops for jet fuel production often entails clearing forests or using machines that also burn fuel. Drilling for oil takes energy, too. Then the raw materials from both sources have to be transported and processed. "All those processes require energy," Hileman says, "and that ends up in the release of carbon dioxide.  People don't often think of coal-to-liquid fuel production as a green option, remarks Hileman. But "severe cases of land-use change could make coal-to-liquid fuels look green," he says. On the other hand, the study points out many forms of biofuel that are more environmentally sensitive and produce less pollution. Many of these truly “green” biofuels have common characteristics. They can grow on marginal lands and don't compete with food for prime fertile land, and they also create useful by-products. Hileman notes that many of these by-products can further reduce the overall carbon dioxide release from the biofuels.

For example, converting jatropha, a shrub that can grow in poor soils and dry areas, to biofuel also yields solid biomass: For every kilogram (2.2 pounds) of jatropha oil produced, 0.8 kilograms (1.8 pounds) of meal, 1.1 kilograms (2.4 pounds) of shells and 1.7 kilograms (3.7 pounds) of husks are created. These by-products can be used to improve soil, prevent erosion or feed animals, or be burned for heat or electricity production.

All in all, the transition to biofuels is a complicated subject. Hileman notes that this research is only one lens through which biofuels can be viewed. The costs involved and crop yields are important considerations as well.