Lufthansa, Finnair, KLM and British Airways all plan to use a mix of traditional fuel and biofuels made from plants and cooking oil to power their flights.

2011 is turning into the year of sustainable jet fuel.

On 15 July, Lufthansa began flying between Hamburg and Frankfurt using a 50/50 mix of traditional fuel and biomass fuel made from plants. On 20 July Finnair went one step further, flying from Helsinki to Amsterdam -- the longest route thus far -- using a 50/50 mix of jet fuel and biofuel made from cooking oil retrieved from restaurants.

Dutch company SkyNRG, which supplied the biofuel used to power Finnair’s Airbus engines, is also supplying KLM with fuel for 200 Amsterdam-to-Paris flights that start in September. Starting 28 July, low-cost airline Thomson Airways will fly one biofuel flight a week, from Birmingham, England to Palma, Spain. Even the 2050 conceptual hypersonic plane that makers say will be able to travel from Los Angeles to Tokyo in two-and-a-half hours at speeds of up to Mach 4 will be powered partly by biofuel.

With traditional jet fuel costing so much, both wallet- and climate-wise, and with 1.5 to 1.7 billion barrels consumed annually worldwide, it is not surprising that many airlines, including Virgin, Continental and Japan Air, are looking into alternative fuel sources. British Airways recently teamed up with Solena, an American company that turns household, urban and agricultural waste into fuel. According to SkyNRG, biofuels will be commercially viable for airlines to purchase when they are just 1% of the total supply of all jet fuel, which could happen by 2015.

Biomass fuel is created from plant crops (like sugarcane, hemp, even algae) and other types of waste like recycled cooking oil. Critics argue that the eco-friendly fuel has its own carbon costs and takes land away from planting edible crops. But Lufthansa says the jatropha and camelina plants that make up their fuel would not have been grown on land that is part of food production. And SkyNRG, which claims to have a sustainable supply chain, from “feedstock to flight”, argues that each “green route” makes this type of fuel more accessible and affordable.