United says $30 million stake in biofuels maker will yield up to 180 million gallons in fuel

United Airlines is investing $30 million in a company that makes biofuels for airplanes.

United said Tuesday that the investment in Fulcrum BioEnergy Inc. could provide it with up to 180 million gallons of fuel per year.

That's just a drop in United's fuel consumption — the Chicago airline burned 3.9 billion gallons last year — and the investment is a tiny fraction of United's $1.1 billion profit last year.

Still, United Continental Holdings Inc. says it's the biggest single investment in biofuels by a U.S. airline.

Pressure is building on airlines to reduce carbon emissions from burning oil-based jet fuel. The Obama administration has taken early steps toward limiting emissions, following the lead of an international aviation authority.