Germany's biggest airline, Deutsche Lufthansa AG, says it has begun trial flights using biofuels in a bid to reduce carbon dioxide emissions.

Lufthansa said Friday that an Airbus A321 flying the Hamburg-Frankfurt route four times daily will use a 50/50 mix of regular fuel and biosynthetic kerosene in one of its two engines for the next six months.

The airline says during the test period the use of biofuel will reduce CO2 emissions by up to 1,500 tons.

German environmental group BUND criticized the project, saying any short-haul flight is bad for the environment compared with train travel.

In another effort to reduce emissions and fuel use, Lufthansa said Monday it will begin using a new plastic cargo container that is 15 percent lighter than the traditional aluminum ones.