Japanese airline urges travellers to spend a penny to help save the planet

Japan's All Nippon Airways (ANA) is asking travellers on select flights to leave a little more than unnecessary baggage behind when they fly.

ANA passengers are being requested to use the toilet before boarding, in the hope that it will lead to a five tonne reduction in carbon emissions during the initiative's month-long trial period, which ends on 31 October.

Travellers on the carrier's 38 domestic routes and twice-daily international flights to Singapore will be reminded by ANA staff at departure gates to lighten their baggage and visit the toilet before boarding.

An average human bladder holds up to a litre of fluid, which weighs about 1kg. ANA's most widely used aircraft, the Boeing 777, can carry up to 247 people – equal to a maximum of 247kg of excess weight if all of them boarded with full bladders.

Similar calculations based on other toilet-related means of reducing passenger weight were unsurprisingly not available.

"Asking passengers to go to the toilet [before boarding] is just a small part of the programme," ANA spokeswoman Megumi Tezuka told CNN.

In addition to showing educational films on the environment, ANA is using recycled paper cups and plastic bottles instead of glass on the selected routes.

"We are making these items lighter – and making the passengers lighter, a little bit," Tezuka added.

Less weight translates into lower fuel consumption and thus less carbon dioxide emissions.

ANA said it plans to expand the programme if the trial proves successful.