An American hotel is testing the altruism of travelers by offering nearly 50 percent off their room rates - in exchange for half a day of their vacation.

From this weekend, the hotel is slashing summer rates by up to 46 percent for guests who volunteer with one of two non-profit organizations during their stay.

Visitors can choose to either volunteer at a community kitchen between 8:30 am to 1:00 pm, or take part in litter picking or beautification projects near Lady Bird Lake, next to the hotel.

"Austin is an incredible vacation destination, but we thought, 'what if travellers could make it an even better place in the process of enjoying all the city already has to offer?'" says Tom Segesta, general manager of the 291-room hotel. "In the end, everyone benefits."

The package is available available May 1 through September 6, 2010.

"Voluntourism" has boomed in popularity in recent years, encouraged by jetsetting celebrities on humanitarian missions and the growth of travel agencies such as Hands Up Holidays and sites such as Planeterra.

Earlier this month, Copenhagen's Holiday Inn hotel offered guests a free dinner in return for physical activity, cycling to generate electricity for the hotel.