Jukka Peltonen has just come home from the shop with a bag of clementines, but he's disappointed to discover they're too acidic for his taste.

Instead of throwing them out, Peltonen, the head of a public relations firm, offers them to his neighbours by placing them in a communal pantry located in the cellar of his apartment complex in the Helsinki suburb of Roihuvuori.

The pioneering project, aimed at reducing food waste among the complex's 200 residents, has been in place for the past four months, and is part of a growing worldwide trend of initiatives undertaken by consumers to live greener lives, such as carpooling, composting and city biking.

The pantry, used by the two buildings in the complex, is loaded with goodies: yoghurts close to their expiry dates, cold cuts still in their wrappings, cheese, bread, fruits and vegetables, and drinks.

Each user registers their visit on a clipboard hung by the door to the pantry, located in a room kept at six degrees Celsius (43 degrees Fahrenheit) year-round.

"You give your apartment number, you say if you brought or if you took something, and if you want, you leave a small commentary," explains Peltonen, 51, sporting a tweed cap and closely-shaven beard.

A Facebook page itemising the stocks is also kept up to date.

There is no legal framework regulating this type of food sharing, instead it's based on trust among residents.

"Since last week, we can leave whats left of home-made dishes. The one leaving them there must describe the ingredients. If he (lies), or if somebody gets sick, he knows hes responsible," says Peltonen.

The anti-waste project is the brainchild of Heikki Savonen, 44, who came up with the idea two years ago.

"I was thinking, why not create a Facebook for food, on a neighbourhood or even on a city level, to avoid wasting food," recalls Savonen, a stylist who bubbles with new ideas. He got in touch with the food sustainability research centre MTT Agrifood Research Finland.

After launching the idea on Internet, he ended up contacting the residents of the Roihuvuori apartment buildings.

"It was perfect. With a hundred apartments, the size matched our criteria. And the residents were heterogeneous: some families, some old people and students living alone," Savonen says.

MTT Agrifood Research hails the project as forward-thinking.

"Producing food that is then thrown away is a large and unnecessary burden on the environment," says Juha-Matti Katajajuuri, a researcher at the institute. Finnish households throw away 130,000 tonnes of food each year.

In Roihuvuori, there's room to grow: so far only about a dozen people leave regular comments on the clipboard.

"Lets be realistic. Some people will never use it," Peltonen admits.

"There are also secret users: they use the system but they dont write anything. For instance, old people think its shameful to take other peoples food, so they do it without telling," he adds.

"In summer, people will go out more. There may be more participants then," he suggests.

After four months, it's hard to tell if the project has reduced the users' monthly grocery bills, but Savonen says that's not the most important thing.

"After a while, this project could create a sense of community. People could greet each other in the building's corridors, and say to each other: 'the pasta you cooked yesterday night was really good!'"