London Olympics' green efforts were showed to UN officials and journalists on Thursday, which was commented as "already evident" by Achim Steiner, Executive Director of UN Environment Programme (UNEP).

The?Olympic Park in London. [Xinhua file photo]

Though the Olympic Park is still under construction, its green infrastructure was announced as complete by organizers. A key point is the Energy Center is now fully operational, which has a three megawatt biomass boiler and is around 30 percent more efficient than traditional heat and power generation methods.

Wind turbines could also be seen on the site, as well as lots of reusable structures, in a tour led by David Stubbs, Head of Sustainability at London Organizing Committee of Olympic Games.

He presented the visitors a Pre-Games Sustainability Report, which listed six priorities as: carbon management, zero waste Games, sustainable and accessible transport solutions, economic benefits of sustainability, promote sustainable living, and Olympic park legacy.

It is said carbon footprint of the Olympic Park is on track to achieve a target of reducing 50 percent emissions, compared with estimation in 2006 when construction started.

"They have made in London the environment sustainability a consideration in many different aspects," said the UNEP chief Achim Steiner, after visiting the Olympic Park on Thursday.

He told Xinhua that though we have to wait after the Games to assess how well those measures work, "I think for London, the legacy value of this Olympic Games is already evident."

Steiner said UNEP is working with the International Olympic Committee to develop a set of measurements which might be used to judge the environmental performance of Olympic Games in future.

"The issue of environment sustainability has become an increasingly important criteria in the bidding process (of Olympic Games)," he said, praising that as "a positive development."