<p><strong>Curved and cedar-clad, the Velodrome could be the star sustainability attraction of the 2012 London Olympic Games. Not only was the lovely $147 million structure built on schedule and on budget, but it is the most energy-efficient venue in Olympic Park.</strong></p><p>That's important because while the athletes converging on England's capital this fortnight go for gold, organizers had green in mind when they planned out how to power these games. From the start, when Britain made its successful bid in 2005 to host this year's games, it placed environmental sustainability at the core of its campaign. It even agreed to allow an outside organization, the <a href="http://www.cslondon.org/">Commission for a Sustainable London 2012</a> (CSL), to monitor its efforts.</p><p>Neither the commission nor the games' myriad unofficial judges have given the performance a perfect ten. The CSL is concerned that waste won't be properly segregated for recycling or reuse. And critics have complained about the influence and role of corporate sponsors.</p><p>But there's no question that organizers have cleared some high hurdles in their effort for a more sustainable Olympic Games.</p><p>Case in point: A plan for a wind turbine to provide nearly 10 percent of the site's energy had to be scrapped for safety and commercial reasons.</p><p>Still, the organizers will achieve their goal of reducing carbon emissions—mainly through conservation measures. The Velodrome is a prime example.</p><p>Because its concave roof resembles a processed potato chip, Londoners have nicknamed the building The Pringle. But there's no fat inside. The fastest cycling track in the world will be 31 percent more energy efficient than required under the 2006 building regulations in place at the time construction was planned.</p><p>(Related: "<a href="http://news.nationalgeographic.com/news/energy/2010/12/photogalleries/101214-green-government-buildings/">Pictures: Seven Supergreen U.S. Government Buildings</a>")</p><p>Achievements like the Velodrome and London's efforts to stage the first public-transit-centered Olympic Games have earned the organizers positive marks on sustainability.</p><p>"Overall, this has been a great success," the CSL concluded in its <a href="http://www.cslondon.org/wp-content/uploads/downloads/2012/06/CSL_Annual_Review_20111.pdf">final report </a>in June. But the most important measure, the commission said, will be how much London 2012 influences sustainable practices beyond the games.</p><p>(Related interactive: <a href="http://environment.nationalgeographic.com/environment/energy/great-energy-challenge/world-electricity-mix/">Global Electricity Mix</a>)</p><p>—<em>Thomas K. Grose in London</em></p>

Velodrome: Chipping Energy Use

Curved and cedar-clad, the Velodrome could be the star sustainability attraction of the 2012 London Olympic Games. Not only was the lovely $147 million structure built on schedule and on budget, but it is the most energy-efficient venue in Olympic Park.

That's important because while the athletes converging on England's capital this fortnight go for gold, organizers had green in mind when they planned out how to power these games. From the start, when Britain made its successful bid in 2005 to host this year's games, it placed environmental sustainability at the core of its campaign. It even agreed to allow an outside organization, the Commission for a Sustainable London 2012 (CSL), to monitor its efforts.

Neither the commission nor the games' myriad unofficial judges have given the performance a perfect ten. The CSL is concerned that waste won't be properly segregated for recycling or reuse. And critics have complained about the influence and role of corporate sponsors.

But there's no question that organizers have cleared some high hurdles in their effort for a more sustainable Olympic Games.

Case in point: A plan for a wind turbine to provide nearly 10 percent of the site's energy had to be scrapped for safety and commercial reasons.

Still, the organizers will achieve their goal of reducing carbon emissions—mainly through conservation measures. The Velodrome is a prime example.

Because its concave roof resembles a processed potato chip, Londoners have nicknamed the building The Pringle. But there's no fat inside. The fastest cycling track in the world will be 31 percent more energy efficient than required under the 2006 building regulations in place at the time construction was planned.

(Related: "Pictures: Seven Supergreen U.S. Government Buildings")

Achievements like the Velodrome and London's efforts to stage the first public-transit-centered Olympic Games have earned the organizers positive marks on sustainability.

"Overall, this has been a great success," the CSL concluded in its final report in June. But the most important measure, the commission said, will be how much London 2012 influences sustainable practices beyond the games.

(Related interactive: Global Electricity Mix)

Thomas K. Grose in London

Photograph by Edmund Sumner, View/Corbis

Pictures: London Leaps Hurdles in Green Olympic Games Bid

Organizers for the London Olympics have made significant strides toward more energy-efficient summer games, but some of their efforts didn't make it to the finish line.

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