The promise has been kept. Facebook's engineers have been working for years to improve the energy efficiency of their data centres, so much so that Greenpeace, in its latest report "Who is Winning the Race to Build a Green Internet", places the social network at the top of the rankings for renewable energy use across its systems. The list is now growing longer with the announcement of the opening of a third European data centre, which will be built in Denmark, following those based in Sweden and Ireland. And it will run entirely on renewables.

"The Odense data centre will be one of the most advanced and efficient in the world", said Niall McEntegart, director of data centre operations at Facebook. The new facility will indeed be built in the city that gave birth to the writer Hans Christian Andersen and, once operational, will create jobs for 150 people. The building will be fully operational in 2020 and will be powered by renewable energy produced in Denmark, largely from wind.

Facebook powered by green energy

The decision by the group founded by Mark Zuckerberg to choose Denmark as the location for one of their data centres also has the support of the Danish Ministry of Energy, which commented: "We have one of the energy systems with the largest share of green energy in the world, a high level of supply security, good fibre optic connectivity and competitive prices." Fertile ground for a company that works on the web.

Facebook has long been working on increasingly efficient data centres. Some years ago, the company's engineers designed and built a new data centre that was 38 per cent more efficient and 24 per cent cheaper than traditional ones, making the project public under the name Open Compute Project. "Since we began using the Open Compute Project in our data centres," reads the official Facebook sustainability page, "we estimate we have saved enough electricity to power approximately 127,000 homes for a year and to avoid greenhouse gas emissions equivalent to taking nearly 136,000 cars off the road for a year."