Social networking is huge and Facebook is the largest social networking site around with 400 million customers. And we all love it. It's a great way to keep in touch with family, friends and online "friends". It is also a great way to promote events and publicize your blog. But is it Green?

 Facebook recently announced that it will build its own data facility in Prineville, Oregon. The data centre will receive electricity from Pacific Power in Idaho which is fueled in part by coal. This has left Facebook open to criticism on the environmental front.

 Now there is a Facebook cause page to get Facebook to use 100% renewable energy. So far over 50,000 people have joined the group set up by Greenpeace International. Greenpeace is challenging Facebook to set an example and become a climate champion. (

 Data centres are enormous users of energy and with more demand around the world, IT services are expected to quadruple by 2020 enlarging their footprint, as reported by SMART 2020, a joint study by The Climate Group and the Global e-Sustainability Initiative (GeSI). About half of the energy used by data centres is to cool the computers.

 Facebook says they are building one of the most energy efficient data centres. The centre will not have mechanical cooling systems for the computers but "an innovative evaporative cooling system" says Facebook. "The efficiency we are able to achieve because of the climate of the region and the reduced energy usage that results minimizes our overall carbon footprint".

 But a new centre in Helsinki, Finland looks like it will trump Facebook's centre. The centre will be housed in a massive cave that lies underneather the Uspenski Cathedral.(The cave was used as a bomb shelter in WW II.) The captured heat will then be used to heat homes connected to the city's heating system of water-heated pipes.It will provide the equivalent of heat for 500 homes.

 The new center, built for the IT services firm Academica, promises to use half as much energy as the average data center and the company expects to save around $561,000 per year on their power bill.