Google's energy use became the subject of scrutiny in 2009 following the Gurdian's story claiming that each search carried out on the website had a carbon footprint of 7g of CO2 - around half as much as boiling the water for a cup of coffee. Google's response at the time was that this "figure included many factors it was not responsible for, such as the power consumed by the user's computer, and that its share of the footprint was only 0.2g of CO2 per search."
Google's September 8 announcement repeats the 0.2g figure and gives equivalent numbers for other Google services, such as YouTube (1g of CO2 for each 10 minutes of viewing) and Gmail (1.2kg of CO2 per year for the typical user).
Google estimates that data centres account for around 1% of the world's electricity use, and that Google itself consumes around 1% of that amount.
Almost one-third of the company's electricity comes from renewable sources - a figure that is continuing to rise. The company offsets the emissions generated by the remainder of its electricity supply, along with those from its offices and transport.
"A carbon offset represents a reduction in greenhouse gas emissions. A developer can create a carbon offset when she builds a project that lowers greenhouse gas emissions. Revenue from the sale of the offset finances the installation of the project."
The anatomy of a carbon offset
Google says we are "investing hundreds of millions of dollars in renewable energy projects and companies, we're helping to create 1.7 GW of renewable power. That's the same amount of energy used to power over 350,000 homes, and far more than what our operations consume."
Google posted a video embedded below, that "provides a window into how they evaluate projects, showing two examples of the types of projects we buy," stated Jolanka Nickerman, Program Manager, Carbon Offsets Team.
Nickerman noted the "first project is located at the St. Landry Parish landfill in Louisiana. This landfill is a perfect example of how big reductions in greenhouse gas emissions can pop up in some out-of-the-way places. (As my little brother likes to say, I am in the business of "dump investigations.") We then visit a project at a hog farm in North Carolina. Both of these projects reduce greenhouse gas emissions by capturing and destroying methane, a potent greenhouse gas."
If you want to learn more about how we evaluate carbon offsets and apply them to our carbon footprint, check out this white paper:
Google Carbon Offsets whitepaper (read only):