What to do with heat produced by data centres?

Suppose we combined all the data centres in the world as one country. It might be a shock that they would be the fifth-largest consumer of energy in the world. These data centres account for approximately 2% of greenhouse gas emissions, almost the equivalent of the entire global airline industry.

There are a number of innovative examples of people using the energy by-products in innovative ways, like this story from Denmark covered by the BBC.