Server farms are known to be very energy consuming. A common server uses up hundreds of watts of electricity, and runs on a 24/7 schedule. Luckily, some companies have decided to minimize their impact on our planet by utilizing renewable energy sources as their main power supplies. A webhosting company powering its servers by Solar or Wind energy can spare the world from quite a bit of unnecessary CO2 emissions. It may not be an astronomical contribution, but it's another step in the right direction.
I'm going to recommend you a webhosting company that does exactly that.
(You sure can remove my affiliate ID from the URL if you like, but I would appreciate it if you didn't :)
So at least check it out. I guess what they're doing is worth a click: