We use a lot of batteries. They don't create carbon emissions when inserted into a walkie-talkie or a digital camera. I'm sure parts of the battery's shipping, production and recycling processes release carbon emissions, but their actual use does not. The greenest part of a battery's life is when they are in your hands, being used for their intended purposes. That means it is your responsibility to keep them alive as long as possible before sending them to the recyclers. Here are some tips.
1. Buy Rechargeable
Painfully, painfully obvious. But a good place to start. Buy rechargeable batteries for obvious reasons. Nickel Metal Hydride (NiMH) are better than rechargeable alkaline batteries. NiMHs can be charged thousands of times before they need to be disposed of. If you are not going to recharge, then buy alkaline batteries. They maintain their power longer than NiMH batteries. NiMH's are terrible if you don't plan on recharging them.