No one warned me that becoming a parent would make me the biggest consumer of batteries on earth. Swings, bouncy seats, music-playing mobiles and monitors all require disposable batteries and use them up with astounding speed. That's on top of the other things in the house, like flashlights, remote controls, a wireless keyboard and mouse and so on, that need batteries. All told, I find myself in Radio Shack ( RSH) almost monthly to get 12-packs of AAA and AA batteries. And we haven't even entered the stage of battery-powered toys yet. According to the GreenYour ... Web site, Americans buy some 3 billion batteries a year, or 32 per household. About two-thirds of these wind up in the trash, where cadmium, nickel and lead can leach from landfills into groundwater or be released into the air and water during incineration. Those stats are enough to make me feel a twinge of guilt with every oscillation of my daughter's swing and click of my mouse. A few baby items, like the monitors, can be battery-operated or plugged in, which made me wonder about the relative cost and environmental impact of these respective power sources. It also made me wonder about rechargeable batteries. Colton Dirksen, co-founder and environmental director of Ecomii, a Web site that offers environmental advice on household issues such as battery use, says plugging in is "hands down the way to go." First, batteries have to be manufactured and packaged, and that wrapping goes into the landfill alongside the batteries. The packages are shipped to the store and you need to drive to the store to get them. And then there is the issue of all those toxic metals that seldom get recycled.