Worldwide, 15 billion disposable batteries are born each year. When they die, they mostly end up in landfills, where toxic mercury and heavy metals leach into soil and water. Battery makers are trying to do better–by reducing heavy metal content and figuring out how to recycle it. But according to Shelley Minteer, a battery specialist and electrochemist at St. Louis University in Missouri, "the technology is advancing at a snail's pace." While many towns have instituted "Hazardous Waste" days when you can drop off dead soldiers, experts say that rechargeables are the best solution now. Here's a quick primer on the most common types:
NiMH (nickel metal hydride) batteries have no toxic ingredients and last three to four times longer than alkalines. They work well in cold weather and come in a multitude of sizes. That said, they're more expensive than alkalines (about $8 for four AAs at all-batteries.com, not including shipping or the charging unit), they discharge quickly when not in use, and they lose staying power with each recharge.
NiCD (nickel cadmium) rechargeables are becoming obsolete due to their relatively poor performance, highly toxic cadmium, and inconvenient disposal requirements (you must dispose of them via the manufacturer or a specially equipped recycling center).
Zinc air batteries are non-toxic and are widely used in hearing aids. While they only come in coin-size configurations, they work in some watches and mini-lights, and Minteer says new shapes may come soon. Since this technology requires airholes in the device, zinc batteries aren't the choice for weather-exposed applications.
Lithium ion rechargeables are ideal for backpackers because they're small, light, long-lasting (up to 300% longer than alkalines), high voltage, and hold a charge for a long time. Downsides: They're pricey–four AAs cost about $30 on sale at all-batteries.com, not including shipping.
What's next? Minteer and others say there's a new type of battery in development that promises to be the greenest of them all. In three to five years, watch for one that runs on sugar-eating microorganisms and comes in a variety of configurations to power everything from a GPS to a computer. For more info, visit greenbatteries.com or earth911.org.