In a little over two decades cell phone batteries have shrunk from the size of a brick to the size of a credit card; laptop batteries have become lighter and more powerful, and we could soon even be using paper thin batteries in out electronics – but it seems little has changed when it comes to disposable batteries.

Despite the marketing claims that they go on and on, AA’s still seem to have a knack of running out of juice at the worst possible moment (like when you grab a torch during a power outage), and it is estimated that each year in the US over two billion batteries are disposed of in the trash, posing a huge potential threat to the environment – but now, at least, there are other options.

In Japan an emergency water powered rechargeable AA battery is now on the market. The NoPoPo (non-pollution power) aqua batteries can be recharged three to five times by filling them with any available liquid, including water, beer, saliva, and even urine. The batteries, which don’t contain any harmful chemicals, can power a small handheld torch for up to 20 hours, and as they don’t deteriorate like conventional batteries, they can potentially keep their charge for up to ten years, making them an ideal emergency battery for remote locations. The aqua batteries are only on sale in Japan currently, but may be on sale in the US in 2008.

For anyone who spends a lot of time on the computer, however, USB-cell batteries may be a better option. These AA rechargeable batteries plug into any USB port to recharge, and can then be used in any electronic product that uses standard batteries. The batteries, produced by a UK company, are currently only available as AA size, but AAA and cell phone batteries are also in development.