1: Biogas Digestion

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The Sintax biogas digester adds a whole new meaning to the phrase "taking out the trash."

One person's trash is another person's treasure, or so the saying goes. But human waste as treasure? Seriously? Laugh all you want, but before too long, your hot water heater may depend on yesterday's digested lunch. In several locations around the globe, communities are already converting things like cow dung, human waste and kitchen garbage into usable energy.

If you don't focus on the stuff that goes into it, biogas digestion is actually pretty neat. It works by capturing the methane gas that gets released when waste breaks down. Usually, sewage treatment plants just vent that gas into the air, but if methane gas gets captured, it can be used for things like cooking and generating electricity.

A test project is set to start using the process in July 2009 in Vancouver, Canada. Energy company Terasen Gas will capture the gas released from a sewage treatment plant and transfer it into a nearby gas delivery pipe for the utility's consumers. Officials say the initial project will reduce greenhouse gas emissions by 551 tons (492 metric tons) a year [source: Terasen Gas]. And while what goes in may not smell so hot, the methane gas that comes out is both odorless and clean burning.

Across the ocean in India, plastics manufacturer Sintex Industries has its own version of a biogas digester available for purchase. Bacteria in the digester break down the waste you put in, and the resulting methane gets piped into the storage canister. The contraption, which looks a bit like a plastic igloo attached to a trash can, will set you back $425. If that seems like a lot just for an igloo and a trash can, remember that most igloos can't generate enough energy for a four-person family to cook all of its meals with. The digester could pay for itself in less than two years. In a south Delhi neighborhood, biogas digesters attached to public toilets provide cooking gas for a 600-student school [source: Kahn].

­Whether you opt for bugs or biogas, phones or farms, one thing is clear: With all of the alternative energies popping up, you don't have to rely on the old standbys anymore. There's no shortage of interesting (and wacky) forms of alternative energy all around us -- turn the page to learn more about a few of them.