Q. Dear Twig: You talked about electric cars. What other ways can you run a car?
A. Well, you can push it yourself. Ha ha ha! Kidding. ["Not funny": Twig's niece Elderberria.] OK, here are some of the other ways:
Biodiesel: Liquid fuel made from vegetable oils and animal fats. Renewable.
Ethanol: Liquid fuel made from starch crops such as corn. Renewable.
Natural gas: Either compressed (as a gas) or liquified (into a liquid). Non-renewable. Pollutes less than gasoline.
Hydrogen fuel cell: Hydrogen goes in the fuel tank, which fuels the fuel cell, which makes electricity, which runs the car. Only "exhaust"? Water. Earth has lots of hydrogen.
Propane: Liquified petroleum gas. Pollutes less than gasoline. Plus makes for cheaper vehicle upkeep.
Note: They all work only in special cars. That is, you can't just pump French-fry-oil biodiesel into your dad's Pinto and expect it to run. Urps!
P.S. All these fuels are in many different stages of use and development. Mmm, French-fry fuel ...
Notes: Check out, for starters, the Web site of the U.S. Department of Energy's Alternative Fuels and Advanced Vehicles Data Center, http://www.eere.energy.gov/afdc/vehicles/electric.html. Other alternative vehicle fuels include solar energy (http://engineering.osu.edu/studentprojects/solar.php); compressed air (http://freeenergynews.com/Directory/CompressedAir/index.html), and hay/oats fuel cell (http://content.cdlib.org/ark:/13030/kt3v19q1fn/).
"Smart Stuff with Twig Walkingstick," published by The Ohio State University College of Food, Agricultural, and Environmental Sciences — specifically, by the Ohio Agricultural Research and Development Center (OARDC) and Ohio State University Extension, the research and outreach arms, respectively, of the College — is a weekly column for children about science, nature, farming and the environment. It's written at a 4th-grade reading level. For details, to ask Twig a question, and/or to receive the column free by mail or e-mail, contact Kurt Knebusch, CommTech, OSU/OARDC,1680 Madison Ave., Wooster, OH 44691, email@example.com, (330) 263-3776. Online at http://extension.osu.edu/~news/archive.php?series=science.