“Saving the globe one french fry at a time,” proclaimed a sticker inside the biodiesel-fueled bus that brought a team of student inventors from New Hampshire to the Stata Center for the 2007 InvenTeams Odyssey this June. The Odyssey is a public showcase for the work of high-school inventors. Grants from the ­Lemelson-MIT program, which works to encourage young inventors, support the students’ projects.

Small changes that could lead to big energy savings were a theme at the Odyssey, where a quarter of the teams concentrated on alternative energy technologies.

“Once you get past the smell of ­diesel, you can actually smell the french fries,” said Jess Montminy, a recent graduate of Merrimack High School, standing behind her team’s idling bus. The team runs the old U.S. Air Force bus on up to 50 percent biodiesel and plans to test-run it on 100 percent bio­diesel this fall. The students built a processor that produces biodiesel from used fry oil, methanol, and a hydroxide base. The processor’s battery will eventually be solar powered. The students have further reduced the bus’s impact on the environment by making small adjustments, such as removing a fuel-­hogging AC unit.

The team from Divine Child High School in Dearborn, MI, designed a system that converts a bicyclist’s ­muscle power into battery power for devices with USB capability. The students had fun with the design process. Jeff Brookins, a recent Divine Child graduate, said they bought an Insignia MP3 player with the full warranty in case they blew it out. By the time they got to the Odyssey, however, their confidence had grown: recent graduate C. J. Demmer used his personal iPod to demonstrate the system.

Pedaling furiously on a bicycle in a stand, Demmer stopped only to gulp down glasses of water. Cords sprouting from the bicycle’s frame were connected to a laptop on a nearby table. “I’ve already charged my iPod and my cell phone,” he said. “What’s next?”