Under an enormous white tent pitched a few hundred meters from the U.S. Capitol building in Washington, D.C., several hundred students with backgrounds in science, engineering, law, economics and architecture gathered this week at the 3rd Annual National Sustainable Design Expo.

The event is a major showcase of student ideas for an environmentally sustainable future.

The U.S. Environmental Protection Agency awards $10,000 to each college or university team with a winning idea. The teams then compete for six grand-prize awards of $75,000 each.

And these are pretty big ideas we're talking about.

In his welcoming remarks, EPA official George Gray told the students that the agency started the competition to help make the world a better place. "We also recognize how important it is to support the next generation of folks who are going to come and help us with that mission to come to support us."

The Design Expo includes projects such as methods to produce fuel from algae, an affordable system to reduce chemical leaching from farmlands and a simple means to purify water using the sun.

Environmental engineering major Kim Morris stands beside a model of a simple rope water pump. Her team from the University of New Hampshire  partnered with a non-profit organization in Niger to design and install the pump for a school garden in the West African country. "It works with animal power," she points out.

Morris is talking about camels that walk in circles to turn the wheel. "The energy," she explains carefully, "is then transferred into vertical motion, which then pulls the water out through the PVC [plastic pipe] columns located in the well. They pull up the rope and washers which then pull up the water through the column."

The water is finally transferred into a cistern and used for irrigation.

Morris says the pump not only made a difference in the daily lives of children in Niger, but also for her classmates at the University of New Hampshire. "It is exciting," she says, "to be able to transfer the knowledge that we we're learning [from] books to something that is actually usable and applicable to something so far away in Africa."

Under another part of the tent, Katherine Game from Albion College in Michigan is peddling an exercise bike hooked to an electrical generator. Game says her team's Calories to Kilowatts project  developed an on-campus education workout center. "The program is set up so that college students who use the equipment keep track of how much energy they are generating, and they can only use that much energy at the end of a month."

Game adds that students quickly learn the difference between the energy requirements of a low-wattage laptop computer and those of a high-wattage hairdryer. She notes that project surveys confirm that students are getting the message. "We've seen a significant increase in participants knowledge of renewable energy sources," she says. "And we've also seen people rate their energy-conserving behaviors. We've seen an increase of that as well in the surveys."

Other U.S. colleges have expressed interest in the Calories to Kilowatts program and Game says next year her team plans to install a unit in an elementary school in Cameroon.

"Make those muscles work!" says a father to his nine-year-old daughter, who is lifting a bar on a rope attached to a pulley that simulates wave motion on the surface of the ocean.

The project submitted by Stevens Institute of Technology demonstrates how to best harness energy from ocean waves. The device would be anchored on the sea floor and attached by cable to a buoy on ocean's surface. Engineering student and former navy diver Michael Raftery says laboratory results tell him that a scaled-up, ocean-going version could generate 100 kilowatts of power. "If we can put a few thousand units off the New Jersey coast, then we could replace things like the Ocean Creek Nuclear Power plant."

Michael Raftery contends the energy potential of wave power is enormous. "I believe that we can lead the entire world in a resource that can replace all fossil fuel and nuclear power."

Fiddle-playing Appalachian State University graduate student Jeremy Ferrell stands next to a bus that's powered by bio-diesel fuel. He and his musical teammates were among the grand prizewinners in last year's event with a project called "Closing the Bio-diesel Loop."

Given $75,000 by EPA to further develop and commercialize their idea, the students built an educational laboratory on campus that demonstrates sustainable bio-diesel production.

Ferrell explains that the closed-loop system uses renewable energy for production and recycles the by products into soap and treats the wastewater. "We really find that everybody has something to offer when it comes to bio-diesel, and that there is a lot of room for involvement."

Ferrell says the adoption of these sustainable principles makes sense for the planet and for the economy. When he graduates next month he plans to recycle his award-winning engineering talents into a job with a local Boon, North Carolina, agency that promotes earth-saving initiatives.