Using models built from bottles and broken toys, middle school students from Louisiana and Mississippi did their best on Saturday to convince judges of a concept still well in the future — creating a self-sustaining city that relies on renewable resources.

Students presented their visions to a panel of judges at LSU as part of the regional finals for Shell’s “Future City Competition.” The winning team from each region heads to Washington, D.C. for a national competition in early February.

Saturday’s event “helps these little kids put perspective not only (with) the problems that we’re facing but … how you go about putting together solutions,” said Southeastern Louisiana University Professor Cris Koutsougeras, who is also a judge and used to coordinate the Future City Competition.

The presentations from the four participating schools were wide-ranging. Students from St. Thomas More Catholic School in Baton Rouge presented Haban, their dream city of 100,000 people who would be living on the coast of Namibia.

Their city would run on underwater turbines turning so slowly that sea creatures could pass through the turbine’s blades unharmed. Energy and other resources would be transported through tiny tubes — “nanotubes” — built into roads. There would also be “fog towers” to collect water from fog, and hydrogen-powered “hover buses” with polarized magnets to prevent them crashing into each other. The primary food source would be soybeans.

The team used motors from broken toys to piece together their diorama, which was filled with motorized parts like miniature wind turbines.

Despite all these ideas, member Judy Vu, 13, laughed nervously when she told the audience, “The most challenging thing was memorizing our lines.”

Then, students at Scotlandville Pre-Engineering Magnet Academy presented AquaCropolis, a city as large as the state of Rhode Island but based on a coastline in Southeast Asia. AquaCropolis featured a floating vertical farm that runs on nutrient-infused water instead of soil, and positions itself automatically towards the sun.

To fit all of the city’s components, AquaCropolis grows its food offshore. There are giant “aquapods,” or underwater cages for breeding Blue Fin and Ahi Tuna fish.

Team members added that a sizable chunk of the city’s income is from tourism. Their diorama was built from found materials like Gatorade and shampoo bottles.

“Our city has a lot of colors to it,” said 12-year-old team member Deylen Colligan, who played the role of mayor during the team’s presentation.

Two teams from Colmer Middle School in Pascagoula, Mississippi, also competed. Each featured ways to build a life after escaping from a cataclysmic threat.

There was “Aquaphena,” an entirely underwater city off the coast of Hawaii that sits just beneath the surface, with corn crops growing above the water and into the air. Residents would get around by elevator, and 50 percent of the city’s jobs would come from purifying air and water.

The city was designed to be difficult to find if China started war with the United States to collect their massive unpaid dues that so far have gone unpaid, said team member Cameron Wells, 13.

The other Mississippi team presented “AstroCity,” a Mars outpost with multi-layered glass dome that replicated conditions on Earth where 70,000 residents could grow chicken and potatoes.

As part of the contest, students had to submit an essay about how their city would work, and even a digital model of a sustainable city they produced in the SimCity videogame.

The benchmarks are high.

The city must make money and the energy sources have to be renewable, but approval ratings from the virtual residents must also weigh in at 80 percent, said Jesse Ardonne, a volunteer judge and PhD student in electrical engineering at LSU.

“Not everyone met it,” Ardonne said with a laugh, “It’s very hard to satisfy everyone.”

Follow Daniel Bethencourt on Twitter: @_dbethencourt.