Outside the Sustainability Workshop at the Navy Yard in Philadelphia, high school senior Anissa Rementer is standing by the open doors of a gray shipping container.

Its cargo is a raised platform bathed in purple light.

A steady stream of nutrient-infused water flows through the platform. On top, dozens of little lettuce plants reach for the LED panels above. The whole thing is powered by a few nearby solar panels.

"This is the hydroponic system," says Rementer. She and three other Sustainability Workshop students designed and built it.

It's called "Greens-In-A-Box."

"Seed money"

The hydroponic system and its fledgling lettuce plants are the fruits of a $10,000 grant from FreshDirect. The online grocer is calling the initiative its Green Angel Fund Challenge.

Company representatives were in Philadelphia Monday to present a giant check.

"I would think of this more like — no pun intended — seed money," said John Leeman, FreshDirect's chief marketing officer.

The idea is to test out new ideas for sustainable urban agriculture, while getting high school students excited about growing food.

Leeman says the company could potentially broker connections between the student teams and its network of produce suppliers. He says FreshDirect, which operates in greater New York City and greater Philadelphia, has over 100,000 active customers.

"As a company committed to both urban dwellers and farmers, we feel it's our responsibility to help ensure a sustainable and healthy supply chain of food — for all consumers," FreshDirect co-founder David McInerney said in a statement. "We can't wait to see the approach these students take to introduce sustainable farming methods that will ultimately lead to a healthier world."

Philly vs. NYC

FreshDirect is turning to both Philadelphia's Sustainability Workshop and New York City's John V. Lindsay Wildcat Academy in the Bronx. The two schools both place a strong emphasis on project-based, hands-on learning.

The company is pitting the schools against each other in a friendly competition. Next month, the two teams will be graded on the quantity of their greens and the quality of their eco-friendly setups.

"Competition motivates people — teachers and students," said Sustainability Workshop co-founder Simon Hauger. "And it's a fun twist on the whole thing."

The no-stakes showdown has the endorsement of both Philadelphia Mayor Michael Nutter and New York Mayor Michael Bloomberg. The mayors are set to proclaim June 11 as "Urban Farm Education Day." That's the day the winner of the Green Angel Fund Challenge will be crowned.

On Monday, the four members of team "Greens-In-A-Box" were confident that they would out-green their counterparts in the Bronx.

They still have a greenhouse to add to the shipping container's roof.

Whatever the outcome, Sustainability Workshop student Anissa Rementer seemed pleased with a new skill set. Before "Greens-In-A-Box" she had never farmed before.

"I wasn't really interested until now," Rementer said. "I actually like it. I like growing my own things and knowing that I grew it."