Stephanie Ferri and Anna Shapiro, both of Providence, work in this this tractor-trailer that has been retrofitted as a greenhouse for hydroponics and has served as an urban agricultural lab.

The Providence Journal / Bob Thayer

A unique greenhouse on wheels, a laboratory for ideas started by a collective of artists several years ago in Providence, has gotten a new lease on life.

The “urban agricultural unit,” or UAU, is a 35-foot tractor-trailer retrofitted with polycarbonate panels like those used in conventional greenhouses to let in the sun.

Now the New England Grassroots Environmental Fund has awarded the stewards of the mobile greenhouse $1,000 in seed money to try to make the unit self-sufficient in its energy and water needs, key elements to its long-term viability.

For much of its life, the UAU has brought hydroponic herbs and vegetables to an urban brownfield, the Steel Yard. in the industrial Valley Street section of Providence.

Originally, the creator of the UAU hoped to turn a profit from hydroponic crops. Nick Halmos, who came to Providence as a student at Brown University nearly a decade ago, gathered support for the project through his participation in a collaborative of artists based at the Steel Yard.

But the mobile greenhouse has evolved into a focal point for innovation among a fluid cast of people passionate about the arts and the environment who say they want to improve the quality of urban life.

If the prototype can become self-sustaining, the greenhouse-in-a-trailer is “something we want to replicate” to serve urban areas with contaminated soil or disaster areas like post-Katrina New Orleans, said Anna Shapiro, one of the key stewards of the project.

On one level, the mobile greenhouse represents a meeting of spontaneous energy and creativity that is its own reward.

“The UAU is fun,” said Shapiro, an artist familiar with the Steel Yard who had had peripheral interest in the mobile greenhouse until three years ago, when it became apparent the project needed new leadership.

Shapiro learned all about hydroponics from Stephanie Ferri, who has grown plants without soil as a hobby for about 15 years. Ferri, a muralist and painting contractor, and Shapiro met through a mutual acquaintance and have become fast friends while supporting the UAU.

In all, about 75 people have supported the project since its inception in 2004, with about two dozen now active, according to Shapiro. A freestanding wooden staircase, painted purple, leads to the trailer, which encloses a small oasis of hydroponic basil and cucumbers.

Earlier this year, Shapiro planted the seeds in pots filled with volcanic rock, which stands out for its capacity to absorb water.

She put the pots in waist-high “beds” made of PVC pipe. A homemade irrigation system, a combination of PVC pipe and tubing, carries nutrient-rich water from an adjacent tank through the inside of the beds, where the liquid is released in a mist and the volcanic rocks suck it up, nourishing the plants.

For about five years, the UAU had been a fixture at the Steel Yard at 27 Sims Ave. Now the UAU is moving to Seven Arrows Farm in Attleboro, where owner Michel Marcellot, an experienced hand at greenhouses, will help with the effort to make it self-sufficient for energy.

gmacris@projo.com