WESTBROOK – Smiling Hill Farm in Westbrook is known for its dairy products. But now the farm on County Road also hopes to make a name for itself as a producer of fresh tomatoes grown year-round in a 20-acre greenhouse.

The hydroponic vine-cluster tomatoes Smiling Hill would grow would be red and ripe when they left the greenhouse to go to customers in Maine and places like Boston and New York. But they would be “green” in the sense that they would be grown in an environmentally friendly way, according to Warren Knight, president of Smiling Hill.

The hope is that thermal waste energy from nearby Calpine Corp.’s Westbrook Energy Center could be used to help heat the greenhouse, he said. Also, he said, he hopes that carbon dioxide emissions from the power plant on Eisenhower Drive could be used to help enhance growth of the tomatoes.

Knight said that the proposal for the greenhouse, which he said would cost $20 million or more to build, is still in the conceptual phase, though the project may be ready to go before the city for approval this fall. And Knight said the greenhouse would not only be good for the local economy — creating about 100 jobs – but for the environment, as well.

He said the state-of-the-art greenhouse would take two waste products “and utilize them to make another product.” He said the product would be “what I call ‘green’ tomatoes.”

Knight’s partner in the project, Larry Gianatti Sr., president of Quality Sales Inc., a produce wholesaler/distributor in Hartford, Conn., said, “Our goal is to make this a totally green project.”

In addition to getting energy from Calpine, Knight said, other green aspects of the project include a plan to capture the rainwater that falls on the roof of the greenhouse and use it to water the tomato plants.

Also, Gianatti said, large amounts of fossil fuel energy currently are required during the winter to import tomatoes to New England from countries such as Mexico, Spain and Israel.

But fresh, ripe tomatoes grown all year in Westbrook only a few hours from markets like Boston and New York would require much less energy to transport, Gianatti said.

Norma Dunn, a spokeswoman for Calpine, said that the greenhouse “sounds like an exciting project and we look forward to exploring whether there is a role for our Westbrook facility. As always, we welcome the opportunity to work with businesses where our plants can add additional value to the community.”

Their greenhouse proposal is still in the idea phase, but Knight and Gianatti say there’s evidence it can work.

That’s because a company called Backyard Farms in Madison, founded in 2005, grows hydroponic tomatoes in 42 acres of greenhouses in the community.

Gianatti said that Backyard Farms was “instrumental in showing that a greenhouse product could successfully grow in Maine year-round.”

When asked if there would be a market for more greenhouse tomatoes in addition to those grown by Backyard Farms, Gianatti, whose company specializes in tomatoes, said that vine-cluster tomatoes and specialty greenhouse tomatoes are “in great demand.”

Knight and Gianatti have talked with state and local officials about their proposal. It’s generating positive interest.

John Kerry, director of the governor’s office of Energy Independence & Security, said, “I think the concept is a solid concept and it fits well within the parameters of the state’s energy policy.”

In addition to being energy efficient and reducing greenhouse gases, he said, the project would create jobs and grow Maine-based produce. Kerry said the state would “do what we can to enhance its development.”

Both Westbrook City Administrator Jerre Bryant and Keith Luke, the city’s director of economic and community development, called the project “exciting.”

Luke said, “I think that it’s a project that has some real legs to it.”

And Bryant said, “The city is very excited about this project.”

It would be a permitted use in the industrial zone where it’s located, but may need site plan review, Bryant said.

Knight said that the greenhouse would be located on farmland that Smiling Hill owns across from the Calpine plant.

He said it’s not certain yet how large the greenhouse would be to fit on that site but the estimated size is between 18 acres to 24 acres, he said. It would cost about $1 million per acre to build, Knight said.

He said the greenhouse would be illuminated inside at night to help the plants grow. Usually, the greenhouse would be covered by thermal blankets at night to keep the heat inside, but would need to be uncovered on winter nights when there’s ice or snow, Knight said.

But he said the light emanating from the greenhouse on such nights would not appear greater for most people who might see it in Gorham and elsewhere than the glow they already see from the city of Portland.

The jobs the greenhouse would create range from tomato pickers and groomers to technicians, mechanics and a plant manager, Knight said. He said some would be salaried positions and he characterized the picking and grooming jobs as skilled, “medium-wage” positions.

He said the tomato plants grow 20-feet to 30-feet high and those picking fruit and grooming the plants to remove dead leaves would need to use scissors lifts for those jobs.

Knight and Luke said that the influx of workers there may lead to public bus service to that area of the city.

Depending on such factors as approval from the city and the Maine Department of Environmental Protection, Knight said the goal is for the construction of the greenhouse to start in May 2011 or May 2012. It must be built in the warm months, so it can be glassed over before the winter arrives.

He said that greenhouse would only be the first phase of the project. The plan is also to win approval for a second greenhouse to be built on some adjacent wooded land a few years later and perhaps for a third greenhouse, Knight said.

The greenhouse proposal is one reason that Smiling Hill has concerns about Pike Industries being allowed to continue blasting at its quarry on Spring Street. The city is currently talking with Pike about an agreement to let the company continue restricted operations at the quarry in exchange for Pike’s dropping a lawsuit against the city over operations there. Knight said he’s worried about shock waves and pebbles from blasting hitting the greenhouse.

Gianatti said the way that the tomatoes will be grown in the greenhouse is the way more and more types of produce will be grown in the 21st century.

“Hydroponic in a safe, clean environment is the wave of the future,” he said.