WINDHAM — A massive greenhouse project proposed for land off Route 302 would occupy the space of seven Walmarts and could cost more than the proposal for The Forefront development on Thompson’s Point in Portland.

John der Kinderen of Arundel is proposing to build 37 acres of greenhouses for a new company called Sebago Farms that would raise hydroponic vegetables and fish to sell to food distributors throughout the Northeast.

Der Kinderen hopes to start construction this spring, begin operations by the end of the year, and have it completely up and running in 2013. Der Kinderen has been working on the plan with Windham officials, and Planning Board member James Hanscom said the board could hold extra meetings to expedite the permitting process.

The business, which would employ 170 people, would be Windham’s biggest taxpayer and one of the largest developments in the state, said Tom Bartell, the town’s economic development director.

“This is big,” he said Monday, after a brief review of the project’s sketch plan by the Planning Board.

Sebago Farms is the first venture of WNWN LLC, owned by der Kinderen, who said he is retired but would not comment Monday on his previous work or business experience.

Der Kinderen also declined to put a price tag on the project. However, Bartell said it would probably compare to the $105 million mixed-use project planned for Thompson’s Point in Portland, which would include a concert hall, sports arena, hotel space and other amenities.

“This very well could be more than that,” Bartell said.

Der Kinderen said that WNWN is working with BioSynEnergy, a worldwide green technology company with corporate offices in Pennsylvania.

He described the project as “high-tech” and “very low-impact.”

The greenhouses would be powered by natural gas engines, and waste from its operations would be processed by a bioreactor and turned into fertilizer, der Kinderen told the Planning Board.

The 73-acre site of the proposed project is the Quarry Ridge Business Park off Route 302 in Windham, just north of the town’s busiest commercial corridor. WNWN, which plans to buy that land from R.J. Grondin & Sons, considered about a dozen other sites in southern Maine before deciding on the Windham location, der Kinderen said.

In addition to creating jobs and paying taxes, the new business would likely draw more companies to the business park and beyond, said Larry Eliason, vice president of the Windham Economic Development Corp.

“This is going to attract other investment to the area and act as an economic engine for business,” he said.

The sketch plan calls for three greenhouses that would collectively cover 1.6 million square feet, which Bartell said is about the size of seven Walmart Supercenters.

The largest greenhouse would be 2,000 feet long — nearly four-tenths of a mile — and used to grow “microgreens,” a type of lettuce. Another hydroponic greenhouse would grow tomatoes, peppers and possibly herbs, der Kinderen said. The smallest greenhouse would have 48 pools where coldwater fish, such as arctic char or steelhead trout, would be raised.

Der Kinderen said the closest comparable facility, with both agriculture and aquaculture, is in Nova Scotia. He said Backyard Farms in Madison, which grows tomatoes in greenhouses, would be a competitor, but added that there’s plenty of room in the market.

“There’s a very high demand for this product,” der Kinderen said.

Staff Writer Leslie Bridgers can be contacted at: 791-6364 or at [email protected]