PORTLAND — An experimental plant designed to convert fish wastes to fertilizer has received the blessing of the Portland City Council and could begin operations late this summer.

The council voted 6-0 Monday night to grant a processing license for the project but insisted on being kept apprised of any odors emitted from the plant.

“If people complain, we’ll get concerned,” said Thomas Valleau, director of Waterfront and Transportation.

“It’s a common sense issue, and if it’s smelly, it will be stopped,” Valleau said.

The plant, operated by the city-owned Portland Fish Exchange, would grind up fish waste — mostly heads and tails — add some acid and allow the mixture to sit for three to five days, said Dennis Frappier, general manager of the exchange.

The result, he said, would be liquid fertilizer to be sold to Maine farmers.

Processing would begin after the city obtains a zoning variance for the project, expected around the end of summer.

The project has evoked memories of the stench produced by the Pine State By-Products fish rendering plant in South Portland before it closed eight years ago. Pine State was the focus of a series of legal battles arising from odors that wafted across the harbor and into downtown Portland.

Frappier said the acid-based process to be used in the new plant on the Portland Fish Pier is far less smelly.

The National Marine Fisheries Service is providing the drum and machinery for grinding the fish and mixing in the acid, he said, and the city will provide $4,000 to set up the equipment.

The exchange’s goal is to demonstrate that the process works and that there is a market for the fertilizer, thereby inducing a commercial operator to take over and expand the plant.

The idea has been greeted with skepticism in some quarters, including Henry Gallant of Industrial Welding & Machine, a block away from the fish pier.

Gallant said fish-waste disposal is not a big problem for processors, who can sell it as lobster bait, dump it at sea or have pet food companies haul it away.