After spending a night in Central Booking, the seven protesters against a South Baltimore incinerator project who were arrested last night at Maryland Department of the Environment headquarters have been released.

The group, which includes a high school senior and a 65-year-old physician, has been charged with “trespassing at a public agency after hours” and “trespassing on private property.”

The first charge carries a maximum penalty of six months or a $1,000 fine. The maximum penalty for the second charge is 90 days or a $500 fine.

The group was part of a larger demonstration by more than 100 people protesting a trash-to-energy plant proposed by Albany-based Energy Answers International at a former chemical plant near Curtis Bay.

The seven had refused to leave the Montgomery Park building, at 1800 Washington Boulevard, until the agency would agree to cancel the permit for the incinerator, which they say expired months ago.

According to the charging documents for one member of the group, Crystal Hall, 29, the protesters had entered the first-floor lobby at about 5 p.m.

They were asked to leave by Tom French, an MDE deputy director, and Ashly Sohl, an agent of the owner of the building, identified as Washington-Monroe LLC.

Battle of Many Years

Community and environmental groups have opposed the Fairfield Renewable Energy Project for years, saying that soot, mercury and other emissions from the 160-megawatt plant would be harmful to residents’ health.

Under the state permit, the facility would be allowed to burn shredded municipal waste, tire chips, auto parts and demolition debris.

A spokeswoman Energy Answers has said emissions are within acceptable levels under the permit, and said the facility would be an economic boon to the area.

Recently, activists have pressed MDE to cancel the 2010 permit for the project, saying it expired because no substantial construction has taken place there since October 31, 2013.

Company officials have said some work has taken place onsite and were asked by MDE to document why their permit is not expired. MDE spokesman Jay Apperson said the agency is still considering their request.

Opponents say the company has had enough time.

“They are dragging their feet and MDE is letting them,” said Father Ty Hullinger, pastor of St. Anthony of Padua, St. Dominic and Most Precious Blood Churches, who participated in the protest but was not arrested.

Requiring the company to get a new permit, opponents say, is important because the requirements to obtain a permit have tightened since 2010, reflecting new thinking on the detrimental effects of small amounts of airborne pollutants.