Mike Ross wants to deputize meter maids to enforce the city's anti-idling ordinance.
Dan Conley says Boston should finance solar panels on houses and businesses, with owners paying the city back through their property tax bills over time.
And Rob Consalvo wants the city to be carbon neutral by 2050.
These were among the proposals issued Tuesday afternoon at a mayoral forum at Suffolk University Law School focused on environmental issues.
The panel, convened by 30 environmental groups and leaders, was designed to elevate climate change, public transit and other green issues in the city's first competitive mayor's race in a generation.
Current Mayor Thomas Menino "has done a lot to put Boston on the map as a green city," said Tom McShane, former president of the Massachusetts League of Environmental Voters and a co-sponsor of the forum. "And we didn't want to lose that."
The forum, #bostongreenmayor, drew nine of the 12 candidates — all of them seated side-by-side at a long table in a small auditorium.
The sheer volume of candidates has made it difficult, in recent weeks, to wrangle substantive discussions at mayoral forums.
But organizers provided candidates with briefings and a list of questions in advance in a bid to raise the bar. And the forum did not lack for ideas.
The candidates, though, were generally united in their assessment of the big environmental challenges facing the city — rising seas, subways that don't run late enough and streets that aren't as bicycle-friendly as they should be.
Indeed, the chief competition focused on who could set the boldest goals for the city.
Consalvo, a city councilor, pitched his carbon-neutral city idea; Conley, the Suffolk County district attorney, said he wants to double the city's 2020 goal for solar energy to 50 megawatts; and City Councilor John Connolly declared he will quadruple it.
The candidates also used the forum to hit on broader campaign themes. City Councilor Felix Arroyo, a former union organizer, said "nothing calls for an organizing mindset like the environment — it requires us all to buy in."
John Barros, who has emphasized inclusion of lower-income communities in civic life, said it was "environmental justice" issues that brought him to activism as a teenager.
And Charlotte Golar Richie, a former aide to Menino who has sounded similar themes, said every neighborhood should have the sort of tree canopy that hangs over West Roxbury.
Conley's call for city financing of solar panels — repaid over time through special assessments on property tax bills — is designed to get around a significant obstacle to widespread adoption by businesses and homeowners: the upfront cost of buying and installing is often prohibitive.
Thirty states, including Massachusetts, have passed laws allowing for what is known as Property Assessed Clean Energy (PACE) financing.
But the idea is just starting to get off the ground. And it is mostly business owners — not the homeowners originally targeted — who have made use of PACE to date.
A major impediment: the Federal Housing Finance Agency, which handles the financing of about two in three new residential mortgages through Fannie Mae and Freddie Mac, will not allow those agencies to buy mortgages for properties encumbered with PACE liens.
Repayment of those liens often take priority over repayment of the mortgages during foreclosure — providing an unacceptable risk for housing agencies that came under fire during the housing crisis.
Conley spokesman Mike Sherry said he would design the city's program to alleviate federal concerns and ensure that homeowners, as well as business owners, could make use of it.
Conley also pitched a plan to cut down on air pollution emanating from Boston Harbor. Modeled on a program in Los Angeles, it would give ship owners incentives to use low-sulfur fuels when entering or leaving the harbor, among other things.
Connolly said he'd pilot a "pay as you throw" program in one Boston neighborhood. After the forum, he said that neighborhood would be Jamaica Plain.
"Pay as you throw" often refers to a program that charges for garbage pickup by volume, rather than the standard flat rate, in a bid to encourage recycling.
That kind of program can create a backlash. Bill Walczak, a community activist and executive at Shawmut Design and Construction who is running for mayor, said he opposes "pay as you throw" because it can have a disproportionate impact on the poor and encourage illegal dumping.
But Connolly said, after the forum, that he would emphasize incentives for recycling over disincentives for large piles of garbage. And he said the program would not impose any new costs on homeowners. That could mean reducing property tax bills for those who face a hike in garbage removal costs.
Connolly, among the most fluid candidates on the issues, also pledged to bring recycling to all city parks, build bicycle lanes separated from car traffic and encourage "complete streets" planning, designed to accommodate pedestrians.
Walczak spoke of the importance of a mayor serving as a loud voice for environmental causes. State Rep. Martin Walsh, another candidate for mayor, said the city should explore taller buildings as a way to build density in the city — a goal favored by environmentalists concerned about sprawl.
George Bachrach, president of the Environmental League of Massachusetts and a co-sponsor of the forum, said he was pleased that the candidates embraced a green vision for the city.
"From our perspective, it's a pretty good crew," he said, of the candidates. "But they'll face competing pressures as mayor. So we want to hold their feet to the fire."
This program aired on July 9, 2013. The audio for this program is not available.