Maryland would become one of a handful of states to commit on its own to reducing global-warming pollution under legislation approved in both chambers of the General Assembly.
The House of Delegates voted, 107-31, Friday for the measure, which would require the state to cut greenhouse gases by 25 percent by 2020; the Senate approved its version earlier this month. Lawmakers said they expect to easily resolve differences between the two versions and send the bill to Gov. Martin O'Malley for his signature.
"Doing nothing is no longer an option," said Del. Kumar P. Barve, the majority leader and Montgomery County Democrat. "We can no longer treat the atmosphere as if it were a big free garbage dump."
O'Malley has made efforts to improve the environment a cornerstone of his administration and co-sponsored a bill that had failed in recent years. This year's legislation represents a compromise hammered out with input from industry, labor and environmentalists - one that exempts the entire manufacturing sector.
The Democratic governor said in a statement that the environmental benefits of the bill come at a critical time as the state works to protect more than 3,000 miles of coastline sensitive to rising ocean levels.
Republicans questioned how much Maryland could contribute to stemming a global problem, and some doubted global warming is real. Some also warned the bill would impose a "hidden tax" on residents through higher electricity costs. Republicans tried to include manufacturers in the plan, but the amendment failed.
"Our constituents can't exempt themselves from the bill," said House Minority Leader Anthony J. O'Donnell, a Southern Maryland Republican.
Other mandates adopted in recent years to promote conservation and energy efficiency will help the state reach its climate-change goals, said Del. Brian K. McHale, a Baltimore Democrat: "Everyone will eventually be using less electricity. The cheapest kilowatt is the one that's not used."
The bill doesn't set out how to achieve the goals; the state Department of the Environment would have to set a plan for doing so by 2012. Any plan would have to yield a net economic benefit to the state and not disrupt affordable and reliable electricity service, among other requirements.
The vast majority of greenhouse gas emissions in Maryland, mostly carbon dioxide, come from electricity consumption and transportation sources. Manufacturing accounts for about 5 percent of emissions.
Under the plan headed toward final passage, state regulators must submit a progress report to the General Assembly by 2015. Lawmakers would then be able to continue the effort, or it would expire the next year.
Seven other states have passed similar legislation requiring greenhouse gas reductions, according to the National Conference of State Legislatures.