NEW YORK – Power plants in the Northeast cut their carbon dioxide emissions by roughly 10 percent in the first three months of 2009 compared with the same period last year, according to a report released yesterday by the nonprofit advocacy group Environment Northeast.

The drop in carbon emissions from electricity-generation plants in Rhode Island and the nine other Northeast states in the Regional Greenhouse Gas Initiative (RGGI) cap-and-trade program was mainly due to a switch from burning coal to natural gas, which has plummeted in price over the past year, Reuters reported.

“Energy efficiency investments and the economic downturn are also contributing to reduced energy consumption, although lower energy consumption does not appear to be as large a contributor to declining emissions as increased use of low- or no-carbon fuels,” the report said.

Natural gas prices have been falling fast due to increased production, new reserve discoveries and reduced demand. Burning natural gas to generate electricity results in the emission of about half as much carbon as generating the same amount of power from coal.

Environment Northeast estimates that annual carbon emissions from the 10 states’ power plants were 19 percent below RGGI’s cap of 188 million tons, Reuters said.

Derek Morrow, Environment Northeast’s director of policy analysis, said the reductions in emissions in the Northeast was evidence that placing limits on greenhouse gases “can often be significantly cheaper to implement than originally forecast.”

The report comes as the U.S. House of Representatives prepares to vote today on a bill that would limit greenhouse-gas emissions and create a nationwide cap-and-trade program that would supersede RGGI. President Barack Obama has backed the legislation, known as the American Clean Energy and Security Act, Bloomberg News reported.