Regional air emissions 2016: long-term reduction trends continue
Wednesday, January 31, 2018 at 1:12PM
ISO New England in Industry News & Developments, energy efficiency, environment, natural gas, new england states, oil, renewable resources, solar

Since 2001, SO2 down 98%, NOx down 73%, CO2 down 29%

Driven primarily by a decrease in coal and oil generation, regional emissions of sulfur dioxide (SO2), nitrogen oxides (NOx), and carbon dioxide (CO2) declined between 2015 and 2016, according to data compiled for the 2016 ISO New England Electric Generator Air Emissions Report. The year-over-year declines continued long-term reductions in the emissions generated by the region’s power plants.

Year-over-year changes: 2016 vs. 2015

The below tables summarize the year-over-year changes for total system emissions (the amount of system emissions) and emission rates (the pounds of emissions given off, on average, with every megawatt-hour [MWh] of electricity produced). This is akin to comparing how many gallons of gasoline a car used versus its miles per gallon (MPG). Between 2015 and 2016, the region saw declines in both emission amounts and rates for SO2, NOx, and CO2.

2015 and 2016 New England system emissions (ktons) and emission rates (lb/MWh)

Several key factors contributed to the decreases between 2015 and 2016:

The chart below shows each fuel type’s contribution in 2016 by month.

2016 ISO New England monthly generation by fuel type (% MWh, MWh)

Long-term trends: 2001–2016

Total emissions for SO2 and NOx declined from 2001 to 2016 by 98% and 73%, respectively, while CO2 emissions decreased by 29%. The below table and graphs from the emissions report show the total amount of air emissions on an annual basis in kilotons (kTons), as well as the emissions rates over the last decade.

Annual Emissions of NOX, SO2, and CO2, 2001 to 2016 (kilotons)

New England system annual emissions of NOX, SO2, and CO2, 2007 to 2016 (ktons)

New England system annual average NOX, SO2, and CO2 emission rates, 2007 to 2016 (lb/MWh)

A shifting fuel mix

The type and magnitude of a generator’s emissions are directly linked to the type of fuel that powers it, and the fuel mix used to produce New England’s electricity has changed significantly over the past decade.

Percentage energy generation by fuel type, 2007 compared with 2016

Natural gas-fired resources account for the vast majority of new generators built in New England since 1997. This ongoing trend to meet electricity needs with higher-efficiency, lower-emitting gas-fired generators instead of oil- and coal-fired generators has been the biggest contributor to the long-term decline in regional emissions. Transmission system upgrades have further reduced the need to run older, less efficient oil and coal units.

The region’s increasing development of wind, solar, and other zero-emission resources will further contribute to reducing greenhouse gases. As of August 2017, about 55% of all proposed projects in the generation interconnection queue are wind-power resources.

More imported electricity

Since 2004, lower-priced electricity from outside New England has increasingly flowed in to serve regional demand. This external generation, which served 17% of New England’s energy needs in 2016, doesn’t count toward regional air emissions.

Less demand for electricity from the regional power system

Since about 2005, annual regional demand for wholesale electricity has been declining, and with it, so has electricity generation. The economic downturn and slow recovery helped dampen electricity consumption. Several long-term factors have also been at work to reduce the amount of power consumers pull from the grid:


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