Boston's Carbon Emissions
Explore Boston's community and municipal greenhouse gas inventories.
Overview
In 2022, the Boston community emitted 5.70 million metric tons of greenhouse gasses (GHGs) from energy use in buildings and transportation. This is nearly a 2.5% increase from 2021, when Boston emitted 5.59 million metric tons. This increase may largely be attributed to higher use of natural gas (also known as methane gas) in large buildings. Citywide emissions are reported by calendar year. The City of Boston has established an ambitious climate action agenda, aiming to achieve net-zero greenhouse gas emissions by the year 2050. As part of this long-term vision, the city has set an interim target of reducing citywide emissions 50% by 2030, relative to baseline levels.
Boston 2022 Community GHG Emissions
Economic and Population Growth
The increase from 2021 Boston’s emissions occurred alongside population and economic growth in the city. The Boston community has grown from 521 thousand residents in 2005 to 699 thousand residents in 2022. Emissions per resident over the same time period have decreased 42%, from 14 to 8 metric tons per year. Boston's economic growth, as measured by Gross City Product (GCP), has increased from 103 billion dollars to 175 billion. Emissions per million dollars of GCP have decreased 51%, from 70 to 34 metric tons per million dollars.
Community-wide emissions
Community emissionsMayor Michelle Wu has committed to achieving a Green New Deal for Boston, by tackling the climate crisis with strategies that address economic, social, and racial inequities. Eliminating greenhouse gas emissions that drive climate change is core to the vision, along with building resilience to a changing climate, and underpin Boston’s Climate Action Plan. To measure progress, Boston follows the Global Protocol for Community-Scale Greenhouse Gas Emission Inventories (GPC). The baseline year is 2005, the first year in which consistent and reliable data was collected. Boston has a goal to achieve a 50% reduction by 2030 and net-zero greenhouse gas emissions by 2050.
The annual greenhouse gas (GHG) inventory is based on a combination of direct data and estimates for data that cannot be obtained directly. Data sources include City records, utility company reports, and information from state and federal agencies. Reporting is separated into community-wide and local government operations inventories. Because the data for these inventories is collected using separate protocols on separate timescales, the Local Government Operations Inventory should be considered to be overlapping, but not completely contained within the Community Inventory.
What's included?
- Energy used by buildings and other stationary sources; fugitive emissions from methane distribution within Boston limits.
- On-road and some off-road transportation, and public transportation trips within city limits.
- Wastewater treatment within city limits.
What's not?
- Emissions generated outside the city boundary to produce goods or services used by residents (for example, emissions from food produced elsewhere but consumed by Bostonians, or airplane emissions that cannot be attributed specifically to Boston).
Boston will continue to evaluate the benefits and challenges of “consumption-based” emissions accounting as a complement to the current inventory methodology.
The goal of the community inventory is to include GHG emissions associated with all activities — residential, commercial/industrial, institutional, transportation-related — within the administrative boundary of the City of Boston. The Boston community-wide inventory accounts for emissions from the following sources:
- Stationary energy use from residents, businesses and other activities, including municipal buildings.
- On-road and off-road transportation, including municipal vehicle fleet fuel use (airplane travel at Logan airport excluded).
- Solid waste and wastewater disposal and treatment.
In Boston, energy use in stationary sources dominates, accounting for 70% of total emissions (4.0 MtCO2e). Commercial, industrial, and large residential buildings generated 51% of emissions (2.9 MtCO2e), while small residential buildings accounted for 18% of emissions (1.1 MtCO2e). Fugitive gas emissions for all sectors account for less than 1% (12 thousand tCO2e) of emissions. Emissions in the building sector stem from the use of electricity (42%), natural gas (47%), fuel oil (8%), and steam (3%).
Individual buildings over 20,000 square feet publicly report their energy and water usage annually. The data is available at: Analyze Boston.
- Commercial, industrial and large residential buildings, including high-rise offices, hospitals, universities and research buildings, manufacturing, and construction
- Small residential buildings
- Fugitive emissions from oil and natural gas (or methane gas) systems
Emissions from transportation comprise 29% of the inventory (1.6 MtCO2e). This is lower than transportation’s share of statewide or national emissions because of Boston’s density and robust public transportation system. More than half of Bostonians get to work via a mode other than a car. (Go Boston 2030).
The inventory captures the emissions from the estimated Vehicle Miles Traveled (VMT) inside the City, plus public transportation vehicles and off-road vehicles used at the airport and wastewater treatment plant. Primary sources of energy in transportation include gasoline (78%), diesel (19%), natural gas (<1%), electricity (2%), and biodiesel and propane combined (<1%).
GHGs reported in the waste sector refer to emissions from wastewater treatment only and account for less than 1% of total emissions (19 thousand tCO2e). All, or almost all, of Boston’s solid waste is sent to Waste To Energy (WTE) incineration plants that feed the electricity grid, so emissions are counted as part of regional electricity generation. Boston has a Zero Waste initiative and the indirect accounting of emissions from solid waste in our GHG inventory does not affect the City’s commitment to waste reduction.
short-term changes
In 2022, the community’s GHG emissions increased 2% (136 thousand tCO2e) from the previous year. These increases reflect that:
- Boston businesses and institutions have increased their energy use; the commercial and industrial building sector consumed 10% more electricity and 8% more natural gas compared to 2021.
- Boston experienced an increase of 5% in small residential buildings’ electricity consumption compared to 2021. Additionally, the city’s population grew by approximately 44,000 residents, according to recent census data.
- Boston vehicle miles traveled (VMT) decreased by 5% from 2021 to 2022. After a sharp post-pandemic increase of 12% from 2020 to 2021, VMT remains lower than pre-pandemic levels.
- Despite an overall increase in energy use, Boston’s greenhouse gas emissions per person have decreased by 3.5%, indicating progress in energy efficiency, cleaner energy sources, and emissions reduction efforts across the city.
LONG-TERM CHANGES
Boston’s GHG emissions from 2005 to 2022 have declined by 22.1%. Approximately half of GHG emissions reduction since 2005 has been due to state-level and regional action to clean the New England electric grid. While VMT have increased since 2005, the impact of increased traffic has been counteracted by improved fuel economy, as the average vehicle registered in Massachusetts has improved from 18.6 miles per gallon (mpg) in 2005 to an estimated 23.9 mpg in 2022.
The energy efficiency efforts of the City’s programs, Boston’s utilities, local government and many businesses, institutions, and residents have also offset much of Boston’s recent growth. The City has also adopted additional policies and programs to decrease our emissions, such as the Building Emissions Reduction and Disclosure Ordinance or the ZEV Roadmap.
The inventory employs measured data, projections, models, and, where data is scarce, best estimates. All of these sources have some level of uncertainty, most of which have not been quantified. Furthermore, the inventory is frequently revised as new and better data become available, models are improved, new methodology is developed, and international standards evolve. For these reasons, longer term trends are likely more reliable than absolute numbers or year-to-year changes.
Municipal emissions
Municipal emissionsThe Local Government Operations (LGO) inventory calculates all greenhouse gas emissions generated by municipal operations in the City of Boston. This includes the burning of fuels in the City’s facilities, vehicles, and other equipment, and the energy used in municipal buildings, vehicles, parks, street lights, and traffic signals. The LGO inventory is based on the ICLEI greenhouse gas reporting protocol for local government operations.
Under the protocol, emissions that are not under the operational control of the City government or involve leased properties are excluded. Emissions from the Boston Housing Authority, the Massachusetts Water Resources Authority (MWRA), and the Boston Planning and Development Agency (BPDA) are not included in the inventory. Those from the Boston Public Health Commission (BPHC) and the Boston Water and Sewer Commission (BWSC) are.
While the timeframe for the citywide inventory is the calendar year, the LGO inventory is conducted on the fiscal year, from July to June. Because the data for these inventories is collected using separate protocols and on different timescales, the LGO should be considered to be largely overlapping but not completely contained within the Citywide inventory.
In FY22, municipal emissions increased by 6%, but are down more than 35% from 2005 before including adjustments for the purchase of renewable energy credits. Previously, the City of Boston had purchased Green-e certified RECS, but ceased the practice in 2019. In Fiscal Year 2023, the City evaluated options for a direct investment in renewable energy. The City of Boston is working toward its municipal goal of reducing greenhouse gas emissions by 60% by 2030.
Boston’s LGO emissions are dominated by building energy consumption. Electricity and gas consumption by buildings each make up about one third of total GHG emissions. Transportation fuels, diesel and gasoline, together make up one fourth of total municipal GHG emissions.
Similar to the community-wide inventory, Boston’s municipal operations GHG inventory trends are driven by a number of external and internal factors. Diesel consumption is continuing to decrease as Boston Public Schools switches its fleets from diesel- to propane-powered school buses. The continued downward trend in the regional electric grid emissions rate also contributed to reduced emissions.
As the department with the largest building portfolio, and the second largest vehicle inventory (after Boston Police Department), Boston Public Schools (BPS) represents the largest source of municipal emissions. BPS owns and operates approximately 12 million of the City’s 16 million square feet of building space across the roughly 127 school buildings in the district. These buildings represent approximately one third of municipal electricity consumption and two thirds of municipal gas consumption.
The BPS Department of Transportation (BPS-DOT) fleet of over 700 vehicles uses nearly half of all the diesel fuel consumed by City government. BPS has continued their replacement of the oldest, dirtiest diesel buses to lower emissions propane engines, which in FY22 comprised over one quarter of the fleet. Since BPS-DOT is on a roughly 10 year replacement cycle, these lower emissions vehicles will provide emissions reductions over the next decade.
The next largest source of GHG emissions from municipal operations is the Public Works Department’s street lights. The 66,000 electric street lights and the 2,800 natural gas street lights found in Boston’s historic districts account for 9% of total municipal GHG emissions. Street lighting used to make up a much larger share of Boston’s municipal GHG profile; however, aggressive conversions of electric street lights to LEDs dating back to 2010 have cut emissions from street lights in half. While gas lamps comprise just 4% of total street light fixtures, they produce 37% of GHG emissions from street lights.
Short-Term
- The increase in FY22 emissions can be attributed to modest increase in energy usage across multiple sources, including vehicle fuels for City fleet (gasoline, diesel, and propane) and energy use in municipal buildings (electricity and natural gas).
Long-Term
- The electricity emissions factor decreased as described in the community inventory.
- Natural gas and heating oil use has decreased over the long term (especially in recent fiscal years) as the City converted some older schools from oil to gas, and opened new, energy-efficient buildings that use natural gas for heat and hot water.
- Electricity use has decreased over the long term, primarily driven by the near complete conversion of Boston’s 66,000 electric streetlights to more efficient LED fixtures. Boston has also invested in building energy efficiency measures on a project-by-project basis, and plans to engage in deeper energy efficiency retrofits as part of the Renew Boston Trust program.9
Inventory methodologies
MethodologyThe City of Boston is party to the Global Covenant of Mayors (GCoM), which requires the City to follow the Global Protocol for Community-Scale Greenhouse Gas Emission Inventories (GPC). Boston utilizes the GPC framework and publishes a full methodology to share our inventory approach.
- Learn more about the GHG Protocol for Cities
- Boston Greenhouse Gas Inventory Methodology (last revised in June 2024)
Boston’s GHG inventories are reported in CO2 equivalents (or CO2e), a universal unit of measurement that accounts for the global warming potential (GWP) of different greenhouse gasses. Boston’s inventory includes carbon dioxide (CO2), natural gas (CH4), and nitrous oxide (N2O), and uses Global Warming Potentials (GWPs) from the latest version of the International Panel on Climate Change (IPCC) Guidelines (currently 5AR). The formula used to determine the CO2e from a given energy use is Activity Data x Emissions Factor1+2+3 = GHG Emissions from Activity,
Boston currently is choosing to report at the GCP BASIC level, which covers scope 1 and scope 2 emissions from stationary and transportation sources, as well as scope 1 and scope 3 emissions from waste.
- Scope 1: GHG emissions from sources located within the City boundary.
- Scope 2: GHG emissions occurring as a consequence of the use of grid-supplied electricity, heat, steam, and cooling within the City boundary.
- Scope 3: All other emissions that occur outside the City boundary as a result of activities taking place within the city boundary.
2022 data revisions
- Incorporated newly published ISO-NE emissions factors that account for imported electricity from New York and Canada, providing a more accurate reflection of the carbon intensity of electricity consumed in Boston. These updated factors have been applied retroactively to 2005, resulting in a revised emissions baseline.
- The City adopted a new methodology to calculate residential fuel oil use, based on the U.S. Energy Information Administration’s Short-Term Energy Outlook for seasonal average consumption, adjusted to reflect Boston’s winter weather conditions.
We will continue to develop methodological updates to improve consistency across City policies and reporting frameworks.
The Local Government Operations inventory methodology for calculating GHG emissions is based on the ICLEI greenhouse gas reporting protocol for local government operations, developed by ICLEI and the National Association of Clean Air Agencies. The protocol categorizes emissions as direct (Scope 1) or indirect (Scope 2). Direct emissions come from the burning of natural gas (or methane gas), fuel oil, gasoline, diesel fuel, and other fuels in the City’s facilities, vehicles, and other equipment. Indirect emissions come from the burning of fuels in facilities owned and operated by others to produce electricity, and steam that the City uses. Emissions that are not under the operational control of the City government, or involve leased properties, are excluded. Emissions from the Boston Housing Authority, the Massachusetts Water Resources Authority (MWRA), and the Boston Planning and Development Agency (BPDA) are not included in the inventory. Those from the Boston Public Health Commission (BPHC), and the Boston Water and Sewer Commission (BWSC) are.
In 2013, the City invested in an Enterprise Energy Management System (EEMS) and an Energy Manager to track and report local government energy consumption, cost, and GHG emissions. Prior years’ reporting relied on annual data collection from numerous stakeholders in the auditing, budget, and purchasing offices. This manual process sometimes led to inconsistent data collection from year to year. Now the process is almost entirely automated, and with complete invoice data for over seven calendar years entered, the City can track progress towards energy and GHG reduction goals on a monthly basis. By tracking this data more closely, the City is able to identify which departments, buildings or assets are contributing most to our overall portfolio, and in the process, has identified errors in utility bills worth over $1.2 million in credits back to the City.