Greenhouse Gas Emissions
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Greenhouse gas emissions (GHGs) from energy use, waste, and transportation trap heat and drive climate change impacts like rising temperatures, sea levels, and extreme weather. Cambridge is committed to significantly reducing GHGs by 2050 to help avoid these severe impacts.
About Greenhouse Gas Inventories
Our Goals
Cambridge is committed to reaching net zero greenhouse gas (GHG) emissions community-wide by 2050 or earlier. When we say 'net zero emissions' we mean that all the energy used in buildings in Cambridge, our transportation systems, and the management of our waste generates no emissions. To check progress toward this goal the City does a community-wide greenhouse gas inventory.
The City of Cambridge is part of the Global Covenant of Mayors (GCoM) a global network of cities that have committed to reducing emissions. As recommended we update our inventory every 3 to 5 years.
In 2026, the City updated the community-wide greenhouse gas emissions inventory to provide insights for years 2020 through 2024, and updates for years 2012 through 2019.
UNIT | Greenhouse gases (GHGs) have a natural heat trapping capacity which varies by gas. Humans produce more carbon dioxide (CO2) than any other GHG. We count emissions of GHGs based on how each GHG’s heat trapping capacity compares to CO2s. This is called the "CO2 equivalent" (CO2e). We measure GHGs in metric tons of CO2e (MTCO2e). | MTCO2eMetric Tons Carbon Dioxide Equivalent |
Greenhouse gases (GHGs) have a natural heat trapping capacity which varies by gas. Humans produce more carbon dioxide (CO2) than any other GHG. We count emissions of GHGs based on how each GHG’s heat trapping capacity compares to CO2s. This is called the "CO2 equivalent" (CO2e). We measure GHGs in metric tons of CO2e (MTCO2e). | MTCO2eMetric Tons Carbon Dioxide Equivalent |
About Greenhouse Gas Inventories
About Our Inventories
A greenhouse gas inventory is an estimated count of emissions produced from activities within a community. There are different kinds of greenhouse gas inventories that serve different purposes, are informed by different data sources, and have emissions calculated differently. A GHG inventory serves as a 'snapshot' of the volume of emissions from a moment in time. Doing GHG inventories on a regular basis helps identify trends that can inform policy. However, each time an inventory is done there are updates made to the data collected and how the emissions are calculated. Therefore, it can be difficult to directly compare one inventory to another, and focus should be on longer-term trends rather than year-to-year changes.
Inventories are organized in two distinct, but complimentary ways, by sector and scope. Scope reporting tells us where the emissions physically occur (inside or outside the city) and how they are associated with activity within the city. Sector reporting organizes emissions by sector which organizes emissions in ways that is more easily understood in our day-to-day.
The City of Cambridge regularly does two different greenhouse gas inventories, a community-wide inventory and a municipal operations inventory. The city is committed to updating its community-wide greenhouse gas inventory every 5 years. Our latest community-wide inventory covers years 2019 through 2024. The city does a municipal operations inventory every year. The municipal inventory helps inform the community-wide inventory, but the two should not be directly compared to each other.
Community-wide inventories are complex and there are many ways to understand the data. Below, we summarize some key findings from our 2024 Community-wide Inventory.
Community GHG Emissions
Scopes 1, 2 and 3 explained
Community-wide inventories are calculated using two approaches, the Scopes framework and the City-Induced framework. The Scopes framework categorizes emissions based on where they occur in relationship to the geographical boundary of the city and city activities. Whereas the city-induced framework organizes emissions based on what is causing the emissions, such as buildings or vehicles.
The Scope Framework consists of three levels being:
- Scope 1: direct greenhouse gas emissions from sources located with the city boundary, such as gasoline consumed by cars and natural gas used to heat buildings.
- Scope 2: indirect greenhouse gas emissions resulting from consumption of grid-supplied electricity, heat, steam, or cooling with the city boundary.
- Scope 3: indirect greenhouse gas emissions occurring outside of the City limits as a result of activities taking place within the City, such as treatment of the City’s waste outside of Cambridge city limits
Community GHG Emissions
What Sources are what Scope?
This chart shows the sectors, subsectors, and the emissions source of our community-wide inventory and identifies the emissions source's scope. For example, natural gas used in residential buildings fall into Scope 1 since the fuel is burned on-site within Cambridge. Whereas electricity used in residential buildings are considered as Scope 2 because the electricity is consumed within Cambridge, but the emissions made from creating that energy are produced outside of Cambridge. Then, the loss of electricity from where it is created to where is it consumed, otherwise known as during the transmission and distribution, is Scope 3.
| Sector | Subsector | Emissions Source | Scope 1 | Scope 2 | Scope 3 |
| Buildings | Residential Buildings | Natural Gas | X | ||
| Electricity Use | X | ||||
| Electricity Losses | X | ||||
| District Heating and Cooling | X | ||||
| Fugitive Emissions from Natural Gas | X | ||||
| Commercial and Institutional Buildings, and Manufacturing Industries | Natural Gas | X | |||
| Electricity Use | X | ||||
| Electricity Losses | X | ||||
| District Heating and Cooling | X | ||||
| Fugitive Emissions from Natural Gas | X | ||||
| Off-Road Equipment | X | X | |||
| Energy Industries | Stationary Combustion of Fuel | X | |||
| Construction | Off-Road Equipment | X | X | ||
| Transportation | On-Road | Fuels in On-Road Vehicles | X | ||
| Electricity Consumption on On-Road Vehicles | X | ||||
| Electricity Losses | X | ||||
| Rail | Fuels in Heavy and Light Rail | X | |||
| Electricity Consumption in Heavy and Light Rail | X | ||||
| Electricity Losses | X | ||||
| Waste | Solid Waste Disposal | Methane at Landfills | X | ||
| Biological Treatment of Waste | Direct Emissions from treatment | X | |||
| Incineration | Incineration | X | |||
| Wastewater Treatment and Discharge | Fugitive Emissions from Processing | X |
Municipal GHG Emissions
Trends Over Time
In 2015, the City of Cambridge set a goal to achieve net zero emissions by 2050. Later, the City established a specific goal for emissions from municipal operations, with a baseline year of 2008, to be cut by at least 30% by 2020 and a stretch goal of 35%. This target was met early in 2019, and now the City is now committing to reduce GHG emissions from municipal operations by 75% by 2030.
The City of Cambridge conducts a municipal greenhouse gas inventory every year to help inform progress toward this goal. Across the entire city, municipal operations account for about 1% of our total community-wide emissions.
This chart depicts the significant impact of the planned procurement of 100% renewable electricity supply from a new renewable system with a commercial operation date on or about Dec. 2025.