As the City of Boston begins the implementation of Community Choice Energy and prepares to release the Carbon Free Boston report, BCAN members are debating what we might do next to help reduce greenhouse gas (GHG) emissions in Boston. To make the most impactful choices, we need to know which sources contribute the most to GHG emissions and how that distribution has been changing over time.
The following data and graphs are based on the City of Boston’s Community Greenhouse Gas Emissions dataset and the related report, “City of Boston Greenhouse Gas Emissions Inventory 2005–2016.” The City tracks emissions in the following categories: large, commercial buildings (which includes residential buildings with 10 or more units); residential buildings; transportation; waste; and fugitive gas (from all sectors). As shown in Figure 1, the largest contributor to GHG emissions is the commercial buildings sector, followed by transportation, then residential buildings. Waste water and fugitive gases (gas leaking from pipelines in the city) contribute a negligible amount, according to the metrics used by City staff.
Between 2005 and 2016, the most progress in GHG reduction was made in the commercial buildings sector, followed by small residential buildings. The transportation sector barely managed to reduce emissions.
In Figure 2, the contribution of each of the three largest sectors is further dissected into its various components (electricity, natural gas, fuel oil, and steam for buildings; vehicle fuel (for vehicles other than the municipal fleet), municipal fleet, and MBTA for transportation).
Between 2005 and 2016, most of the GHG reduction from commercial buildings came from electricity, while emissions from natural gas increased slightly. Fuel oil and steam showed large proportional declines, but their contribution to overall emissions is relatively small. In small residential buildings, electricity and fuel oil made the highest contributions to the reduction. Over 90% of the emissions in the transportation sector come from vehicle fuel.
Some of the factors driving GHG emissions down are as follows:
- Switching power plants from coal (and oil) to gas
- Increasing the proportion of clean energy (solar, wind, hydro) in the electricity mix
- Conversion of oil heat to gas heat
- Better insulation of buildings
- Saving electricity due to efficient appliances and lighting
- Better fuel efficiency of cars in general and increased proportion of hybrids and electric vehicles
It should be pointed out that GHG emissions reductions from replacing coal and oil with natural gas will reach a plateau. According the U.S. Energy Information Administration, natural gas emits 25% less CO2 than heating oil and 50% less CO2 than coal for the same amount of energy produced (although these calculations don’t take into account the leaking of methane during fracking and from pipelines, as pointed out by the Union of Concerned Scientists, among others). However, natural gas is still a fossil fuel that emits GHG.
There are also some factors that tend to drive GHG emissions up:
- Increase in population, requiring more residential buildings
- Increase in economic output/GDP, requiring more commercial buildings
- Increase in traffic (vehicle miles traveled)
These data and considerations would suggest that some of the most urgent and effective measures to bring down GHG emissions would be greening the electrical grid at a much faster pace (which is the goal of BCAN’s CCE campaign), replacing natural gas as a heating source with electrical heat pumps, better insulating old and new buildings, replacing gasoline as vehicle fuel (more electric vehicles), and reducing the miles traveled in cars by getting more people to use public transportation, bike, and walk.
Note: The data used to generate the graphs (plus more graphs and analysis) can all be found at this link: https://docs.google.com/spreadsheets/d/1SWi9P4fyUvFZXOXSwqyFX5VvH-bS3afg_R-DOpmr2Gg/edit?usp=drivesdk