Fiscal 2023 Greenhouse Gas Emissions Inventory Finalized

The Zilkha Center recently completed the annual report on the college’s greenhouse gas (GHG) emissions. The inventory covers the most recent fiscal year (July 1, 2022 – June 30, 2023) and includes emissions from energy use on campus and by college-owned vehicles, electricity consumption, refrigerant and fertilizer use, waste management, food production and consumption, and even energy use by the Williams-Exeter Program at Oxford University.

Total assessed emissions amounted to 19,216 metric tons of carbon dioxide equivalent (MTCO2E). This was calculated using a market-based approach for emissions from purchased electricity which accounts for green attributes associated with electricity purchases, such as the college’s contract with NextEra for solar power at the Farmington, Maine solar PV facility. To put 19,216 MTCO2E into perspective, they are equivalent to the annual emissions of 4,178 average US passenger vehicles (using EPA figures).

For the second year, the emissions report includes estimates for food-related emissions. We added this important category last year to capture emissions arising during the entire food production chain up to consumption on campus as part of the college’s signing of the Cool Food Pledge.

Compared with the previous fiscal year, emissions increased by 7.6%, while remaining substantially below the FY91 baseline year (21.1% lower or 36.9% lower when excluding food-related emissions) and the peak emissions year FY03 (46.2% lower and 56.9% when excluding food-related emissions). Our total emissions trend since fiscal year 1991 is shown in Figure 1.

Figure 1: Annual total assessed GHG emissions for Williams College since fiscal year 1991. Note, since fiscal year 2022 we also include food-related emissions. For more information on the emission inventory’s boundaries, specific emissions sources included and other methodological aspects, please refer to the full report.

Although energy-related emissions declined slightly year-over-year, other categories saw increases, especially travel and food emissions. College-sponsored air travel emissions grew for the second year from 1,481 MTCO2E in FY22 to 2,429 in FY23 (64% increase) following a deep pandemic slump, while still coming in below the 4,799 MTCO2E in pre-pandemic FY19. Food emissions rose as well from 3,021 MTCO2E in FY22 to 3,845 MTCO2E in FY23 (up 27%), although the Dining Services team makes concerted efforts to create nutritious and tasty plant-rich offerings. These efforts seem to work as the increase in food emissions appears to largely be attributable to a growth in the total number of meals served, not an increase in per-plate emissions.

The largest source of emissions remains the central plant (10,465 MTCO2E equivalent to 55% of total emissions), although plant emissions have remained very stable since FY18 and well below peak emissions in the early 2000s when the plant predominantly used fuel oil. Since then, the plant has been converted to a cogeneration plant that generates electricity during the cold months and uses mostly cleaner-burning natural gas. It reaches more than 80% efficiency. Greater losses occur in the steam distribution system and some additional loss occurs at the building level. The long-term goal is to transition the campus away from steam to a more efficient, low-carbon energy source and distribution system that uses low-temperature hot water and heat pumps.

More data and detailed explanations can be found in the GHG emissions report. The Zilkha Center also gratefully acknowledges input and support from Competitive Energy Services, Planning, Design & Construction, Facilities Operations, Dining Services, the Office of the Provost, the Office of the Controller, and the Office of the VP for Finance and Operations.