What Are Scope 3 Emissions?

Scope 3 emissions are indirect GHG emissions that occur in the value chain of the organization, both upstream and downstream. Accounting for Scope 3 emissions provides information about where in the value chain Cornell has the most opportunity to impact emission reductions.

Cornell includes scope 3 emissions from air travel, commuting and electricity transmission and losses in our baseline GHG inventory, aligned with Second Nature’s requirements and our carbon commitment. These Scope 3 categories are included because these transportation-based emissions are a direct result of Cornell’s policies and workforce and therefore Cornell has relatively more ability to manage them.

Additional Scope 3 emissions accounting

There are several challenges with accounting and performance tracking for Scope 3 emissions and with comparing them to the Scope 1 and Scope 2 emissions, including:

Lack of precise quantification methods, low data quality – it can be difficult to obtain sufficient information to do reliable estimates as there can be several emitters and the emissions can be from several geographic locations.
Unlike Scopes 1 and 2—which count directly controlled emissions —Scope 3 covers the entire value chain life cycle, creating inconsistent boundaries and ambiguous causation rules. The same emissions may be assigned to many actors across the value chain, and changes in emissions are difficult to evaluate or attribute.
The time scale of emissions – dependent on the category upstream and downstream emissions can occur over several years¹.

Cornell inventories many of these indirect emissions, but for most of them it makes more sense to do it separately from Scope 1 and 2 for comparability. Also, Cornell’s main reason for calculating GHG emissions is to obtain a base and inform decision-makers on the most impactful choices for reducing the university’s negative impact. This requires a different approach than calculating a comprehensive carbon footprint. The GHG Protocol’s Corporate Standard emphasizes Scope 1, 2, and selected 3 emissions within defined operational or equity boundaries. This structured approach avoids ambiguity and ensures accountability for emissions the entity can influence most directly. GHG Protocol reporting provides actionable insights for target-setting, risk management, and decarbonization strategies, whereas a “comprehensive carbon footprint” often includes indirect or speculative impacts that may dilute focus and hinder comparability.

Scope 3 emissions from fuel and energy related activities (upstream methane) are accounted for annually and published in our additional inventory.

This accounting area includes methane emissions from extraction and delivery of the gas burned at the campus Central Energy Plant. The IPCC Special Report on 1.5C (SR 1.5) states that the primary driver of climate change is cumulative anthropogenic carbon dioxide (CO2) emissions. This results from both the huge scale of the emissions due to human activity and because 20-35% of anthropogenic CO2 emissions stay in the atmosphere for thousands of years, and thus accumulates. Climate forcers like methane are much more potent on a per-molecule basis (120 fold), and therefore contribute significantly to near-term temperature forcing, but do not accumulate in the atmosphere like CO2. Nonetheless, the IPCC AR5 report concludes that 25% of the current contribution to human-caused global warming is due to methane emissions. Further, many peer-reviewed papers published since 2012 show that reaching the UN COP21 target of keeping the planet well below 2oC is most easily accomplished by reducing both carbon dioxide and methane emissions. The IPCC AR6 report reinforces the need for parallel and complementary strategies to slow warming in the near term, avoid overshoot, and limit warming in the long term.

Meaningfully accounting for methane is complicated. The Global Warming Potential (GWP) metric was created to compare the impacts of different gases. GWP relates the warming potential of a given molecule (e.g., methane) to that of CO2. Because methane oxidizes to CO2 in the atmosphere, its residence time is less than that of CO2 and its GWP varies with time. The IPCC defines three standard values, GWP20 (based on a 20-year average following a pulse emission of methane), GWP100 (based on a 100-year average) and GWP500 (based on a 500-year average). All of these are relevant for analyzing the impact of upstream methane leakage on climate. The peak temperatures from climate change that we are trying to avoid are likely to occur close to 2100, but on the other hand methane emissions contribute significantly to the rate of global warming over the next 20 to 40 years. Hence the relative importance of the two molecules on climate is constantly changing.

Learn more about Global Warming Potential as a metric from the US EPA and the UNFCC IPCC:

Cornell currently uses natural gas as a fuel source to heat and power the Ithaca campus as part of our district energy system's combined heat & power production at the Central Energy Plant (CEP). The modern CEP has several advantages over the retired coal-fired heating plant and separate procurement of electricity from the New York State grid. First, natural gas produces much less carbon dioxide than coal, per unit of energy produced. Second, the plant uses the waste heat from its electric turbines to heat the campus, increasing overall efficiency when the heat is also needed. These efficiencies have led to a substantial reduction in the carbon dioxide footprint of the campus. However, upstream leakage of methane from extraction and distribution of natural gas counteracts some of that benefit on the 20-30 year time scale. Cornell is therefore committed to eliminating its use on campus, and tracks both GWP20 and GWP100 for the upstream methane emissions associated with the natural gas consumed on campus.

For additional context, a mass balance analysis shows that for a constant source like the Cornell CEP, methane does not accumulate in the atmosphere like CO2 does, but rather approaches a steady state value over a 20-30 year time frame. Further, while precise data is not readily available to calculate the emissions of upstream methane associated with Cornell's use of coal for heat and grid electricity prior to converting to combined heat and power in 2010, we estimate that Cornell's upstream methane emissions haven't changed significantly given the efficiency gains from combined heat and power and the fuel mix of power generators on the NY grid at the time.

Emissions from downstream waste are also accounted for separately and on an annual basis.

A preliminary assessment of the full supply chain of purchases (upstream purchased goods) across Cornell has been done twice, in 2019 and 2021. The methodology of the assessment was developed by Professor Natalie Mahowald, Earth and Atmospheric Sciences, the Campus Sustainability Office, and a student research team in partnership with Cornell Atkinson Center for Sustainability and The Sustainability Consortium.

While Cornell does not account annually for all Scope 3 emissions, the additional inventory section will be updated when new information is available. Our main priority is to create the best base for decision making and progress evaluation in Cornell’s effort of reducing the carbon footprint and mitigating climate change. Because of this, the focus will be on emissions categories that Cornell has an opportunity to impact.

How are we reducing Scope 3 Emissions?

There are several ongoing and planned initiatives to change the Cornell community's behavior to lower the footprint and reduce the Campus’ overall Scope 3 emissions:

Incentives for Carpooling
Free bus for staff, faculty, and first year students
Efforts to make walking and bike riding at campus safe and preferable
Access to Electrical Vehicle charging on Campus

Reductions in air travel emissions continue to be a challenge however a cross-campus working group has identified and attempts to advance land-based carbon sinks and sequestration practices to counterbalance carbon emissions
A Campus-to-Campus bus drives daily between Ithaca Campus and Weill Medical College on Manhattan, New York City. The bus can be used by anyone wanting to travel between the two cities

Food scraps from Cornell Dining’s kitchens are sent to composting. Some dining areas also allow customers to drop off food waste for composting. Organic waste is composted at Cornell’s Industrial Compost Facility
Most dining halls on campus offer reusable takeout containers, reducing single use plastic demand
Recycling bins can be found at all public areas throughout campus, inside and outside. Cornell supplies all campus offices with single-stream recycling bins for paper, cardboard, plastic, tin, and glass. Each week 26 tons of recycled materials on average are collected and diverted from landfills. R5 is responsible for Cornell’s Ithaca Campus Solid Waste and Recycling program
Dump & Run is an annual initiative where students leaving campus can donate their items for reselling to students moving in each August. Tons of items are diverted from the waste stream

Our efforts to reduce the use and dependency of fossil fuels for power and heating will at the same pace reduce emissions of upstream methane

The CSO office is partnering with Cornell's Procurement team to advance procurement sustainability by working directly with WB Mason to initiate a soft swap process. When launched, dozens of products frequently purchased by Cornell employees will have sustainable alternatives suggested within a popup window before check-out. In addition to being more sustainable, these products are vetted to be cost-neutral or cost-saving.

¹Excellent information about the “Scope 3 problem” can be found on the GHG Management Institute blog series – What is Greenhouse Gas Accounting