The methodology below has been prepared by Yasmine Baghdadi with support from the IZP: Our Campuses team; Procurement department; and Energy, Engineering, and Environment department.

Methodology basis

Scope 3 emissions encompass all indirect greenhouse gas emissions associated with activities outside the direct control and ownership of Imperial College London. Scope 3 emissions of goods and services were calculated based on the approach used in the Higher Education Supply Chain Emissions Tool (HESCET). Modifications have been implemented to the tool to make it more specific to Imperial as an academic institution and aid in categorising scope 3 emissions.

In general, the HESCET approach entails classifying procurement spent by Procurement Higher Education (ProcHE) coding. This coding is then mapped to 311 standard categories set by the Department of Environment Food and Rural Affairs (DEFRA) with known spend-based emission factors. Once mapped, an aggregated spend for each DEFRA category is calculated and multiplied by the respective emission factor to derive the carbon dioxide equivalent emission (CO₂e).

The 311 DEFRA categories could be grouped into 12 high-level sectors representing different areas of spend. A detailed breakdown of the sectors and their representation are summarised in Table 1.

Table 1: List of high-level grouping of DEFRA categories and a description of each.

CATEGORY	INCLUSIONS
Food and non-alcoholic beverages	All food products ranging from fruits and vegetables to meats, spices, condiments, and confectionary. All non-alcoholic drinks such as tea, coffee, juices, soft drinks, and water.
Alcoholic beverages and tobacco	Alcoholic beverages and any tobacco products like cigars or cigarettes.
Clothing and footwear	Any purchased garments or footwear, personal protective clothing, clothing raw materials, and laundry services.
Housing	Broken down into expenditure on rentals, maintenance raw materials and services, regular charges, and utilities.
Furnishings and household	Includes all purchases of furniture, textiles, appliances, tools, and disposables.
Healthcare	Includes all healthcare products and services.
Transport	Includes all vehicle purchases, maintenance, and services. Accounts for all travel spend.
Information and communication	Includes postal and mobile services, electronics purchases and internet subscriptions.
Recreation and culture	Includes any purchases of equipment or supplies used for audiovisual, recreation, or leisure activities such as student societies or clubs.
Education	All education-related spend such as trips and tutorial equipment.
Restaurants and accommodation	Includes all expenditure on external catering and business travel accommodation and expenses.
Personal care and accessories	Includes all personal purchases as well as insurance, financial, and legal services.
Others	Any miscellaneous purchases

Moreover, in our endeavour to refine the reporting process, it is worth noting that the HESCET utilises DEFRA emissions categories originally designed for households, rendering them somewhat incongruent when applied to the intricate landscape of large organizations like Imperial. Recognizing this discrepancy, we have undertaken a meticulous review and restructuring of some emission categories within the tool. This strategic adaptation ensures that the categories now align more seamlessly with our specific areas of purchasing, enabling a more accurate and contextually relevant assessment of our procurement-related emissions. This tailored approach is instrumental in enhancing the tool's effectiveness for our organizational context, providing a nuanced understanding of our environmental impact associated with purchased goods and services.

Changes implemented to the HESCET Tool

To ensure an accurate reporting of scope 3 emissions, the HESCET tool mapping and categorisation was revised:

• Emission factors for all categories were revisited and updated (where needed).
• The mapping of ProcHE codes to the 311 DEFRA categories was revised.
• New categories were created (21 in total) based on the mapping revision and divided into two high-level emission sectors:
  • Laboratory and research: includes all purchase of lab materials, equipment, and supplies as well as scientific research and development services and chemical waste disposal.
  • Professional and bought-in services: Includes all technical, computer, insurance, financial, and educational services purchased externally.

The 21 new categories were adding on to the original HESCET tool and mapped accordingly with the relevant ProcHE codes. Mapping for these categories was internally revised to ensure the validity of the proposed changes. Emission factors for the new categories were gathered from different databases and are explained in detail in Section 5.

• Where possible, a mass-based calculation approach was used and integrated into the HESCET tool. For example, to calculate transmission and distribution (T&D) emissions for electricity, the kWh spend of electricity was multiplied by the mass-based emission factor for T&D. A similar approach was used for water and gas emissions. The final utility emissions were added into the respective category in the results table.
• A recategorization of the emission sectors was implemented in such a way that the different categories matched with Imperials College’s procurement department category managers.

Emissions recategorization

Imperial college spend items were re-grouped according to the existing college organisation structure for ease of data analysis, future monitoring of emissions and decision making (Table 2). The categorisation process was quality checked by the personnel involved in the procurement and management of the respective items.

Table 2: List of categories used for emission grouping and a description of each.

CATEGORY	INCLUSIONS
Capex	Major equipment and projects
Furniture	Furniture for offices, laboratories, and communal spaces
IT services	Software, hardware, IT Support and Data Centres, audio visual (equipment and refurbishment of facilities) and MFDs (photocopiers, printers spares and peripherals)
Medical supplies	Medical equipment and services
Laboratory and research	Laboratory chemicals, gases, consumables, and equipment
Business services	Professional and bought-in services, recruitment (temporary and permanent), recruitment advertising.
Construction	Estates, projects, minor works, and maintenance
Food and catering	Purchases of food and catering services
Travel	Business-related travel and expenses associated with it
Paper products	Stationary, printing, and other library services
Estates	Includes utilities, health, safety, security, and facilities operations
Other products	Miscellaneous purchases

 

To perform the calculations for the different categories in this methodology, reverse engineering of the HESCET mapping was implemented as follows:

• New emission factors were calculated for each ProcHE code derived from the existing DEFRA emission factors. The new factor was assumed to be a weighted average of the factors used for the categories considered for each ProcHE code based on the mapping.
• The new factor was multiplied by its relevant ProcHE code to calculated emissions.
• Each ProcHe code was categorised based on the groups presented in Table 2.

The new system was referred to as “Emissions per actionable group”.

Emission factors

Two main methodologies were implemented to calculate scope 3 emissions of goods and services based on the type of available data.

• A mass-based methodology was implemented for emissions from transmission and distribution of electricity and gas due to the availability of energy data per hour. Updated emission factors were found in the most recent greenhouse gas reporting publication released by the Department of Energy Security and Net Zero as well as the Department of Business, Energy, and Industrial Strategy (BEIS). [1]
• A spend-based methodology was used to assess emissions from all remaining purchased goods and services since the data was provided by the procurement department in amount spent. Spend-based emission factors were gathered from a variety of sources. Priority was given to factors provided by BEIS. Where not found, emission factors from the United States Environmental Protection Agency (EPA)[2] or the European environmental Agency (EXIOBASE) [3].

Procurement and Supply Chain Emissions Analysis

In this results section, we delve into the findings of our scope 3 emissions analysis using the actionable groups categorisation outlined in the methodology section. This approach involved collaborating closely with Imperial’s procurement team and their category managers. We have organized our results into practical groups that offer a clearer view of the environmental impact linked to our purchases. This tailored method not only ensures the accuracy of our findings but also paves the way for targeted sustainability efforts in areas where they can make the most difference.

The detailed breakdown of carbon emissions within specific subcategories provides a nuanced perspective on Imperial College London's environmental impact (Table 3)

Table 3: Ranked breakdown of procurement & supply chain categories and their respective CO₂ emissions

Rank	Category	Subcategory	Emissions (tonnes CO2e)	Percentage of total procurement emissions
1	IT services	Audio Visual and Multimedia Supplies and Services	872.76	0.73%
		Library services	9072.15	7.59%
		Computer Supplies and Services	33933.67	28.40%
		Printing, Reprographics and Photocopying	24.22	0.02%
		Telecommunications	176.88	0.15%
		Stationery and Office Supplies	0.00	0.00%
2	Travel		24845.60	21.04%
3	Laboratory/Research	Materials	775.42	0.65%
		Equipment	22007.25	19.58%
		Services	0.00	0.00%
4	Business services	Library services	677.72	0.57%
		Technical services	8483.90	7.10%
		Insurance and legal services	450.67	0.38%
		Financial services	122.64	0.10%
		Education services	768.66	0.64%
		Miscellaneous services	860.30	0.72%
5	Estates	Utilities	1469.37	1.23%
		Health, safety, and security	500.96	0.42%
		Estates, and facilities operations	7242.08	6.08%
		Fees	1713.39	1.43%
6	Food and catering	Food	673.27	0.56%
		Beverages	42.05	0.04%
		Equipment and services	1663.89	1.39%
7	Construction		469.00	0.40%
8	Furniture		448.21	0.38%
9	Other products		411.11	0.35%
10	Paper products		284.94	0.24%
11	Medical supplies		43.81	0.04%
12	Capex		36.15	0.03%
13	Unclassified		0.00	0.00%

Within IT services, significant contributors include computer supplies and services and library services, contributing 33,933.67 tonnes and 9,072.15 tonnes, respectively, making up a substantial share of the overall emissions. Notably, the emissions from computer supplies and services highlight the substantial environmental implications of digital infrastructure management.

In the Laboratory/Research category, emissions primarily stem from equipment and materials, accounting for 22,007.25 tonnes and 775.42 tonnes, respectively. this underscores the importance of sustainable practices in research-related activities. Food and catering emissions are notable in the equipment and services subcategory, contributing 1,663.89 tonnes, 70 % of the sector, emphasizing the need for sustainability considerations in food sourcing and catering operations which have been outlined in the Imperial College London Sustainable Food and Drink Policy.

Estates-related emissions span various subcategories, such as utilities, health, safety, and security, estates, facilities operations, and fees, revealing the diverse sources within the institution's physical infrastructure. Among the different subcategories, facilities operation emits around 66 % of the sectors CO₂e. Finally, business services showcase emissions from various service-oriented subcategories, including library services, technical services, insurance and legal services, financial services, and education services underscoring the varied impact of administrative and support functions on the carbon footprint.

The reported low construction emissions are due to an accounting practice where spending for construction projects is recorded when the contract is awarded and payment is made, not when the work is done. This approach results in a lumpy representation of construction-related emissions, reflecting financial transaction timing rather than real-time emissions from construction activities. Understanding this methodology is crucial for accurate interpretation, highlighting the importance of considering financial timelines in emissions reporting.

Sources

Student and staff statistics: College overview | About | Imperial College London

2023: Greenhouse gas reporting: conversion factors 2023 - GOV.UK (www.gov.uk)

2022: Greenhouse gas reporting: conversion factors 2022 - GOV.UK (www.gov.uk)