AU's Greenhouse gas emissions report
The greenhouse gas emissions report provides an overview of Aarhus University’s direct and indirect CO2 emissions in 2025, calculated according to the Greenhouse Gas Protocol (GHG). The report first provides a brief introduction to the methods used. The main results for 2025 are then presented.
Summary
Summary
According to Aarhus University’s Climate Strategy 2020–2025, the goal for 2025 is to reduce the university’s CO2 emissions by 35 per cent against a 2018 baseline. Progress towards the emissions reduction targets is monitored in the annual greenhouse gas emissions reports for the so-called baseline emission categories, for which reliable data and consistent methodologies make it possible to track trends from the beginning of the reporting period. Table 1 provides an overview of the areas for which emissions are inventoried in the 2025 report, as well as the areas that are (also) included in the baseline categories.
Table 1: Areas covered by Aarhus University’s greenhouse gas emissions report 2025
| Scope | Area | Baseline category (35 per cent goal) |
| 1 | On-site heating (gas) Transport Agriculture | ✔ ✔ ✔ |
| 2 | District heating Electricity | ✔ ✔ |
| 3.1 3.1 3.2 3.3 3.5 3.6 3.15 | Purchases of goods and services Water and wastewater (subset) Purchases of capital goods Fuel and energy-related activities Waste Air travel Investments |
|
In 2025, Aarhus University emitted 30,398 tonnes of CO2 within the baseline categories covered by the 35 per cent goal. This corresponds to an 8 per cent reduction compared to 2024 and a 43 per cent reduction compared to the 2018 baseline.
The reduction since 2018 is mainly due to a reduction in water consumption, less air travel, the phasing-out of oil and a reduction in gas consumption for heating, as well as external factors such as a greener energy mix for electricity. The development should be viewed in light of an approximately 15 per cent increase in full-time equivalents during the same period, which means that CO2 emissions per employee have been reduced from 6.8 tonnes of CO2 in 2018 to 3.4 tonnes of CO2 in 2025 – equating to a reduction of approximately 50 per cent.
It is important to note here that the ‘water and wastewater’ category constituted a significantly larger share of baseline category emissions in 2025 than in previous years. This is because, in the latest version of its emissions factor database, the Danish Climate Compass has revised the emissions factor for wastewater management substantially upwards. As a result, the historical time series has also been recalculated using the updated factors.
Purchases of goods, services and capital goods (scope 3.1 and scope 3.2) are not included in the baseline categories, but are worth highlighting as they constitute the largest individual emission categories in the greenhouse gas emissions inventory. Aarhus University’s emissions were an estimated 61,440 tonnes of CO2 in 2025.
Additional scope 3 factors such as fuel and energy-related activities (scope 3.3), waste (scope 3.5) and investments (scope 3.15) are also not included in the baseline categories, but in these areas the university emitted a total of 1,027 tonnes of CO2 in 2025.
Finally, the greenhouse gas emissions report contains a comprehensive overview of changes compared to previous reports, including both isolated corrections of previous years’ activity levels and the retrospective updating of emission factors.
Methods
Methods
Below is a review of the methodological framework and the methods used by Aarhus University to report emissions in this greenhouse gas emissions report. The methods are exactly the same as those used in the university's most recent greenhouse gas emissions reports.
Methodological framework
Aarhus University’s greenhouse gas emissions report was prepared using the GHG protocol.
The GHG protocol divides the emissions attributable to an organisation into three different scopes, i.e. three difference sources of CO2 emissions:
- Scope 1 Emissions from sources that AU controls directly (for example, combustion of petrol andoil)
- Scope 2: Emissions that AU causes indirectly by purchasing energy (electricity and district heating)
- Scope 3: Emissions AU is indirectly responsible for in connection with the products and services AU consumes and employee air travel.
Methods
To calculate Aarhus University’s CO2 emissions, two main methods were used: the activity-based method and the financial data-based method. Here is why multiple methods have been used.
Aarhus University’s first greenhouse gas emissions report was for 2018. This report is the baseline for calculating subsequent developments in the university’s CO2 emissions and in relation to the university’s climate targets. When the 2018 report was prepared, it was possible to collect relatively reliable CO2 data for emissions within scope 1, scope 2 and for air travel and water (scope 3). This data was calculated using the activity-based method (see more below).
The university’s CO2 emission reduction targets were set based on the categories of emissions it was possible to measure at the time. These constitute the ‘baseline emission categories’ and include:
- Scope 1 On-site heating (oil and gas), transportation and agriculture (crops and livestock)
- Scope 2: District heating and electricity
- Scope 3: Air travel and water (water and wastewater)
Since 2020, more sources of emissions have been added to the greenhouse gas emissions report, which enables a larger proportion of the university’s total emissions to be calculated and included in the report. Specifically, the following sources of CO2 emissions have been added.
- Fuel and energy-related activities (scope 3.3), waste (scope 3.5) and investments (scope 3.15), all of which are calculated using the activity-base method. However, these emissions cannot be directly compared with a baseline, because no data are available from 2018.
- Goods and services (scope 3.1) and capital goods (scope 3.2), which are calculated using a financial data-based method.
Here is a more detailed breakdown of both methods, including their applications and limitations. All of the methods used also comply with a methodological framework developed by the green house gas reporting group under Universities Denmark.
The activity-based method
The activity-based method is used in the greenhouse gas emissions report to calculate CO2 emissions. The calculations are based on concrete data for emissions from different sources, for example consumption of energy and fuel and travel activity. Unlike the financial data-based method (described below), which bases calculations on expenditure in Danish kroner, the activity-based method bases calculations on physical units of measurement – such as kWh, litre or kilometre – which are multiplied by specific emission factors.
The emission factors are typically sourced from national or international databases, such as the Danish Energy Agency’s standard factors or DEFRA (UK). These factors take the type of activity and energy source into account. For example, district heating consumption is multiplied by an emission factor that reflects the heating plant’s energy mix and efficiency.
In addition, the method uses some emission factors developed by Aarhus University’s own researchers. These factors are also used in the national carbon emission inventories.
This method makes more precise and direct calculations of emissions possible when detailed data on consumption is available. It is particularly suitable for calculating scope 1 and 2 emissions (such as direct emissions from petrol consumption and energy purchases). It can also be used for selected categories in scope 3 for which activity data are available.
One limitation of the activity-based method is that it relies on detailed, accurate data reporting for each activity, which is not always possible.
The financial data-based method
Since Aarhus University first began preparing greenhouse gas emissions reports, there have been improvements in how CO3 emissions are calculated. This has made it possible to include emissions from a wider range of activities in the university’s emission inventory. An important contributor to this development has been the introduction of the financial data-based method, which was used in for the first time in AU’s greenhouse gas emissions report for 2020.
The financial data-based method is used to calculate scopes 3.1 and 3.2, which cover emissions from the purchase of goods, services and capital goods.
To link data on consumption with emission factors, the method uses classifications that correspond to the categories of goods and services used in AU’s financial accounting – such as standardised product codes in the UNSPCS (United Nations Standard Products and Services Code). This makes it possible to assign relevant emission factors to specific categories of goods and services for which it would otherwise be impossible to calculate CO2 emissions at this point in time.
The method provides a broad, holistic picture of the organisation’s climate footprint. However, it also has certain limitations:
- The emission factors are based on sector averages within relatively broad financial categories, which means they do not reflect deviations at product or organisational level.
- The reference data is typically several years older than the current accounting period.
- The method is not suitable for comparing emissions over time, as it assumes that one krone spent within a given category represents a fixed amount of CO2. This means that when the university purchases more expensive goods in a particular category, it may appear that emissions have increased, even though actual emissions associated with production are not necessarily higher. Conversely, switching to cheaper goods within a category can give the impression of a reduction in emissions, even though actual emissions are virtually unchanged.
However, the method is becoming continually more refined and accurate as more product categories are added, and because emission factors are gradually being developed for more specific subcategories.
When preparing the greenhouse gas emissions report for 2023, Aarhus University used a new tool from a private IT supplier. Using artificial intelligence and machine learning, this tool does a better job of matching the university’s expenditure with the appropriate emission factors. As a result, more of AU’s financial activities can be included in the greenhouse gas emissions report. In addition, the supplier is also starting to include product-specific emission factors from selected suppliers in the tool, which will make it possible to prepare a more detailed greenhouse gas emissions report in future.
With this approach to continued methodological development, it is to be expected that it will be necessary to revise reports from previous years based on new knowledge. This is a natural consequence of working with an area in which advances are constantly being made.
Result
Result
An inventory of Aarhus University’s CO2 emissions in 2025 is presented below.
The results for the baseline emission categories are presented first.
Then follows a presentation of the results for scope 3.1 and scope 3.2, covering emissions from purchases of goods and services (3.1) and capital goods (3.2). These are calculated using the financial data-based method.
Finally follow the results for fuel and energy-related activities (scope 3.3), waste (scope 3.5) and investments (scope 3.15). These areas, like the baseline categories, are calculated using the activity-based method, but lack a basis of comparison going back to 2018.
Results for baseline categories
In Table 2 an overview of the estimated CO2 emissions in 2025 for the baseline categories is presented. Aarhus University emitted a total of 30,398 tonnes of CO2 in the baseline categories. This corresponds to an 8 per cent reduction compared to 2024 and a 43 per cent reduction compared to 2018.[1]
Table 3 provides an overview of CO2 emissions per employee within the baseline emission categories. Compared to 2024, emissions have been reduced by 11 per cent per employee, and by 50 per cent per employee compared to 2018. This reduction should be viewed in light of an approximately 15 per cent increase in the number of full-time equivalents during the same period – from 7,871 full-time equivalents in 2018 to 9,033 in 2025.
Developments within the various categories are explained in more detail below.
Table 2: Aarhus University’s CO2 emissions in 2025 for baseline categories
| Scopes | Category | Tonnes CO2 |
|---|---|---|
| Scope 1 | On-site heating (oil and gas) | 674 |
| Transportation | 1,222 | |
| Agriculture | 3,676 | |
| Scope 2 | District heating | 1,412 |
| Electricity | 3,038 | |
| Scope 3 | Water & wastewater | 13,532 |
| Air Travel | 6,845 | |
| Total | 30,398 |
Table 3: Aarhus University's CO2 emissions per employee in 2018 to 2025 (FTE)
| Description | 2018 | 2019 | 2020 | 2021 | 2022 | 2023 | 2024 | 2025 |
|---|---|---|---|---|---|---|---|---|
CO2 emissions in tonnes per employee | 6.8 | 5.3 | 3.7 | 3.5 | 4.5 | 4.4 | 3.8 | 3.4 |
Development compared to 2018 | -21% | -45% | -48% | -34% | -35% | -44% | -50% |
Scope 1
For scope 1 emissions, the following development was seen for the categories ‘on-site heating’, ‘transport’ and ‘agriculture’.
On-site heating
In 2025, Aarhus University emitted 674 tonnes of CO2 in the ‘on-site heating’ category, which includes the consumption of gas (especially on Viborg Campus). This equates to a 14 per cent increase compared to 2024, but still represents a 60 per cent decrease compared to 2018.
The increase occurred despite a 2 per cent decrease in the total consumption of natural gas and biogas in 2025. The increase in CO2 emissions was due to a n increase in purchased natural gas relative to biogas in 2025. This was due to instability in the supply of biogas during the winter months, when the need for heating is greatest. To compensate for this, it was necessary for Aarhus University to purchase and use a larger share of natural gas.
Transport
In 2025, Aarhus University emitted 1,222 tonnes of CO2 in the ‘transport’ category, which covers consumption by Aarhus University’s cars, work vehicles and research vessel (Aurora) as well as work-related driving using employees’ own cars. This corresponds to a 7 per cent increase compared to 2024, and a 4 per cent increase compared to 2018. The development since 2024 has been driven, in particular, by increased levels of activity for the university’s research vessel Aurora – from 65,984 litres of diesel in 2024 to 90,491 litres in 2025.
It is also worth noting that the development in emissions from 2018 to 2025 cannot be assumed to be completely consistent over time, as Aarhus University only started including petrol and diesel consumption from employees driving their own cars in connection with the 2022 greenhouse gas emissions report. If the comparison is limited to transport categories that can reasonably be assumed to be consistent over time – namely Aarhus University's own vehicles and Aurora – emissions decreased by 23 per cent over the period.
Agriculture
In 2025, Aarhus University’s agricultural activities emitted 3,676 tonnes of CO2. This corresponds to a 6 per cent increase compared to 2024, which still represents a 22 per cent reduction compared to 2018. The development over the reporting period was driven, among other things, by a reduction in emissions from dairy cattle as well as improved manure management for both dairy cattle and swine.
Scope 2
For scope 2 emissions, the following development was seen for the ‘district heating’ and ‘electricity’ categories.
District heating
In 2025, Aarhus University emitted 1,412 tonnes of CO2 in the ‘district heating’ category. This corresponds to a 40 per cent reduction compared to 2024, and a 36 per cent reduction compared to 2018. The reduction in the past year is due, in particular, to a significantly lower emission factor for district heating from Kredsløb in Aarhus, which supplies most of the university’s district heating. Even though activity levels in this category also decreased in 2025, most of the reduction in CO2 emissions can be attributed to a change in the fuel mix in the district heating system. However, over the entire period from 2018 to 2025, Aarhus University’s actual consumption of district heating fell by 26 per cent.[1]
Electricity
In 2025, Aarhus University emitted 3,038 tonnes of CO2 in the ‘electricity’ category. This corresponds to a 31 per cent reduction compared to 2024, and a 70 per cent reduction compared to 2018. The development can be explained, in particular, by the transition to a greener energy mix in Denmark and in the municipalities where the university’s buildings are situated, following an expansion of solar and wind energy capacity. At the same time, the university has reduced its electricity consumption by 12 per cent since 2018.
Scope 3
For scope 3 emissions, the following development was seen for the ‘water and wastewater’ and ‘air travel categories.
Water and wastewater
In 2025, Aarhus University emitted 13,532 tonnes of CO2 in the ‘water and wastewater’ category. This corresponds to a 15 per cent increase compared to 2024, but still a 35 per cent reduction compared to 2018. The development can be attributed, in particular, to a significant reduction in water consumption in the first part of the reporting period.
In the latest version of the emissions factor database, the Climate Compass has revised the emissions factor for wastewater management (see also the ‘Corrections and changes’ section) substantially upward. As a result, the water category this year accounts for a significantly larger share of emissions for the baseline categories than in previous years.
Air travel
Aarhus University emitted 6,845 tonnes of CO2 in the ‘air travel’ category. This corresponds to a 26 per cent reduction compared to 2024, and a 46 per cent reduction compared to 2018. The development is largely due to a reduction in the average length of flights in 2025 (measured in km), while there was actually a slight increase in the number of registered flights.
Results for other scope 3 categories
Goods and services (scope 3.1) and capital goods (scope 3.2)
As noted, the calculation of CO2 emissions resulting from purchases of goods, services and capital goods is a relatively new addition to the greenhouse gas emissions inventory, and has been performed using financial data-based method.
Taken together, these categories represent the largest sources of emissions in Aarhus University's greenhouse gas inventory (see the 'Total emissions' section below).
Table 4 shows that in 2025, Aarhus University emitted 54,860 tonnes of CO2 from purchases of goods and services (scope 3.1) and 6,580 tonnes of CO2 from purchases of capital goods (scope 3.2).
Table 4. Aarhus University’s CO2 emissions in 2025 from goods, services and capital goods
| Scopes | Tonnes CO2 |
|---|---|
| Goods and services (scope 3.1) | 54,860 |
| Capital goods (scope 3.2) | 6,580 |
| Total | 61,440 |
The five largest categories of scope 3.1 CO2 emissions (UNSPSC codes) are as follows:
- Laboratory and measuring and observing and testing equipment (6,931 tonnes of CO2)
- Management and business professionals and administrative services (3,924 tonnes of CO2)[1]
- Furniture and furnishings (3,777 tonnes of CO2).
- Building and facility construction and maintenance services (3,352 tonnes of CO2)
- Live plant and animal material and accessories and supplies (3,327 tonnes of CO2)
Fuel and energy-related activities (scope 3.3), waste (scope 3.5) and investments (scope 3.15)
Table 5 provides an overview of CO2 emissions from fuel and energy-related activities (scope 3.3), waste (scope 3.5) and investments (scope 3.15). As stated in the ‘Methods’ section, no data for these categories is available going back to the 2018 baseline year, and for that reason they are not included in the baseline categories.
Table 5. Aarhus University’s CO2 emissions in 2025 from fuel and energy-related activities, waste and investments
| Scope | Tonnes CO2 |
|---|---|
| Fuel and energy-related activities (scope 3.3) | 313 |
| Waste (scope 3.5) | 9 |
| Investments (scope 3.15) | 705 |
Fuel and energy-related activities (scope 3.3)
Table 5 shows that Aarhus University emitted 313 tonnes of CO2 from fuel and energy-related activities in 2025. This category includes emissions associated with the production and transportation of fuel used by Aarhus University which is not included in scope 1. It includes, for example, emissions from the extraction, refining and transportation of fuel. Emissions in 2025 correspond to a 4 per cent increase compared to 2024 and correlate with the general increase in the transport category (scope 1).
Waste (scope 3.5 )
Table 5 shows that Aarhus University emitted 9 tonnes of CO2 from waste in 2025, which corresponds to a 7 per cent reduction compared to 2024. The development is primarily due to lower emission factors for many waste categories.
Investments (scope 3.15)
Table 5 shows that Aarhus University emitted 705 tonnes of CO2 from investments. This corresponds to a 1 per cent reduction compared to 2024. In other words, emissions from the investment category are approximately on par with the previous reporting year.
Corrections and changes to previous greenhouse gas emissions reports and new initiatives
Corrections and changes to previous greenhouse gas emissions reports and new initiatives
Corrections and changes to previous greenhouse gas emissions reports and new initiatives
(a) Updated water and wastewater consumption figures
In connection with the calculation of water consumption in 2025, more precise consumption figures have been calculated for the period 2018 to 2024. This is due, among other things, to double/overlapping registrations in previous years. For the same reason, historical water consumption figures have been updated, and CO2 emissions calculated retrospectively.
The updated water consumption from 2018 to 2025 is shown in Table 6.
Table 6. Overview of Aarhus University’s water consumption 2018–2025
| 2018 | 2019 | 2020 | 2021 | 2022 | 2023 | 2024 | 2025 | |
|---|---|---|---|---|---|---|---|---|
| Consumption (m3) | 370,862 | 274,037 | 259,634 | 227,314 | 259,597 | 242,169 | 208,988 | 239,497 |
(b) Updated emission factors for water and wastewater (2018–2024)
The Climate Compass emission factors, on which Aarhus University’s estimated CO2 emissions for water and wastewater are based, have been updated (again) this year. Worth noting is the fact that the emission factor for wastewater management has increased by a factor of approximately 6 due to an update of the underlying Exiobase database. One reason is that newer calculations take more account of so-called process emissions, which are released directly from the basins when wastewater is treated. New research has shown that these process emissions contribute much more to the total emissions from wastewater than previously assumed.
The emission factors have been corrected retrospectively to 2018, which ensures a more accurate calculation of CO2 emissions for these years. But this essentially means that the CO2 emissions for the ‘water’ category constitute a much larger share of the university’s total emissions in the baseline categories.
The updated emissions from 2018 to 2025 are shown in Table 7.
Table 7. Overview of CO2 emissions from water and wastewater 2018–2025
| 2018 | 2019 | 2020 | 2021 | 2022 | 2023 | 2024 | 2025 | |
|---|---|---|---|---|---|---|---|---|
| Water (tonnes of CO2) | 863 | 638 | 604 | 529 | 604 | 564 | 486 | 557 |
| Wastewater (tonnes of CO2) | 20,091 | 14,845 | 14,065 | 12,314 | 14,063 | 13,119 | 11,321 | 12,974 |
It is important to stress that the update to the emission factor for wastewater does not alter the overall picture as regards the university’s progress towards achieving its climate target; Aarhus University has achieved the 35 per cent goal, regardless of whether the reporting is based on the old or the new emission factor for wastewater.
(c) Updated emissions from agriculture
In connection with the calculation of emissions for agriculture in 2025, more precise emissions for 2018 to 2024 have also been recalculated. In general, a slight downward adjustment of CO2 emissions has been made for specific emission sources, but since the deviation is approximately the same for all the years calculated, the impact on the overall achievement of the 35 per cent goal is minimal.
The updated emissions from 2018 to 2025 are shown in Table 8.
Table 8. Overview of CO2 emissions from agriculture 2018–2025
| 2018 | 2019 | 2020 | 2021 | 2022 | 2023 | 2024 | 2025 | |
|---|---|---|---|---|---|---|---|---|
| Agriculture (tonnes CO2) | 4,686 | 4,661 | 4,026 | 4,265 | 3,899 | 3,857 | 3,467 | 3,676 |
(d) Typo under fuel and energy-related activities (scope 3.3) in the greenhouse gas emissions report for 2024
In the greenhouse gas emissions report for 2024, the effect of marine diesel was calculated and counted twice in the calculation of CO2 emissions under scope 3.3. The actual emissions in 2024 amounted to 292 tonnes rather than 338 tonnes of CO2 as stated in the report for 2024. Scope 3.3 is – as highlighted – not included in the baseline categories, and thus this correction does not alter the overall picture with regards to the university’s achievement of its climate target.