Skip to content

Additional categories

1. Context

The additional categories in this module are:

  • Commuting
  • Food
  • Waste

These categories are referred to as ‘additional’ because their emissions are calculated using EPFL campus data and rely solely on the number of unit FTE. They therefore do not provide specific information on the unit’s behaviour but are nonetheless useful for gaining a more comprehensive understanding of the order of magnitude of the unit’s carbon footprint.

2. Data collected

The data collected and used to calculate emissions for the additional categories relate to the number of staff and students at EPFL (via the Headcount module) plus other specific data described here:

  • Commuting: total number of kilometers per person (staff or students) and by mode of transport (cycle, car, public transport, etc.). These figures are calculated using responses from the Mobility survey sent out every two years to the EPFL community and combined with information on car park usage to estimate kilometers travelled by car.

  • Food: total quantity (in kg/person) of food purchased by type of person (staff or students), and by type (vegetarian and non-vegetarian). These figures are based on sales data from the various restaurants and food trucks on site, cross-referenced with the quantities of goods ordered.

  • Waste: total in kg/person of all non-hazardous waste, by type (paper, plastic, etc.) and by final treatment method (incineration, recycling, etc.). These figures are collected by the VPO each year.

3. Emission factors

  • Commuting: the emission factors used are those from the transportation environmental calculator, tool developped by Swissenergy. For cars, a factor specific to EPFL has been calculated based on the types of car used by the EPFL community. The factors are given in kg CO₂-eq/km by mode of transport (on foot, by bike, by car, by public transport, by motorbike).

  • Food: the emission factors used are based on goods orders placed at EPFL and are provided by the external service provider Beelong, which analyses the orders and quantities. The factors are in kg CO₂-eq/kg of food depending on the type (vegetarian or non-vegetarian).

  • Waste: emission factors are given in kg CO₂-eq/kg of waste (specific factors by type: paper, plastic, etc. and by treatment method: recycling, incineration, etc.). The factors are taken from Ecoinvent v3.12 (2026).

4. Methodology

Commuting

For each unit, the commuting carbon footprint \(CF_{commuting}\) is calculated as the product of the number of people in the unit, the average distance travelled by each mode of transport, and the emission factor associated with that transport mode, as follows:

\[ CF_{commuting} = \sum_{trans~type}^{} N_{students} \cdot Dist_{students, trans~type} \cdot EF_{trans~type} + \sum_{trans~type}^{} N_{staff} \cdot Dist_{staff, trans~type} \cdot EF_{trans~type} \]

Where:

  • \(trans~type\): public transport, cycling, car, walking, etc.
  • \(N_{students}\): total number of students per reference year in FTE
  • \(N_{staff}\): total number of staff members per reference year in FTE
  • \(Dist_{students,trans~type}\): distance travelled per student per mode of transport, in km
  • \(Dist_{staff,trans~type}\): distance travelled per staff member by mode of transport, in km
  • \(EF_{trans~type}\): emission factor for the mode of transport (kg CO₂-eq/km)

Food

The total CO₂ emissions related to food \(CF_{food}\) are estimated by aggregating, for each meal category (vegetarian or meat-based), the emissions associated with consumption by the student population and staff. For each unit, emissions are calculated as the product of the number of people in the unit, the average amount of food consumed per category, and the corresponding emission factor.

\[ CF_{food} = \sum_{food~type}^{} N_{students} \cdot Q_{students, food~type} \cdot EF_{food~type} + \sum_{food~type}^{} N_{staff} \cdot Q_{staff, food~type} \cdot EF_{food~type} \]

Where:

  • \(food_{type}\): type of food (vegetarian, non-vegetarian)
  • \(N_{students}\): total number of students per reference year (FTE)
  • \(N_{staff}\): total number of staff members per reference year in FTE
  • \(Q_{students,food~type}\): quantity of food purchased per student for the food type in kg/FTE
  • \(Q_{staff,food_type}\): quantity of food purchased per staff for the food type in kg/FTE
  • \(EF_{food_type}\): emission factor for the food type in kg CO₂-eq/kg

Waste

The total CO₂ emissions related to waste - \(CF_{waste}\) is obtained by multiplying the number of people in the unit by the amount of waste, based on its type and associated emission factor.

\[ CF_{waste} = \sum_{waste~type}^{}\sum_{eol}^{}(N \cdot Q_{waste~type, eol} \cdot EF_{waste~type,eol}) \]

Where:

  • \(waste~type\): type of waste (paper, plastic, etc.)
  • \(eol\): final treatment method (incineration, recycling, etc.)
  • \(N\): total number of staff per reference year in FTE
  • \(Q_{waste~type,eol}\): amount of waste per FTE in kg/FTE for the type and treatment
  • \(EF_{waste~type,eol})\): emission factor associated with the waste type and treatment method in kg CO₂-eq/kg

5. Limitations

The accuracy of these additional categories is limited by the lack of individual data specific to each unit:

  • For confidentiality reasons, it is not possible to know which members of a unit consume meat or vegetarian products, nor which modes of transport they use individually. Emissions are therefore estimated based on campus averages, without reflecting the unit’s actual behaviour. As a guide, meat generates significantly higher emissions than vegetarian alternatives, and the car is the mode of transport with the greatest impact.

  • As for waste, hazardous waste has been excluded from this analysis due to a lack of data enabling its consumption to be attributed to specific units. If the unit produces any, its actual emissions are higher than those estimated here.

6. References