Methodology

We believe that good solutions come with the use of scientifically sound approaches and transparency. This is why we are sharing the information about how we calculate $CO_2$ emissions from the user inputs. For this, we need so-called emission factors, which allow us to convert units of activity (e.g., distance travelled in km) to greenhouse gas emissions in $CO_2$ equivalents.

You can find the source code and data in our GitHub repository.

Anthropogenic climate change is caused by greenhouse gases, such as carbon dioxide ($CO_2$), methane ($CH_4$), nitrous oxides ($N_2O$) and others. The molecules of these gases contribute differently to global warming. For example, the impact of one methane molecule is 21 times higher than the impact caused by one carbon dioxide molecule (Moss et al. 2000). This is why the impact of different greenhouse gases is usually converted to the equivalent impact that carbon dioxide molecules would have. Therefore, for carbon footprint calculations, $CO_2$ equivalents are used as a standard unit (Gohar & Shine 2007).

The co2calculator can compute emissions caused by four big areas of the work life: electricity, heating, business trips and commuting. These were identified as the major emission sources by Jahnke et al. (2020), who calculated the carbon footprint of their research institute. Emissions are given as $CO_2$ equivalents $E$ [kg].

Business trips and field trips are assessed on an individual level whereas heating and electricity are assessed once for the entire research group.

The emissions $E$ are calculated using emission factors $\epsilon$ from different sources:

• Probas: electricity, heating, most cars, buses, trains
• UBA (2021). "Umweltfreundlich mobil": bicycles, pedelecs, trams
• GOV.UK (2020). Greenhouse gas reporting: conversion factors 2020: planes, ferries, electric cars, motorbikes

More information about the sources of the emission factors can be found in chapter 6 of this document.

The specific emission factors for different activities are collected in this emission factor table.

The basic formula is $E = \epsilon \times C$, with $E$ being the $CO_2$ equivalents, $\epsilon$ being a specific emission factor and $C$ being consumption (e.g. of electricity).

For electricity the user can select between the German electricity mix or solar power. The German electricity mix applies, if the research institute has a regular German electricity contract. Solar power is applicable, if the institute uses self-generated power from solar panels. The user is asked for the annual electricity consumption $C$ [kWh] which is then used to calculate the $CO_2$ equivalents $E$ [kg]. Since the emission factors $\epsilon$ for heating and electricity in the ProBas database apply for a consumption of 1 TJ, the consumption needs to be converted from kWh to TJ with a conversion factor of 277777.7778.

$\underline{\text{Example:}}$ $3942.6 \text{ kg} = 109518 \text{ kg/TJ} \times \frac{10000 \text{ kWh}}{277777.7778}$

If the electricity consumption is only known for a building or building complex and the group occupies only parts of the building and uses only parts of the appliances, the total consumption and an estimate of the share of energy use (approximated from the share of the building area) can be provided.

The user is asked about the annual consumption $C$ and the energy sources for heating, based on which the $CO_2$ emissions $E$ are determined. Heating consumption can be provided in kWh, or in other units, depending on the fuel type (see this conversion table):

• Oil: l
• Liquid gas, Coal, Pellets, Wsoodchips: kg
• Gas: $m^3$

The conversion factors $\kappa$ are retrieved from:

• BAFA (2020): Merkblatt zur Ermittlung des Gesamtenergieverbrauchs
• Krajnc, N. (2015): Wood fuels handbook, FAO

The emission factors \epsilon_{\text{heating}} depend on the fuel type. Fuel types may be oil, gas, liquid gas, electricity, coal, district heating, different types of heat pumps (ground, air, water), pellets, woodchips and solar.

$\text{\underline{Example:}}$ $2360.8 \text{ kg CO2e} = 65578 \text{ kg/TJ} \times \frac{10000 \text{ kWh}}{277777.7778}$

If the heating consumption is only known for a building or building complex and the group occupies only parts of the building, the total consumption and an estimate of the share of energy use (approximated from the share of the building area) can be provided.

The co2calculator allows to quantify the $CO_2e$ emissions $E$ [kg] for individual business trips for different modes of transport. The $CO_2$ equivalent is a function of the distance $D$ travelled in km. This distance may either be directly provided, or it may be computed from given start and stop locations using distances.py. In the latter case, the coordinates of the locations have to be retrieved by geocoding and then the travel distance between the locations is computed. Next to the distance or the locations, the user defines the mode of transport and its specifica.

Geocoding is done using the openrouteservice geocoding service, which is built on top of Pelias, a modular, open-source search engine for the world.

To find airports (geocoding_airport), we use Pelias search with the search text "IATA-code + Airport". For this, the user is asked to provide the IATA-codes of the start and end airport. To find train stations inside the EU (geocoding_train_stations), we use the train station database of Trainline EU. For this, the user is asked to provide the country and the name of the start and the end train station. For train trips outside of the EU and other modes of transport, we use structured geocoding (geocoding_structured). The structured geocoding parameters are:

• country: highest-level administrative division supported in a search. Full country name or two-/three-letter abbreviations supported
  • e.g., Germany / "DE" / "DEU"
• locality: equivalent to what are commonly referred to as cities (also municipalities)
  • e.g., Bangkok, Caracas
• address: street name, optionally also house number

For cars and motorbikes, distances are computed with openrouteservice with the profile='driving-car'.

For other modes of transport (airplane, ferry, train, bus), the distances between the locations as the crow flies are computed with the haversine formula. Then, different detour coefficients or constants are applied. With the roundtrip option, users can define if their trip is a roundtrip in which case the distance will be doubled.

Detour

Trips on earth will always make a detour, because it is usually not possible to travel in a straight line from start to destination. Therefore, we use coefficients and constants to account for this detour. These differ depending on the mode of travel.

Business trips include five transportation types: car, train, bus, airplane, and ferry. Generally, the $CO_2e$ emissions $E$ in kg per passenger are calculated by multiplying the distance $D$ with a specific emission factor $\epsilon$. For all transportation modes except for car, the given emission factors are already in passenger kilometers. For cars, the emission factors we are using are in vehicle kilometers, so we multiply the distance by the emission factor and divide it by the number of passengers.

$E_{\text{car}} = \epsilon_{\text{car}} \times \frac{D}{n}$

$E_{\text{bus/train/plane/ferry}} = \epsilon_{\text{bus/train/plane/ferry}} \times D$

$\text{\underline{Example (long-distance train):}}$ $16 \text{ kg CO2e} = 0.032 \text{ kg/P.km} \times 500 \text{ km}$

The emission factors $\epsilon$ are specified according to the transportation modes and their specifica, which are shown in the table below. We ask the user to give the values for the following specifica. If no value is given, the values marked in bold are used as default values.

Trips are categorized based on their ranges, which can be used later for analysis and visualization purposes.

• Very short haul: < 500 km
• Short distance: 500 - 1500 km
• Medium distance: 1500 - 4000 km
• Long distance: > 4000 km

$CO_2e$ emissions $E$ [kg] from commuting are also quantified individually for each mode of transport calc_co2_commuting. For a given mode of transport, the user provides the average weekly distance $D_{\text{weekly}}$ travelled in a given time period (work_weeks). Available transportation modes are:

• Car
• (Local) bus
• (Local) train
• Tram
• Motorbike
• Bicycle
• Pedelec

Emissions from commuting are calculated the same way as emissions from business trips by multiplying the weekly distance $D_{\text{weekly}}$ by an emission factor $\epsilon$:

$\text{\underline{Example (bus):}}$ $1.95 \text{kg CO2e} = 0.0389 \text{kg/P.km} \times 50 \text{km}$

The emission factors $\epsilon$ are specified according to the transportation modes and their specifica, which are shown in the table below. We ask the user to give the values for the following specifica. If no value is given, the values marked in bold are used as default values.

If we assume that a representative sample of $n$ persons of the entire group, consisting of $N$ members, entered their commuting data, we can obtain an estimate of the commuting emissions for the entire group:

with $E_{\text{aggr}}$ being the sum of the $CO_2e$ emissions of all participants.

The web portal ProBas provides process-oriented basic data from different projects. Most emission factors we use for commuting and business trips originate from TREMOD, the Transport emission model (IFEU Heidelberg & UBA, 2019). ProBas uses data from the 2010 project, i.e., Version 5 (IFEU Heidelberg & UBA, 2010). Emission factors for specific car fuel types, and for heating and electricity come from GEMIS (Globales Emissions-Modell Integrierter Systeme), a freely available computer model with an integrated database for lifecycle assessments and CO2 footprints of energy, resource and transport systems (ÖKo-Institut & IINAS, 2021). It was developed by the Öko-Institut and then passed to the International Institute for Sustainability Analysis and Strategy (Internationales Institut für Nachhaltigkeitsanalysen und -strategien - IINAS) in 2012.

The brochure "Umweltfreundlich mobil!" by the Umweltbundesamt (Federal Environmental Agency) of Germany assesses the environmental impact of different modes of transport (UBA, 2021). The emission factors for bicycles, pedelecs, and tram were taken from Table 3 on p. 38 of this brochure.

This comprehensive set of conversion factors provided by the UK Department for Business, Energy & Industrial Strategy is intended for use by companies and other organizations to report on their greenhouse gas emissions. We have used conversion factors for planes, ferries, electric cars, and motorbikes from this source.

In the plots of your emissions dashboard, your remaining carbon budget is visible as a green line. This is meant as a coarse figure that you can compare your emissions to. “The term ‘carbon budget’ refers to the maximum amount of cumulative net global anthropogenic CO2 emissions that would result in limiting global warming to a given level with a given probability, taking into account the effect of other anthropogenic climate forcers. This is referred to as the total carbon budget when expressed starting from the pre-industrial period, and as the remaining carbon budget when expressed from a recent specified date (Glossary). The remaining carbon budget indicates how much CO2 could still be emitted while keeping warming below a specific temperature level" (IPCC 2021, p. 28).

To calculate the remaining carbon budget, we followed an equal-per-capita approach. This means that the remaining global carbon budget is distributed equally among the world's population. First, we divide the amount of CO2 that can still be emitted worldwide by the world' population. For example, to reach the 1.5° goal, we can still emit 300 billion tons of CO2. We need to take into account that the population of the world is growing, so we do not divide the amount of CO2 by the current population of the world, but instead we divide it by the mean between the current population and the population projected for 2050. 2050 is when most of the countries plan to be carbon neutral. Finally, we divide the remaining carbon budget per person by the number of years left until carbon neutrality should be reached. The calculation of the carbon budget is summed up in the following table. Since Germany has pledged to be carbon neutral already by 2045, the remaining time is shorter and therefore the remaining carbon budget per person and year is a bit higher.

You can view this remaining carbon budget per person and year as the average amount of carbon that you can still emit per year until 2050 (or 2045). Probably, your emissions will decrease gradually until you become carbon-neutral. So it is ok if you are still emitting more than your yearly budget at the moment, as long as your annual emissions will sink below your annual budget soon enough.

• Department for Business, Energy & Industrial Strategy, (2020). Greenhouse gas reporting: conversion factors 2020. https://www.gov.uk/government/publications/greenhouse-gas-reporting-conversion-factors-2020

• Gohar, L. K. & Shine, K. P., (2007). Equivalent CO2 and its use in understanding the climate effects

of increased greenhouse gas concentrations. Weather, 62: 307-311. https://doi.org/10.1002/wea.103

• Jahnke, K., Fendt, C., Fouesneau, M. et al. An astronomical institute’s perspective on meeting the challenges of the climate crisis. Nat Astron 4, 812–815 (2020). https://doi.org/10.1038/s41550-020-1202-4

• IFEU Heidelberg, Umweltbundesamt (UBA), 2010. TREMOD (Transport emission model) version

5.1. Data and calculation model; energy use and pollutant emissions of motorized traffic in germany on behalf of Umweltbundesamt (UBA). https://www.bmu.de/fileadmin/Daten_BMU/Pools/Forschungsdatenbank/fkz_3707_45_101_motorisierter_verkehr_bf.pdf

• IFEU Heidelberg, Umweltbundesamt (UBA), 2019. TREMOD (Transport emission model).

https://www.ifeu.de/en/project/uba-tremod-2019/

• Moss, A. R., Jouany, J. P., & Newbold, J., (2000). Methane production by ruminants: its

contribution to global warming. In Annales de zootechnie (Vol. 49, No. 3, pp. 231-253). EDP Sciences. https://doi.org/10.1051/animres:2000119

• Öko-Institut, International Institute for Sustainability Analysis and Strategy (IINAS), 2021. GEMIS

(Globales Emissions-Modell Integrierter Systeme): freely available computer model with integrated database for lifecycle asessments and co2 footprints of energy, resource and transport systems, developed by Öko-Institut, 2012 passed to the International Institute for Sustainability Analysis and Strategy/Internationales Institut für Nachhaltigkeitsanalysen und -strategien (IINAS). http://iinas.org/about-gemis.html

• Umweltbundesamt (UBA), 2021. Umweltfreundlich mobil! Ein ökologischer Verkehrsartenvergleich für den Personen- und Güterverkehr in Deutschland. https://www.umweltbundesamt.de/en/publikationen/umweltfreundlich-mobil

Table Of Content
• 1 General information
What are CO2 e-emissions?
Calculation of your carbon footprint
• 2 Electricity
Defining a share of electricity use
• 3 Heating
Defining a share of heating consumption
• 4 Business trips
Geocoding
Distance computation
Specifica of the modes of transport for business trips
Range categories
• 5 Commuting
Specifica of the modes of transport for commuting
Aggregating to the group's level
• 6 Emission factor sources
ProBas database
Brochure "Umweltfeundlich mobil!"
Greenhouse gas reporting: conversion factors 2020
• 7 Calculation of remaining carbon budget
• 8 References