Carbon Calculator methodology

Purpose of the Carbon Calculator

The Carbon Calculator allows users to estimate what the carbon emissions will be for their trip to Scotland. Breakdowns are shown for different category types including transport (to Scotland and around Scotland), accommodation and diet. We aim to supply the user with useful tips on how they can reduce the carbon footprint for their trip and signpost them to further information and organisations they can engage with. The calculator aims to help users investigate where they can make more sustainable choices when travelling to Scotland.

Running carbon count

Our calculator shows a running carbon count so that users can see how their choices at each stage affect their overall score.

Top tip links at each stage

We chose to include ‘top tips’ at each stage of the calculator to give visitors a resource to help them make more sustainable choices in that area.

Travel to Scotland

To calculate transport we used data from the Greenhouse gas reporting: conversion factors 2023 from the British government's Department for Energy Security and Net Zero and Department for Business, Energy & Industrial Strategy. This gave us breakdowns for how much kg CO2e each vehicle used per kilometre. The vehicles on the calculator that used this dataset included petrol, diesel and electric cars, planes, ferries, coaches and trains. We were not able to find specific data for campervans, motorhomes and caravans. However, the government classes private motorhomes as being under 3500kg (source) and using the Greenhouse gas reporting: conversion factors 2023 we were able to use the data it supplies for vans to calculate average values for campervans and motorhomes up to 3500kg. We will explore the possibility of adding in data for caravans and further breakdowns by size in a further iteration of the calculator.

By multiplying this score by the average kilometres travelled, we are able to determine how much kg CO2e was emitted for this journey. We ascertained how many kilometres were travelled by looking at how many hours were travelled, then multiplied this amount by the average km/hour rate per vehicle type.

For the breakdown of flight times, we categorised domestic flights to include 1 hour flights, short-haul to include 2-5 hours and long-haul as 6 hours or more.

Accommodation

To calculate the accommodation score, we used data from the Greenhouse gas reporting: conversion factors 2023 from the British government's Department for Energy Security and Net Zero and Department for Business, Energy & Industrial Strategy which was sourced from the Cornell Hotel Sustainability Benchmarking Index (CHSB) Tool. This gave us the amount of kg CO2e emitted for a hotel room per night. This was based on the HCMI (Hotel Carbon Measurement Initiative) that looked into emissions regarding fuels burnt on site, electricity used on site and any outsourced laundry and refrigerants. We multiplied this rate by the number of nights entered. For further information please see the methodology report that accompanies the Greenhouse gas reporting: conversion factors 2023.

Travel around Scotland

To calculate the emissions of travel around Scotland, we used the same data as the previous section. To make the process simple for the user, we ask only for their main method of transport while in Scotland.

To calculate these emissions, we multiply the kg C02e emitted in an hour with the chosen transport type by the number of days the visitor is staying. We averaged the time spent travelling around Scotland as an hour per day by looking at two popular trips, the North Coast 500 (by car) and journey between Glasgow and Edinburgh (by train). Assuming a car is travelling at 40mph, the 516 miles of the North Coast 500 can be completed in 12.9 hours. Dividing this by 7 (average number of days in which people complete the route), gives an average of 1.8 hours travelled a day. The train journey between Edinburgh and Glasgow is typically 45 minutes (0.75 hours). Adding these two results together and taking an average gave us a result of 1.275 hours, which we rounded to the nearest whole number for our calculations.

Using an average multiplied by the number of days a visitor is here allows us to account for the different lengths trips that visitors may take; and how time spent travelling around can be impacted by the length of a trip, i.e., typically a longer trip will have more travel hours.

Diet

To calculate diet emissions, we used data from the World Wide Fund for Nature (WWF) which gave us data on the average kg CO2e emitted for each dietary type for regular and moderate meat-eaters, vegetarians and vegans. We also used data from a 2014 UK study by Scarborough et al (2014) for additional dietary types including pescatarian and infrequent meat-eaters that were not included in the WWF report. The WWF report uses the DEFRA Family Food Dataset, data on calorie content from the NHS website and a study by Hoolohan et al (2013) to ascertain emissions of gCO2 for each dietary type. The study by Scarborough et al (2014) ascertained emissions from a dataset that contained GHG emissions for 94 food commodities in the UK that had a weighting for the global warming potential of each component gas. The average GHG emissions associated with a standard 2000 kcal diet were estimated for all subjects. This study used a smaller sample size of 65,000 participants from the UK.

Results

We display the results of the Carbon Calculator in CO2e which stands for carbon dioxide equivalent. CO2 only measures Carbon Dioxide. However, CO2e stands for "Carbon Dioxide Equivalent" and measures CO2 as well as other greenhouse gases such as methane and nitrous oxide.

We chose to include emissions per day as well as total emissions to make the results fairer on those who are limited in their travel to Scotland options. If a visitor were to stay for longer, that evens out their emissions in the different categories, giving them the opportunity to have a lower daily emissions score.

We have chosen to signpost users to environmental charities in Scotland that they may wish to get involved with. The projects have been chosen as they cover different aspects of biodiversity (seas, trees, and wildlife). We aim to add more of these in the future to give our visitors the opportunity to get involved with a project they are passionate about, as well as rotate the organisations featured to ensure equal and varied exposure of biodiversity projects.

Limitations

We were not able to add in calculations for specific accommodation types when looking at the emissions associated with lodging, as there was not sufficient data to assess this. Instead, we used emissions from the average hotel stay for each accommodation type as detailed above. These calculations translate as they calculate metres of floor space and average heat and water consumption, which is the same for any room.

Our ‘Getting Around Scotland’ section uses an average in the calculation and an assumption of travel behaviours, rather than looking the specifics on individuals’ journeys. We use this estimation as we are not able to accurately measure the distance travelled by each user within the country. This is due to insufficient knowledge on what transport options and distances will be travelled by visitors while they’re here.

When calculating the emissions for cars, we based this on the average car size declared in the Greenhouse gas reporting: conversion factors 2023 which draws an average from small, medium and large sized cars. We chose not to categorise cars by size, to reduce the number of details users would be required to enter on the calculator. If you wish to see a further breakdown for kg CO2e emissions for car size, please see further breakdowns in the Greenhouse gas reporting: conversion factors 2023 report. We will explore the possibility of adding further breakdowns in a future iteration of the calculator.

We currently do not have average rates of CO2e emissions for each category type on the calculator. However, we aim to update this in time when sufficient data has been collected.

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