F.A.Q.

Greentripper specialises in carbon footprint calculations for transport and travel. We regularly review the emission factors (EF) used for the calculator and adapt them, if necessary, once or twice a year, to keep the CO2e calculator up to date and in line with the latest scientific advances for greenhouse gas estimation.

We are trained with the Bilan Carbone® method. Greentripper is mainly based on 2 main methodologies:

• the Bilan Carbone ® approach of ADEME, i.e. the French Agency for the Environment and Energy Management. This semi-public body is recognized worldwide for its tool/method for calculating greenhouse gas emissions known as the Bilan Carbone®. ADEME is one of the pioneers in the calculation of greenhouse gases and their conversion into CO2e equivalent according to the global warming potential (GWP), i.e. the contribution to the greenhouse effect.

• DEFRA, The Department for Environment Food & Rural Affairs (GOV.UK) which provides conversion factors for organizations and individuals to calculate greenhouse gas (GHG) emissions from a range of activities, including energy use, water use, waste disposal, recycling, and transportation activities. It is a standard that complies with the GHG (Greenhouse Gas) protocol.

Greentripper specialises in calculating the carbon footprint of transport and travel. We review our emission factors (EF) and update them one to two times per year, keeping our CO2e calculator aligned with the latest scientific insights on greenhouse gases.

These emission factors are determined through calculations based on:

• The impact of passengers travelling by plane, bus, boat or train
• The impact of cars, campervans and two-wheelers
• The impact of visitors on accommodation and meeting rooms
• The impact of travellers on their activities and food choices

Greentripper primarily relies on two recognised methodologies:

• The Bilan Carbone© approach from ADEME, the French Agency for Ecological Transition. This semi-public organisation is globally recognised for its greenhouse gas calculation method. ADEME is one of the pioneers in calculating greenhouse gas emissions and converting them into CO2e based on Global Warming Potential (GWP).
• DEFRA, the UK Department for Environment, Food & Rural Affairs, which provides conversion factors enabling organisations and individuals to calculate greenhouse gas emissions across a range of activities — including energy use, water consumption, waste disposal, recycling and transport. This methodology is compliant with the GHG Protocol.

The calculations performed with the Greentripper tool give you insight into your greenhouse gas (GHG) emissions in CO2-equivalent. These results aim to provide a solid general understanding of your emissions, while acknowledging that no current methodology can guarantee absolute precision. A degree of uncertainty always remains inherent in these calculations.

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All modes of transport (bus, train, tram, car, boat, plane) emit CO2e. Every time you travel, CO2 is released into the atmosphere. CO2 is a greenhouse gas produced when fossil fuels such as oil, gas or coal are burned. The more CO2 in the air, the warmer our planet becomes.

This warming already has and will continue to have consequences at both regional and global scale: shifts in temperature, more frequent and intense extreme weather events, declining resources such as fresh water, and rising sea levels. If greenhouse gas emissions do not decrease significantly in the coming years, many areas could become uninhabitable. Global warming is inevitable, but we can still limit it by reducing greenhouse gas emissions.

According to a 2019 study by the UNWTO (the World Tourism Organization), transport-related greenhouse gas emissions from tourism accounted for 5% of total human-caused emissions in 2016, and are projected to rise to 5.3% by 2030.

In May 2018, researchers from the University of Sydney published a study showing that the global impact of tourism represents 8% of worldwide greenhouse gas emissions. The study, published in Nature Climate Change, covers transport, accommodation, food and shopping by travellers.

Supporting climate projects is a voluntary and concrete way to take responsibility for your climate impact and CO2e emissions. By acting on 100% of your CO2e footprint, you enable us to support climate projects that not only prevent CO2e emissions but also generate broader sustainable socio-economic benefits. These projects would not exist without your support and without the voluntary carbon market. The projects proposed by Greentripper meet the highest international standards, to ensure your contribution makes a real difference.

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Explore the projects we support on our Give Back page, or get in touch with the Greentripper team at info@greentripper.org

1. A shift towards sustainable travel

Travellers and businesses are recognising the need for change, but many don't know where to start. Studies highlight:

• 75% of travellers want to adopt more sustainable travel habits (Booking.com Sustainable Travel Report 2024).
• 70% of travellers feel overwhelmed and unsure where to begin or find relevant information (Expedia Group Sustainable Travel Study 2022).
• 60% of corporate travel buyers cite the lack of transparent data access as a major challenge (Amex Global Business Travel Stay Green Report 2022).

2. Regulations

The world is changing, and businesses are being called to act. From 2025, the largest companies will be required to report on their environmental and social impacts under new regulations, including the Corporate Sustainability Reporting Directive (CSRD). Smaller companies will follow in the future. These rules will push organisations to measure, reduce and communicate their carbon footprint like never before.

3. The urgency for the travel sector

The travel sector is particularly vulnerable to the effects of climate change, and its future depends on urgent action. While other industries are successfully cutting their emissions, tourism continues to grow.

Despite technological advances improving the sector's efficiency, these gains are not enough to keep pace with the constant rise in demand. The direct consequence is a growing carbon footprint for tourism, making it one of the hardest sectors to decarbonise.

Acting now is not optional. It is not just about preserving the economic viability of tourism  it is about limiting its climate impact and protecting the ecosystems and communities that bear the consequences. By adopting more responsible practices today, we can reduce the carbon footprint of travel and ensure that future generations can still explore the world without exhausting it.

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A carbon credit is equivalent to one tonne of carbon dioxide reduced or absorbed by a climate project.

The choice of mode of transport has the biggest influence on the carbon footprint of your travels. Flying generates the most emissions; therefore, it is preferable, as much as possible, to favour alternatives such as public transport or carpooling. If flying is unavoidable, try to reduce the number of air trips by travelling less frequently, avoiding domestic flights, choosing destinations closer to home and extending the length of your stays. Every little bit counts, whether before, during or after your trip.

Greentripper uses the DEFRA methodology to calculate the carbon footprint of air travel (kg CO2e per passenger per km). It takes into account travel class, flight distance, stopovers, Well-to-Tank impact and the radiative forcing effect. All greenhouse gases are converted into CO2-equivalent. Emission factors are regularly updated and reviewed at least once a year.

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When you contribute for 100% of your CO2e emissions from accommodations and transportation (car, plane, etc.), you make it possible to reduce, sequester, or avoid the same amount of CO2e emissions in a climate project as those emitted during your journey.Greentripper guarantees that your contribution for one tonne of CO2e corresponds to:

• one tonne of CO2 that is reduced or avoided through a certified climate project in a developping country
• or one tonne of CO2e that is sequestred in a sustainable project in Europe.

With the carbon contribution, you give us the opportunity to work with NGOs and communities to collectively mitigate climate change and participate in sustainable socio-economic development.To ensure that your contribution makes a real difference in favour of our climate, Greentripper only supports climate projects that meet the highest requirements.

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Yes, absolutely! At Greentripper, we believe that everyone should have the opportunity to take part in the climate transition. Greentripper offers solutions to SMEs across all sectors to help them act on the carbon impact of their business travel. When it comes to the tourism sector in particular, small and medium-sized enterprises represent around 80% of the industry, giving them a unique ability to inspire positive change and lead the transformation towards a more sustainable sector.

We offer a range of solutions tailored to travel, designed to fit all budgets and workflows.

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GHGs are all the gases responsible for global warming: they absorb part of the sun's rays by redistributing them in the form of radiation within the Earth's atmosphere, a phenomenon known as the "greenhouse effect". More than forty greenhouse gases have been identified by the Intergovernmental Panel on Climate Change (IPCC). CO2 is the main greenhouse gas of human origin generated in particular during the combustion of fossil fuels (oil, coal) and biomass.

• Carbon contribution with Greentripper is reliable, fast and easy.

• Greentripper only supports certified climate projects in developing countries and environmental projects in Europe that meet the highest requirements. We guarantee that your investment will be properly allocated and that it will actually contribute to solving the pressing problems related to global climate change. Greentripper is audited by Forum Ethibel (see "Can I trust Greentripper with my carbon contribution?")

• Greentripper is an initiative of CO2logic, a reliable and trustworthy organization with more than 15 years of experience in climate consulting and project development for the climate.

• You support projects in developing countries and Europe, which are in line with the United Nations Sustainable Development Goals (UN SDG’s). Your contribution does not only bring environmental benefits, but also socio-cultural and economic benefits.

Reducing your emissions as much as possible is the absolute first step. But however hard we try, some emissions are simply unavoidable. That is where certified climate projects come in. They give you the opportunity to take responsibility for those unavoidable emissions while contributing to global solutions. They align with the Sustainable Development Goals (SDGs), addressing major challenges such as poverty, inequality and environmental degradation. By supporting these initiatives, you not only help avoid or sequester CO2e emissions, but also contribute to positive outcomes for ecosystems, communities and local economies.

At the same time, we need to change our travel behaviour. Simply supporting climate projects for your emissions does not solve the underlying climate problem and it also makes us dependent on climate projects that are themselves vulnerable to climate change. It is one part of the solution while we wait for other alternatives, but it remains an important element today if we want to reach our global climate goals and achieve net zero by 2050. Reducing your emissions is the first step; supporting climate projects is the second, for the remaining unavoidable emissions. It is an and-and story.

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Yes, Greentripper provides a certificate for every carbon contribution. These contributions are audited annually by our external partner, Forum Ethibel. They ensure that for each tonne of CO2-equivalent you contribute, one tonne of CO2e is reduced, avoided or sequestered in one of the supported climate projects. Greentripper's services can also help you work towards sustainability labels such as Travelife or CERTA.

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There are several types of greenhouse gases, not just carbon dioxide: any type of greenhouse gas emission can be transposed into CO2 equivalent. Knowing that each type of greenhouse gas has a more or less significant global warming potential compared to CO2, in order to know the equivalence of a ton of greenhouse gases in carbon credits, a specific coefficient must be applied to the gas in question to convert the ton into a ton of CO2 equivalent. This makes it possible to compare the contribution of these different gases to global warming and to take these gases into account in the efforts to reduce the climate impact of an organization or a product.

Every year, Forum Ethibel, an independent external auditor, conducts a comprehensive audit of all CO2e contributions made by Greentripper for its climate partners, including travellers, travel professionals, companies and organizations. This external audit ensures with certainty that 100% of the CO2e volume you have contributed to Greentripper is exclusively dedicated to your preferred project.

When you contribute to Greentripper's projects, you get a certificate that guarantees that every tonne of CO2e for which you have financially contributed is reduced, sequestered or avoided in the project of your choice.

Once the project certification is issued, every tonne of CO2e avoided/sequestered is accounted for and traceable. This process is called the allocation of carbon credits. Each carbon credit is one tonne of carbon dioxide avoided, reduced or absorbed by a climate project. These credits are called "Verified Emissions Reductions" (VER). The monitoring is verified by internationally recognised independent carbon offset or contribution auditors, such as DNV, TÜV or SGS. The auditors are appointed and inspected by the Gold Standard, for example, or by the United Nations Framework Convention on Climate Change (UNFCCC). These audit offices check whether a project is set up and operates according to a particular set of rules. This set is known as 'standard'.

For your action to support an Act Sustainable project, it is a support for initiatives that act on aspects other than carbon and greenhouse gases. We work with associations, foundations and impact companies that restore local biodiversity, and work on education for sustainable development and on waste reduction.  

For your action at the local level (Act Local), in collaboration with Soil Capital, the climate impact of each farm is carried out and verified in accordance with the requirements of the international standard ISO 14064-2.

Carbon offsetting involves financing projects that reduce, avoid or sequester carbon in order to counterbalance your carbon footprint. A certified carbon contribution means purchasing carbon credits from projects that are certified and developed according to the strictest quality criteria.

At Greentripper, we have made a deliberate choice to replace the word "offsetting" with "contribution" and for good reason. The term "offsetting" suggests that the climate crisis can be resolved through simple accounting measures. Unfortunately, that is not the case. Addressing climate change requires a collective, long-term approach involving every sector.

By using the term "contribution", we acknowledge that our efforts are aimed at making a positive difference, not simply cancelling out negative impacts. The term emphasises our shared responsibility and invites individuals and organisations to play an active role, rather than relying solely on a technical mechanism.

This voluntary approach works best when combined with concrete efforts to reduce your CO2e emissions. It is an and-and story.

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This term refers to all requirements relating to the quality of carbon credits generated by GHG reduction or sequestration projects, requirements defined by recognized organizations that work in consultation with various carbon market players. Compliance with the requirements set out in the standards is ensured by certification bodies that evaluate the projects and issue their compliance opinion.

There are 2 types of international contribution standards that Greentripper works with:

• Gold Standard projects: projects generating carbon credits (VER) corresponding to emission reductions that follow the strict criteria of the Gold Standard Foundation. Gold Standard projects have a holistic approach because in addition to reducing greenhouse gases, they pay attention to the economic, social and environmental impact of the projects. CO2logic works 99.7% (2017 percentage) with VER projects.

• VCS (Verified Carbon Standard): project that issues carbon credits (VCUs), the most widely used standard in the world that has certified more than 1300 Projects that generate more than 200 million tons of carbon credits.

In both cases, the project must demonstrate that it contributes to at least three SDGs (Sustainable Development Goals).

Greentripper issues a guarantee certificate that includes a unique certification number. Each year, Forum Ethibel, an independent third-party auditor, conducts a comprehensive audit of all CO2e contributions made by Greentripper for its partners and travellers. This external audit ensures that 100% of the CO2e impact for which you contributed is exclusively dedicated to your favorite project.

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For more information, check out our guarantee page.

The greenhouse gases taken into account include:

• Vehicle manufacturing, using emission factors from Base Carbone 2022 (kg CO2 per vehicle per km)
• Well-to-Tank (WTT):
  • For diesel, petrol and LPG, emission factors are sourced from Base Carbone 2022 (kg CO2 per vehicle per km)
  • For electric and plug-in hybrid vehicles, the EF is based on the country and its energy mix (IEA database)
• Fuel combustion: for combustion engine vehicles, emissions depend on fuel consumption (litres per 100 km). The emission factor source is Bilan Carbone® (kg CO2e per litre)
• Taxis follow the DEFRA methodology for combustion and Well-to-Tank impact

To calculate CO2e emissions, the following inputs are required:

• Fuel type (diesel, petrol, LPG, electric, hybrid, mild hybrid, plug-in hybrid or taxi)
• For electric/plug-in hybrids: electricity source (country and green/grey)
• Fuel consumption or vehicle model for an average consumption estimate (small, medium or large) in l/100 km or kWh/100 km
• Distance travelled (km)

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To understand this properly, it helps to first define the term 'carbon neutrality'. Carbon neutrality is a scientific concept defined by the IPCC (Intergovernmental Panel on Climate Change) as: the situation in which human-caused greenhouse gas emissions are balanced by human-led removals over a given period. It is about striking a balance between all human-caused emissions on one hand, and what can be absorbed by carbon sinks such as forests and soils, or by carbon capture and storage technologies on the other.

ADEME advocates for a long-term vision and daily action to contribute to the goal of territorial or global carbon neutrality. Individual organisations are not "carbon neutral" and cannot become or claim to be.

That is why Greentripper has made a deliberate choice to stop using the term 'CO2e-neutral' in relation to travel climate contributions. We firmly believe that 'CO2e-neutrality' only makes sense in a global context: as a contribution to collective carbon neutrality and only when significant efforts have already been made to reduce your ecological footprint upfront. A climate contribution is then the last resort for emissions that truly could not be avoided.

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No, here's why.

What is the EU ETS?

The EU Emissions Trading System (EU ETS) was set up in 2005 as the world's first international emissions trading system, and is now in its fourth trading phase (2021–2030). It is essentially a market-based mechanism for putting a price on carbon. It sets an absolute limit (or cap)on the total amount of greenhouse gases that covered entities can emit each year. This cap decreases over time, so that total emissions gradually fall.

Under the EU ETS, regulated entities buy or receive emissions allowances, which they can trade with one another as needed. At the end of each year, they must surrender enough allowances to cover all of their emissions. The sectors currently covered include power and heat generation, energy-intensive industries, and aviation within Europe.

What is changing for aviation?

On 14 July 2021, the European Commission adopted a series of legislative proposals outlining how it intends to reach climate neutrality in the EU by 2050, including an intermediate target of at least 55% net reduction in greenhouse gas emissions by 2030.

For aviation specifically, the Commission proposes to gradually phase out free emissions allowances and move to full auctioning by 2027, creating a stronger price signal to drive emissions reductions. The total number of aviation allowances will be capped at current levels and reduced annually by 4.2%. The EU ETS currently applies only to flights between airports within the European Economic Area (EEA). For international flights, the Commission proposes to implement the global Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA).

Why these measures are still limited

These EU ETS and CORSIA measures are a step in the right direction, but they remain limited in scope:

1. No obligation yet for the first phase (2024–2026). CORSIA only becomes mandatory from 2027 onwards.
2. Only excess emissions are covered. They only act on emissions above 2020 levels, meaning they don't cover 100% of CO2 emissions, but only a fraction.
3. Only CO2 is counted. Other greenhouse gases are excluded, and the radiative forcing effect (which roughly doubles the climate impact of aviation) is not taken into account. Emissions from source to reservoir are also not included.
4. International flights only. All emissions from domestic flights fall outside the scope of these schemes.

This is precisely why your voluntary climate contribution through Greentripper remains meaningful and complementary, it goes further than what regulations currently require.

Greentripper classifies trains (regional trains, night trains, main line and high-speed trains, Eurostar, Thalys, Railjet ÖBB, ICE) with specific CO2e emission factors (EF) in g CO2e per passenger per km. The EFs used come from ADEME's Base Empreinte® for regional, main line and high-speed trains, and from company-specific emission factors for private high-speed rail operators. Updates are sourced from DEFRA, SNCF, Eurostar and scientific studies. To calculate emissions, users provide the distance or travel time, train type, country and number of passengers.

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The cost depends on your carbon footprint. Contributions to certified climate projects are calculated per tonne of CO2-equivalent (CO2e). The price per tonne varies depending on the project type, certification label, scale and location. To ensure full transparency, you receive a guarantee certificate for every contribution. Additionally, Forum Ethibel conducts an independent annual audit confirming that 100% of CO2e contributions made through Greentripper are fully allocated to the project of your choice.

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For metro and tram travel, Greentripper uses the carbon calculation methodology of STIB (Brussels public transport). The emission factors are of the same order of magnitude as the DEFRA factors (in g CO2 per passenger per km). To calculate CO2e emissions, users provide the distance (in km) and the number of people travelling.

Thanks to your carbon contribution, we also strengthen the Sustainable Development Goals (SDG’s) in developing countries. Indeed, the climate projects with which CO2logic and Greentripper work are located in developing countries, which allows local populations to combine socio-economic development and CO2e emission reduction on a global level.

Greentripper classifies campervans and vans into three vehicle types, based on real data from campervan rental companies. For emissions from fuel consumption (kg CO2e per litre), indirect upstream emissions (kg CO2 per vehicle per km) and vehicle manufacturing impact (kg CO2 per vehicle per km), we use emission factors from Base Empreinte® 2023. Users provide the distance and the type of campervan.

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Greentripper uses DEFRA emission factors for coach and bus travel (kg CO2e per passenger per km), taking into account both direct emissions and Well-to-Tank (WTT) emissions. Users provide the bus type, number of people, distance and whether the trip is one-way or return. On request, Greentripper also offers more detailed calculations based on vehicle occupancy rate — for example, in cases where a vehicle has been privately chartered.

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Greentripper has developed its own cruise emissions calculation, based on surveys, articles and a life cycle analysis by Morten Simonsen (Western Norway Research Institute). It includes environmental effects during navigation and the 'hotel mode' effect, which accounts for an average of 30% of total emissions. Users provide the number of cruise days and the number of travellers to calculate CO2e emissions. On request, Greentripper also offers more detailed calculations based on vessel size, actual travel distances and occupancy.

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Greentripper calculates the environmental impact of various accommodation types (kg CO2e), including hotels (2 to 5 stars), bed & breakfasts, seasonal rentals and second homes. For hotels, it relies on GreenView, which takes into account the energy mix per country. For other accommodation types, it draws on ADEME estimates. For accommodation with a recognised ecological approach and a green label, Greentripper estimates a 20% reduction in carbon footprint per night compared to equivalent accommodation without reduction efforts. Users provide details such as accommodation type, country (for the energy mix) and number of occupied rooms per night.

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Greentripper relies on a range of sources for the carbon footprint of activities:

• For motorised activities (helicopter, sightseeing flights, safari and motorised boat), emission factors (kg CO2e per litre of fuel) from Base Empreinte® 2023 are used. Average fuel consumption is sourced from various blogs and articles.
• The impact of a festival day is based on a study by climate consultancy CO2logic.
• The impact of a ski day comes from a study conducted by Utopies, a sustainability consultancy.
• The impact of a hot air balloon was calculated by climate expert Sami.
• Non-motorised and cultural activities are considered to have zero CO2e impact. If these activities require motorised transport to reach them, that transport should be calculated separately (for example, a snorkelling trip that requires a small motorised boat, or a museum visit by coach).

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For the carbon footprint of food, Greentripper relies on emission factors from Base Empreinte® 2023. The traveller selects the general type of meal (vegetarian, mixed, red meat, fish, etc.), the number of days and the number of people.

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Planes, cars and other modes of transport use energy to reach their destination. This energy comes from burning fossil fuels, which releases CO2 and other greenhouse gases that contribute to climate change. To give you a sense of scale, 1 tonne of CO2e is emitted by:

• A single trip from Brussels to New York in economy class
• 6,000 km driven by car
• 336 non-vegetarian meals

One tonne of CO2e could be visualised as one fifth of an Atomium sphere, or a hot air balloon with a volume of 200 m³.

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There are many types of greenhouse gases, not just carbon dioxide. Every type of greenhouse gas emission can be converted into CO2-equivalents, since each gas has a greater or lesser global warming potential compared to CO2. To convert a tonne of greenhouse gas into carbon credits, a specific coefficient is applied to translate it into a tonne of CO2-equivalent. This makes it possible to compare how different gases contribute to global warming, and to account for them in an organisation's or product's efforts to reduce its climate impact.

In the Greentripper calculator, we take into account multiple greenhouse gases (not just CO2, but also CH4 and N2O) all converted into CO2-equivalent. That is why we express results in CO2-equivalents rather than CO2 alone.

We also account for the radiative forcing effect caused by the contrails visible behind aircraft during flight.

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