The Tokyo Marathon isn’t just about the runners.  We can’t forget all the event volunteers and the spectators who line the streets.  The whole city comes together for the marathon, as it offers 42.195km of diverse experience for everyone involved.
The Tokyo Marathon Foundation, together with ASUENE Inc., will measure and disclose event-related GHG (greenhouse gas) emissions – a first for marathons held in Japan – as part of its commitment to sustainable event management.

The purpose of disclosing environmental impact is more than simply revealing numbers.  We need to identify the primary sources of GHG emissions, formulate an effective strategy to reduce emissions and put forward concrete measures that organizers, participants and stakeholders can implement.  This report will (1) clarify the major contributors of emissions for marathon events, (2) share the results of Tokyo Marathon’s preliminary measurements, (3) analyze sample sustainability reports disclosed by other major international marathons and finally, (4) present a roadmap for decarbonization.

Marathon events involve diverse activities beyond venue operations, such as travel, accommodation, food and beverages, procurement of goods and other consumption behaviors of participants, volunteers and spectators.  In other words, environmental impact cannot be solely determined by organizers’ controllable factors.
Major global marathons are accelerating efforts to measure and disclose GHG emissions and are utilizing those figures to propose reduction targets and strategies.  In line with the global standards, the Tokyo Marathon also aims to disclose carbon footprint information, enhance transparency and initiate reduction actions.

GHG emissions are generally categorized into 3 groups: Scope 1, Scope 2 and Scope 3.
These categories are based on the source of the emissions: direct, indirect or value chain emissions.

・Scope1（direct emissions）：direct emissions by the organizer, such as burning fuel
・Scope2（indirect emissions）：emissions from purchased electricity, heating and other energy consumption
・Scope3（other indirect emissions）：emissions from miscellaneous activities, such as travel, accommodation, procurement of goods, transport, etc.

The largest emissions for marathon events tend to be from Scope 3, which includes travel and accommodation.
For Tokyo Marathon, the results will be analyzed and disclosed based on both scope and activity.

Based on data from Tokyo Marathon 2025, preliminary measurement of GHG emissions for this year’s Tokyo Marathon is estimated at 26,029 t-CO2eq.

GHG Emissions Amount by Scope
Scope1：1 t-CO2eq
Scope2：3 t-CO2eq
Scope3：26,026 t-CO2eq

It’s important to note that most of the GHG emissions are from activities outside the direct control of the organizer (Scope 3), not just from venue management.

Chart 2：Preliminary Emissions Amount（by scope and activity）
Source：ASUENE Inc.

A breakdown of the results by activity has revealed that an overwhelming 88.4% of total emissions came from “Participant, Spectator, Staff Travel,” making it a key area for reduction.

In addition to organizer’s reduction efforts, these numbers show that there is a huge room for improvement in terms of reducing the carbon footprints of “participant, spectator, staff travel” (e.g. distance, modes of transport, etc.).

The Tokyo Marathon is one of the seven premier international marathons, known as the Abbott World Marathon Majors.  That is precisely why it is important for the Tokyo Marathon to follow global standards in quantifying and disclosing GHG emissions and be responsible for transparency and developing concrete reduction measures.

It is important to note, however, that there are various reporting methodologies, using different measurement range and assumptions, so that should be taken into account before comparing the results with other marathons.

The Tokyo Marathon will measure and disclose emissions in accordance with international standards and prepare for the next phase of the journey towards sustainability: reducing CO2 emissions.

The Tokyo Marathon strives to achieve both transparency (reliability) and comprehensibility (leading to action).  We hope to discover the appropriate methodology to accomplish our goal by analyzing the different ways the results are presented by Berlin and Boston Marathons.

6-1.Berlin：Clear and Easy to Understand Visuals

Berlin’s sustainability report makes the overwhelming impact of travel very clear.  There is a breakdown by modes of transport, which may encourage participants to rethink their choice of travel in the future to minimize the impact.

Chart 4：Berlin Disclosure Report（includes breakdown of modes of transport）
Source：BM24_Sustainability_Report_ENG

6-2. Boston: Detailed Disclosure with High Transparency, but Very Technical

Boston’s sustainability report has a very detailed breakdown by categories and is highly transparent.  However, it is very technical in nature so there is room for improvement to make it easier for participants to take in all the information.

Chart 5：Boston Disclosure Report（includes detailed breakdown by categories ）
Source：SE_BAA_2024ESGReport_Final

At Tokyo Marathon 2026, approximately 39,000 runners are expected to run the 42.195km course, covering a combined distance of about 1.645 million kilometers (equivalent to circling the Earth approximately 41 times), using purely human power.  If the same distance were traveled by gasoline-powered vehicles, it would generate an estimated 230t-CO2.  It can be said that running is inherently one of the lowest-impact forms of mobility.
However, transportation used by the runners to participate in the marathon (airplane/train/car/bus etc.) and the distance traveled greatly affect the amount of GHG emissions. Our preliminary measurements show that “travel” is the biggest source of emissions, signifying that the organizer, the city and participants can all play a part in making better travel choices that would lead to reduced carbon footprint.

Chart 6：Running for the Planet（GHG Emissions by Transportation）
Source：ASUENE Inc.

Our Small Steps Today Create Big Changes Tomorrow

The true magic of the Tokyo Marathon is that it brings together the runners, the supporters and the spectators – the entire city of Tokyo.  Our decision to begin measuring and disclosing GHG emissions marks our dedication and commitment to passing on this spirit of unity.

The Tokyo Marathon Foundation, together with ASUENE Inc., will work towards meaningful change and strive for more sustainable event management through data visualization.

Running is not only beneficial for health but is environmentally-friendly as well.  And by consciously choosing sustainable alternatives, it is possible to reduce our carbon footprint.  Each individual choice, made by runners, spectators and supporters alike, can contribute to creating a more sustainable Tokyo Marathon.

In 2026, the Tokyo Marathon will focus on data collection, improving the accuracy of the measurements and establishing a reliable baseline.  From 2027 onwards, the focus will expand to implementing effective reduction measures and promoting behavioral changes.  Furthermore, we plan to pursue mobility-related reduction measures and carbon offsets as well as boost recycling and upcycling efforts.  Additionally, we will continuously disclose not only the calculation results but also the environmental effects (quantified impact) generated by reduction measures, thereby enhancing transparency and Plan-Do-Check-Act cycle.

2026 will be the year of quantifying impact and the years that follow will be of reducing impact.   We will ensure that our efforts lead to actionable improvements.