Mercari’s Positive Impact (Avoided Greenhouse Gas Emissions)

According to the results of calculating the reduction contribution across seven categories, researchers discovered that through Mercari transactions in both Japan and the US, we avoided approximately 690,000 tons of greenhouse gas emissions annually. The categories examined were Clothing, Electronics (computers, tablets, and smartphones), Media (books, CDs, DVDs, etc.), Bags, Shoes (expanded from the Sneakers category included in the calculations through 2024 to cover other shoe-related categories), and Washing Machines (added to the calculations this year).^{2, 3} This is equivalent to the volume of approximately 285 covered baseball stadiums4 or the amount of CO2 absorbed by approx. 79M cedar trees in one year.⁵

Manufacturing a new product generates environmental burden across the various stages of its life cycle, from raw material extraction to disposal. At Mercari, we believe that utilizing secondhand items as alternatives to new ones can contribute to reducing this environmental burden. To quantify this contribution, we calculated the reduction in environmental burden, what we call “avoided emissions,” that occurs when a secondhand transaction on Mercari replaces a new item. For this calculation, we used greenhouse gas (GHG) emissions as our indicator, a common metric for quantifying climate change impact.

We calculate avoided emissions using the life cycle assessment (LCA) methodology. LCA is a method for quantifying the environmental impact of a product or service throughout its entire life cycle, across raw material extraction, manufacturing, distribution, use, and disposal.
We quantify avoided emissions by calculating the difference between two scenarios: scenario 1, in which a consumer purchases a new item, and scenario 2, in which a consumer purchases a secondhand item from Mercari. This calculation is based on the assumption that the secondhand item serves as a substitute for a new one.
Specifically, we first define the system boundary as follows. For scenario 1 (purchasing a new item), we define the GHG emission scope to cover the product’s entire life cycle, from production to disposal. For scenario 2 (purchasing a secondhand item on Mercari), the scope is limited to the distribution and use stages. This is because, by assumption, the emissions from the product’s production and disposal are attributed to the new item. Finally, we calculate the GHG emissions for each scenario and compute the difference to arrive at the amount of avoided emissions.
Recognizing that not every secondhand purchase on Mercari replaces a new one, we also incorporate the concept of a displacement rate into our calculation. This rate represents the proportion of secondhand transactions on Mercari that directly displace the purchase of a new item. It is based on survey data from Mercari users with experience buying or selling items on the platform, aggregated by product type.
These calculation methods were designed by Mercari’s research and development organization, R4D.^{6, 7}

43,000 tons of clothing that is no longer needed is listed on Mercari, finding new value and avoiding waste. This is equivalent to approximately 7.7% of Japan’s annual clothing waste.¹⁰Selling or buying one item of clothing on Mercari helps avoid approximately 9.6 kg of greenhouse gas emissions on average, and it also extends the usage life of each item of clothing by 3.2 years instead of replacing them with new items of clothing.¹¹

Items that people no longer need can find new value through Mercari. Users’ transactions on Mercari contribute to reducing waste and circulating resources.

Mercari is an advocate of the Green Friday¹² movement that originated in Europe and North America, promoting sustainable consumption on the same day as the major sales day Black Friday. We propose fun and easy ways for consumers to enjoy sustainable fashion in collaboration with partner companies primarily in the apparel sector with the aim of reducing waste and realizing a circular economy.
See here for information about Mercari’s past Green Friday initiatives (articles available in Japanese only):
 

1. Avoided GHG emissions for Mercari in the US were calculated in accordance with the numbers used in analyzing data for the Mercari app in Japan (per-category emission factors and user survey results in Japan).
2. The calculation includes secondhand items purchased on the Japan and US Mercari marketplace apps for which transactions were completed from April 2024 to March 2025 in the following categories: Clothing (Women’s Fashion, Men’s Fashion, Babies & Kids); Computers; Smartphones; Tablets; Books; Magazines; Comics & Graphic Novels; CDs, DVDs & Blu-rays; Bags; Shoes (including Sneakers); and Washing Machines.
3.
– The amount of greenhouse gas (GHG) emissions avoided by reusing items in place of buying new items = Amount of GHGs generated by using new items – Amount of GHGs generated by reusing items = (Number of new items equivalent to secondhand items x GHG emissions generated by new items) – (Number of secondhand items x GHG emissions generated by secondhand items)
– The effect of greenhouse gas (GHG) emissions avoided by reusing electronics (extending their product use life) = Amount of GHGs generated by using only new items (baseline) – Amount of GHGs generated by reusing items (R2 scenario) = (Number of devices used in the baseline scenario x GHG emissions generated by new items) – (Number of devices used in the R2 scenario x GHG emissions generated by new and secondhand items)
4. CO2 equivalent to one covered baseball stadium: approx. 2,436 t-CO2 (covered baseball stadium volume: 1.24M m3 = 1.24M kL; 1 mol = 22.4 L = 44 g-CO2; Source: Tokyo Dome https://www.tokyo-dome.co.jp/faq/dome/)
5. From “How Much Carbon Dioxide Do Forests Absorb?” published on the website of the Forestry Agency (available only in Japanese) https://www.rinya.maff.go.jp/j/sin_riyou/ondanka/20141113_topics2_2.html
6. Summary of Mercari user survey
Apparel and Sneakers categories
– Period: January 30 to February 3, 2023
– Target: Users who listed or purchased an item on the Mercari marketplace app in the apparel categories
– Method: Mercari app survey
– Number of respondents: Listers: 18,137, Buyers: 13,696
Electronics category
Period: January 19 to January 25, 2023
– Target: Users who listed or purchased an item on the Mercari marketplace app in an electronics category
– Method: Mercari app survey
– Number of respondents: Listers: 16,174, Buyers: 10,699
Books and music categories
– Period: June 26 to July 2, 2023
– Target: Users who listed or purchased an item on the Mercari marketplace app in a books or music category
– Method: Mercari app survey
– Number of respondents: Listers: 4,264, Buyers: 2,812
Bags category
– Period: March 15 to March 23, 2025
– Target: Users who listed or purchased an item on the Mercari marketplace app in a bags category
– Method: Mercari app survey
– Number of respondents: Listers: 1,187, Buyers: 867
Shoes category
– Period: March 15 to March 23, 2025
– Target: Users who listed or purchased an item on the Mercari marketplace app in a shoes category
– Method: Mercari app survey
– Number of respondents: Listers: 780, Buyers: 1,151
Washing Machines category
– Period: May 17 to May 26, 2025
– Target: Users who listed or purchased an item on the Mercari marketplace app in the Washing Machines category
– Method: Mercari app survey
– Number of respondents: Listers: 509, Buyers: 213
7. The amount of GHG emissions generated from materials and energy used to calculate the amount of GHG emissions cited in this release were based on figures referenced mainly from the “IDEA v3.3” LCI database.
8. CO2 emissions from household air conditioner usage estimated at 0.36kg/h; from the Decokatsu Database published on the Ministry of the Environment’s website (https://ondankataisaku.env.go.jp/decokatsu/decokatsu_db/)
9. CO2 emissions involved in manufacturing and disposing of/recycling a 500ml plastic bottle estimated at 0.119kg/bottle; from page 17 of “Analysis of the Environmental Burden of Using Reusable Drinking Containers, Cups, and Bottles” published on the Ministry of the Environment’s website (https://www.env.go.jp/recycle/yoki/c_3_report/pdf/h23_lca_01.pdf)
10. Calculated based on the number of clothing items listed in the Women’s Fashion, Men’s Fashion, and Babies & Kids categories on Mercari (in Japan only) from April 2024 to March 2025. Figures for weight of apparel were referenced from Ministry of Economy, Trade and Industry data (Source: Ministry of Economy, Trade and Industry “Survey on Measures to Revitalize the Textile and Clothing Industry” https://warp.da.ndl.go.jp/collections/info:ndljp/pid/1621320/www.meti.go.jp/report/downloadfiles/g20523b01j.pdf)
11. In the Ministry of the Environment’s Decokatsu Database, the action of purchasing secondhand clothing online is estimated to reduce emissions by 9.5kg per item, under the assumption that a secondhand dress shirt can completely serve as a substitute for a new dress shirt. Mercari’s calculations cover a variety of types of clothing and take into account how well secondhand items can be used in place of new items by factoring in a displacement rate based on a survey of Mercari users. As such, these calculations are made under different assumptions.
12. Green Friday is a movement that calls for environmentally-friendly sustainable consumption such as treating items more carefully so they last longer. The movement was created in contrast to the famous annual sale day Black Friday (the Friday after America’s Thanksgiving Day, celebrated on the fourth Thursday in November), which is associated with overconsumption. Europe has stood at the forefront of the Green Friday initiative, with numerous events and workshops being held to coincide with Black Friday sales events to provide people with the opportunity to exchange pre-loved clothes and learn how to repair items to prolong their life.