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

The life cycle of a new product generates environmental burden in many steps, from gathering the raw materials to disposing of the product. At Mercari, we believe that utilizing secondhand items in place of new items contributes to reducing this environmental burden. As such, we estimated the amount of purchases of new items that were avoided by transactions on Mercari and calculated roughly how much this contributed to reducing the environmental burden across society. We call this “avoided greenhouse gas (GHG) emissions.”

Life cycle assessment (LCA) is a method of quantitatively evaluating the environmental burden of a product or service throughout its life cycle (production, distribution, consumption, and disposal). We use LCA to calculate avoided emissions.
We define avoided emissions as the difference in greenhouse gas emissions between two scenarios: one in which a consumer purchases a new item, and one in which a consumer purchases the same item secondhand on Mercari. Specifically, we set in scope and calculate 1) the environmental burden of the entire process involved in purchasing a new item and 2) the environmental burden of distribution and consumption for a secondhand item purchased on Mercari. We then calculate the difference between the two. Additionally, not all transactions of secondhand items contribute to reducing the amount of new items produced, so we incorporate the concept of a displacement rate. This rate is an estimate of the percentage of transactions on Mercari in which an item is purchased in place of a new item. The number is calculated based on the results of a user survey.
These calculation methods were designed by our R&D organization Mercari R4D Lab.^{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.

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.