When you buy a second hand item on Sellpy instead of a new one, you save the CO₂ emissions that would otherwise have been generated during the manufacturing process. We estimate the savings by comparing the emissions from producing a new item with the emissions from a second hand item sold via our platform. For second-hand items that are not assumed to replace a new items, we take the replacement rate into account.

To estimate the amount of CO₂ required to manufacture a new item, we first create a representative item for each product category. The emissions for this representative item are based on collected data on material and weight from over 120 000 items across more than 400 product categories, including clothing, accessories, and other textile products. These data provides us with insights about the material composition of previously sold items, such as the proportion of cotton and polyester in denim fabric. We then use emission values per kilogram of material in the manufacturing stage, the item’s weight, and post-production activities to estimate the average CO₂ emissions per representative item. Items listed as new condition and those sold by businesses do not contribute to CO₂ savings.

The replacement rate refers to the probability that purchasing a second hand item on Sellpy replaces the purchase of a newly produced item. This rate is based on responses from a customer survey conducted across several of Sellpy’s markets. In the survey, customers were asked about what item they purchased, why they chose to shop on Sellpy, and whether they would have bought a new equivalent item if it had not been available on our platform. We incorporate the replacement rate into our estimates for both total savings and savings made possible by our sellers.

Our own CO₂ emissions include products and services such as energy consumption for warehouses and offices, the production of packaging materials, internal transport, collection and delivery services, waste management, business travel, employee commuting, and data services. Since the characteristics and conditions of different items affect their emissions, these are reported per item. The definitive climate impact of an item is influenced by factors such as the distance it has been transported, its estimated weight, and the number of items sent in the same bag.

Higg MSI is a tool used to estimate the environmental impact of materials in consumer items. We use data from Higg MSI to estimate the manufacturing emissions for new items. We believe this tool is the best one available, but we continuously work to improve our estimates to better reflect the complexity of reality.