Fashion Footprint Calculator Methodology and Sources 

thredUP partnered with 3rd party life cycle assessment specialists Green Story Inc. to measure the footprint of garments under both linear and secondhand use systems in terms of carbon dioxide (CO2) emitted, energy, and water consumed for each wear. The impacts and savings compared to linear systems are estimated based on the independent life cycle assessment (LCA) study conducted by Green Story Inc. For the data, Green Story leveraged peer-reviewed studies, verified datasets, primary operational data from thredUP and supply chain databases to analyze each garment category. Consumer surveys were also performed to analyze consumer behavior towards the usage and disposal of clothing types, including the efficiency of the reuse of secondhand garments by examining the displacement rate. For example, the surveys found that not every secondhand garment purchased completely replaces a new purchase, this only happens 72% of the time. 

Question 1 

How often do you buy clothing?

Explanation: 

This question is designed only to gather data on how many times a consumer shops (online and in-store) in a year for apparel. There is no CO2 value associated with the number of trips yet. The number of shopping trips are used to calculate the transportation and packaging impact of buying clothes in a year. 

Data 

Average number of apparel shopping trips per year by women in the US is 41. 

Calculation: As per consumer survey, average annual total purchases by consumer is 1193, and average basket size is 2.874, so the average trips required are total purchases/ basket size.  

Sources 

1. Okafor, C. C., Madu, C. N., Ajaero, C. C., Ibekwe, J. C., Nzekwe, C. A., Okafor, C. C., … & Nzekwe, C. A. (2021).  Sustainable management of textile and clothing. Clean Technol. Recycle, 1, 70-87. 
2. Measuring Fashion. Environmental Impact of the Global Apparel and Footwear Industries Study. Quantis International. 2018. Tech. rep 
3. thredUP consumer survey conducted with Green Story (2022) 

4. Statista article 

Additional tip source:

Ellen MacArthur Foundation: A New Textiles Economy 

Question 2

How many items of clothing do you buy in a year?

Data and Explanation 

The impact for each clothing type is based on detailed modeling done for thredUP by Green Story Inc.

The average product weight is 258 grams or 9.1 oz, based on the product distribution of products sold on the thredUP platform. 

Sources 

1. thredUP 2022 Comparative Life Cycle Assessment (LCA) of Resale vs Linear Clothing Systems. Green Story Inc.  
2. Measuring Fashion. Environmental Impact of the Global Apparel and Footwear Industries Study. Quantis International. 2018. 
3. Estimating the Carbon Footprint of a Fabric 

Question 3

How do you purchase your clothing?

Data and Explanation: 

This question is used to understand the online vs in-store shopping behavior of the consumer. Latest statistics for the share of online apparel shopping in the US stands at 46.0% in 2020 up from 34% in 2018. Based on the user inputs for each mode of apparel shopping and total purchases in a year, we can calculate the transportation and packaging impact of all such purchases. 

The above table was created using the below data:

Question 4

What percent of your clothing purchases do you return?

Data & Explanation: 

About 25% of returned items are never sold and end up in landfill. This is a major impact of return and the penalty has to be considered. This penalty is calculated on the number of items returned and not on total return trips. Return transportation is calculated based on the number of purchases and not on the number of items bought. Usually, people would make one combined return for all the items they want to return from that shopping trip. Items bought online whether via express or standard way are returned via standard shipping. And items bought in store are returned in store. In most cases, packaging received during purchase is reused for the return, so no additional packaging is required, hence no packaging impact is considered for return.

Sources

1. Dimitri Weideli Environmental Analysis of US Online Shopping, Master Thesis 
2. GHG Emissions Factors EPA
3. How Consumers and Retailers Can Reduce Returns 

4. Statista article 
5. thredUP 2022 Comparative Life Cycle Assessment (LCA) of Resale vs Linear Clothing Systems. Green Story Inc.  
6. CNBC Growing Online Sales Means More Returns and Trash for Landfills 

Question 5

What percent of your clothing purchases are secondhand?

Data and Explanation 

The credit for each clothing type is based on detailed modeling done for thredUP by Green Story Inc. 

Sources: 

1. thredUP 2022 Comparative Life Cycle Assessment (LCA) of Resale vs Linear Clothing Systems. Green Story Inc.  
2. Statista article 
3. Statista: Breakdown of average U.S. consumers’ closet as of 2007-2028, by purchase channel 

Question 6

How many loads of laundry do you do per month?

Data and Explanation

Calculated the number of home laundry cycles in a year by multiplying no of times in a month with 12 (number of months in a year). The credit associated with laundry cycles based on done for thredUP by Green Story based on U.S. laundry data. 

Question 7

Tell us about your laundry habits:

Data and Explanation 

Washing: 

• Based on the choices, we assigned the carbon footprint to washing and drying steps as per below table. 
• Multiplied the total with the number of laundry cycles in a year. 

Carbon footprint per person load based on options (1/4th of household load) 

More laundry info: The average laundry weight is 6.4 kg. We have taken 1/4 impact of full load to calculate personal impact  assuming a family of 4.

Drying: Average electricity use in kWh per load per drying cycle is taken as 4.5 kWh4 

Question 8

How many items do you dry clean each month? 

Data and Explanation

Based on the number of items of dry-cleaned month, calculated number of items dry cleaned in a year (multiplied by 12 months in a year). Multiply the total items with dry cleaning carbon footprint of 1 item. 

Per apparel Dry-cleaning energy impact:

Dry cleaning with green solvent (GreenEarth®) reduces the toxicity of the solvent compared to the most common dry cleaning solvent (PERC) but requires more energy to clean the apparel and collect the solvent. The dry cleaning footprint does not include energy for the solvent manufacture. The energy required for different dry cleaning  methods is provided below, the CO2 impacts are taken as average from these 

Sources for questions 6-10:

1. Laitala, K., Klepp, I. G., Kettlewell, R., & Wiedemann, S. (2020). Laundry care regimes: Do the practices of keeping  clothes clean have different environmental impacts based on the fiber content?. Sustainability, 12(18), 7537. 
2. Sohn, J., Nielsen, K. S., Birkved, M., Joanes, T., & Gwozdz, W. (2021). The environmental impacts of clothing:  Evidence from United States and three European countries. Sustainable Production and Consumption, 27, 2153- 2164. 

3.Storage Heaters Explained 

4.Do Tumble Dryers Use A Lot of Energy?

5. Yun, C., Patwary, S., LeHew, M.L.A. et al. Sustainable care of textile products and its environmental impact: Tumble-drying and ironing processes. Fibers Polym 18, 590–596 (2017). https://doi.org/10.1007/s12221-017-6957-6

Question 9

How many items do you repair each year? 

Data and Explanation

Repairing an item will increase the lifetime of clothing by 40.3%. The average life of garments is 2.64 years (as per consumer survey). So, by extending the life to another year, 33%  impacts are earned as credit. If a user does not repair anything in a year, no credit is provided.  For repairing X apparels per year, multiply the number of apparel items with credit for repairing 1 item from table below. 

Carbon credit for repairing 1 item: 

1. EPA: Textiles Data 
2. Valuing Our Clothes 
3. Suruj-Zaman, M., Jahan, K., Nisa, F. S., Hossain, R., Hossain, M. S., Khandoker, M. N. H., & Ahmed, T. (2021).  Enlargement of Useful Lifespan of Different Garments by Adopting Refashion. Art and Design Review, 9(1),  1-18. 
4. Gwozdz, Wencke, Kristian Steensen Nielsen, and Tina Müller. “An environmental perspective on clothing consumption: consumer segments and their behavioral patterns.” Sustainability 9.5 (2017): 762. 5. Secondary Material and Recycled Textiles (SMART). Donate, Recycle, Don’t Throw Away Infographic. 2019, Donate, Recycle, Don’t Throw Away Infographic.

Question 10

 How do you dispose of your clothing? 

Data and Explanation 

Based on the option selected assign an annual CO2 credit or penalty as per the table below Use table below 

Annual impact of each pathway 

Estimated amount of clothing disposed by Americans per year is 81 pounds or 37 kg per year1. Based on research below are stats for GHG emissions from landfill disposal and recycling pathways2,3 

Sources

1. Huff Post article 
2. EPA WARM data 
3. Advancing Sustainable Materials Management: 2014 Fact Sheet, US EPA 
4. thredUP 2022 Comparative Life Cycle Assessment (LCA) of Resale vs Linear Clothing Systems. Green Story Inc.  
5. Here’s where your donated clothing actually ends up 

Additional tip source:

1. 1 in 2 people throw their unwanted clothes straight in the trash. 2020 thredUP Consumer Survey 
2. 36 billion clothing items are thrown in the trash each year, 95% of which could be reused or recycled. EPA Clothing and Footwear Waste Estimates

Results Page

Average number of shopping trips in a year: 41

Average garments purchased in a year: 119 

Average number of items donated or resold: 148

Average percent of in-store trips: 54%

Average percent of online purchases with standard shipping: 32.2%

Average percent of online purchases with express shipping: 13.8%

Average percent of returns for online purchases: 26%

Average number of returns for in-store purchases: 9%

Average number of secondhand items in closets: 8% 

Average number of loads of laundry per week per household: 5-6 

Average amount of clothing disposed of each year per person: 81 lbs