Learn all about how we calculate the estimated embodied carbon of an exchange for our reports.
This article is helpful if:
You are an admin wondering how we calculate carbon avoided in our Reports.
You are looking for information on ideas about how to talk about the carbon impact of reuse.
Who can do this?
Only admins will have access to view Reports.
Where is it done?
Carbon avoided is relevant to the following reports:
Background
Embodied carbon refers to the greenhouse gas emissions associated with raw material sourcing, supplier processing, and manufacturing of items. A simple act of reuse via the Rheaply platform reduces the likelihood for unnecessary purchases, thus avoiding the attributed embodied carbon of a new item.
Rheaply was among the first circular economy platforms to report on embodied carbon avoided, utilizing a displacement-based methodology and category-level emissions factors to estimate the embodied carbon not added to an organization’s embodied carbon footprint when they source reused materials. This empowers key individuals at organizations to talk about the impact of exchanging resources as an environmental benefit.
The displacement of new product purchases through reuse helps organizations reduce scope 3 emissions related to purchased goods and services (category 1).
Methodology
Rheaply calculates estimated embodied carbon avoided using a tiered confidence approach, selecting the highest-confidence method available for each item based on data completeness and external availability.
Core Formula
At a high level, embodied carbon is calculated as:
Estimated embodied carbon = carbon factor × weight per unit (kg) × quantity
The way the carbon factor is derived depends on the confidence tier applied.
Rheaply Tiered Confidence Approach
Tier 1: Product-Specific LCA or EPD from Database
When applied:
Exact product data is available.
Method:
Uses listing input fields (e.g., manufacturer, model, description) to:
Search the EC3 database for an exact Life Cycle Assessment (LCA) or Environmental Product Declaration (EPD)
Extracts cradle-to-gate (A1–A3) embodied carbon values directly from the source
Tier 2: Product-Specific LCA or EPD from online sources
When applied:
Exact product data is available.
Method:
Uses listing input fields (e.g., manufacturer, model, description) to:
Search reputable public sources for product-specific LCAs or EPDs
Extracts cradle-to-gate (A1–A3) embodied carbon values directly from the source
Continuously expands a vetted reinforcement list of reputable sources used by AI
Tier 3: Material Decomposition with Manufacturing Estimates
When applied:
No exact LCA or EPD exists, but sufficient product detail is available.
Method:
Identifies the material composition of the asset by:
Browsing public sources
Estimating composition using AI when needed (photo, title, category, description, manufacturer, model, material, fabric, finish)
Assigns material-level carbon factors, starting with the Inventory of Carbon & Energy database
Calculates embodied carbon by summing material contributions based on weight and quantity
Includes manufacturing process emissions (cradle → gate):
Based on an internal review, we found the median manufacturing process emissions to be ~2% of overall emissions. We apply that percentage to the overall emissions for each product in Tiers 3-5.
Tier 4: Material Decomposition with Expanded Sources
When applied:
Inventory of Carbon & Energy database data is insufficient or unavailable.
Method:
Follows the Tier 3 decomposition methodology
Sources at least 1 material carbon factor from peer-reviewed journals, academic papers, and industry publications
Tier 5: Material Decomposition with Expanded Sources
When applied:
Inventory of Carbon & Energy database data is insufficient or unavailable.
Method:
Follows the Tier 3/4 decomposition methodology
Does not return at least 1 component material due to inability to successfully map to carbon factor from either Inventory of Carbon & Energy database or online sources.
Tier 6: Category-Level Factors (Baseline Confidence)
When applied:
Insufficient product or material detail is available.
Method:
Uses Rheaply’s original approach:
Category-level embodied carbon factors
Representative products defined by lifecycle assessment practitioners
Factors are mapped to Rheaply categories based on industry-standard averages
The large majority of embodied carbon factors on Rheaply for Tier 6 were created by WAP Sustainability, a leading Life Cycle Assessment consulting firm. WAP's LCA practitioners developed EC factors using both LCA analysis and EPD data for representative products, and assisted in mapping these factors to the appropriate Rheaply product categories.
Additional embodied carbon factors have been sourced from other industry sources, including the Carbon Leadership Forum and various peer-reviewed papers.
Scope of data
Includes accepted and completed internal offers with weight and category data for internal exchanges, and accepted and completed external offers with weight and category data when your organization is the receiving party.
Includes active, deactivated, and deleted user accounts.
Excludes deleted listings.
Excludes listings with withdrawn and canceled offers.
Key assumptions
Exchanging an item via the Rheaply platform is an instance of reuse.
Reusing an item avoids the creation of embodied carbon associated with manufacturing a new product of the same kind.
Life cycle assessments estimate the embodied carbon associated with a product as they have been produced. The scope of these assessments is from A1-A3 lifecycle stages of a product as defined under ISO 21930 with influence from ISO 14040/14044.
Emissions associated with transportation and distribution phases have not been factored in.
Based on an internal review, we found the median manufacturing process emissions to be ~2% of overall emissions. We apply that percentage to the overall emissions for each product in Tiers 3-5.
Disclaimers and Limitations
This report is in beta. It shows the estimated embodied carbon avoided based on user-generated fields of weight per unit and Rheaply's tiered methodology. Associated emissions factors may not cover all potential categories at this time. Significant variation may occur based on the uniqueness of the listed items, the variability of AI estimations of product composition percentages, and the accuracy of the emission factor for a given material.
This data can be used for:
Estimating a quantitative value for the embodied carbon not added to your organization’s footprint due to reuse on the Rheaply platform.
Assigning a value of "0" to scope 3 carbon accounting for your organization when noting impacts due to reuse within the Purchased Goods & Services category.
This data cannot be used for:
Any claims of offsetting greenhouse gas emissions.
Any claims reducing existing emissions within the purchased goods and services category.
Any claims relating to carbon offsets or carbon credits.
Guidelines for data use
If this data is shared outside of viewing on the Rheaply platform, kindly follow the requirements below:
Values for estimated embodied carbon avoided must be presented separately from scope 3 carbon accounting in a greenhouse gas inventory.
Values for estimated embodied carbon avoided must be presented either as zero impact or as a non-zero value by additionally applying a "worst-case" 40% bounded margin of error to the CO2e avoidance calculation per item.
Sample phrasing for zero impact: [X number] of items in [Y categories] were reused and thus assigned an impact of zero.
Sample calculation using the margin of error: a chair has an embodied carbon value of 27.83 kg CO2e. 27.83 - (40% * 27.83) = 16.70 kg CO2e avoided.
Definitions
Embodied carbon – As defined by our partner, WAP Sustainability Consulting, embodied carbon refers to the greenhouse gas emissions associated with raw material sourcing, supplier processing, and manufacturing.
Embodied carbon emission factors – As indicated by the Environmental Protection Agency, emission factors essentially represent the quantity of emissions released with the activity attributed to the release of emissions (Source: EPA). Rheaply has integrated embodied carbon emission factors as derived from our partnership with WAP Sustainability Consulting. These factors represent the quantity of the emissions released from raw material sourcing, supplier processing, and manufacturing of items.
Carbon dioxide equivalent (CO2e) – According to the EPA, this measure is “the number of kg of carbon dioxide emissions with the same global warming potential as one kg of another greenhouse gas” (Source: EPA). The EPA has a great Greenhouse Gas Equivalencies Calculator to translate C02e emissions into real world examples, like "miles driven by an average gasoline-powered passenger vehicle" or "number of homes' electricity use for one year," to help make this number more approachable.
Global warming potential (GWP) – According to the EPA, the global warming potential of a greenhouse gas is the quantification of “how much energy the emissions of 1 ton of the gas will absorb over a given period of time, relative to the emissions of 1 ton of carbon dioxide” (Source: EPA).
Greenhouse gas – Refers to any gas that has the chemical properties to retain heat and reflect that energy toward the Earth’s surface, contributing to the greenhouse effect and climate change (Source: EPA).