The purpose of this endpoint is to provide the cradle-to-gate footprint of an item, and the carbon savings achieved as a result of renting or buying the item used
All inputs, outputs and defaults can be seen in the Convert goods and services technical API docs.
Note that this endpoint converts items that can be linked to GPC brick codes. Services, which cannot be linked to GPC brick codes, are covered by the Convert Finance endpoint, where their footprint is specified by their price.
Inputs
Required input fields:
- Unique item identifier: GPC code or item name (All valid GPC codes are listed in the technical documentation)
- Purchase type:
- None (returns just the footprint of an average item of this kind)
- Buying used
- Renting
- Coming soon: repairing; recycling
Optional input fields:
- Number of items
- Price of the item
- Duration of the rental period
- Business model: Online or Physical
- Weight of the item
Outputs
The endpoint returns the cradle-to-gate footprint of producing a new item(s) of the type specified, and the savings associated with the purchase type. For example, if the item you input is a t-shirt, and the purchase mode is buying used, you are returned the footprint of producing a t-shirt and the achievable savings from buying it used.
When multiple items are selected, the order of the output (cradle-to-gate footprint of an item) matches the order of the input items. The unique item identifier inputed (GPC code or string) is also returned.
Calculations and sources
Buying used
When buying an item used, we assume that the used item displaces the need to buy a new item. However, we recognize that this isn’t always a one-to-one trade-off. A used item might have a shorter lifespan than the corresponding new item. Additionally, used items are typically cheaper and often have lower perceived value, so a consumer might choose to purchase more of them.
The concept of a replacement rate is how many new items a used item replaces. Inspired by the model applied in Thomas et al. (2010), we use the ratio of the used price to the new price as a proxy for the replacement rate. The price data is obtained from online shopping websites - for Norway we use Finn.no for used prices and Prisguiden.no for new prices. The median price value of the top 30-50 hits for each type item is used for the calculations. We recognize that this isn’t a perfect solution, but ultimately the replacement rate depends on individual consumption patterns. We do think it is flawed to assume a replacement rate of one, despite this being the de-facto standard in the literature, as this would lead to an inflated footprint savings.
In its simplest format, the savings for buying used is the footprint of the item multiplied by the replacement rate. Additionally, we subtract contributions for transport and preparation for reuse associated with buying the item used, if this data is available. However, studies have shown that these contributions are typically negligible compared to the replacement of the production of a new item.
We have chosen not to include end-of-life (recycling/incineration) emissions in our buying used calculations. This is because, from a life cycle perspective, buying used postpones the end-of-life of the item but does not remove it from the picture indefinitely.
Since we consider the effect of a single item purchased used, we neglect any market effects - that is, how the market might change if the demand for used items drastically increases.
Renting or lending
The calculation method for estimating CO2 savings due to renting is similar to that of buying used, but with a few differences. Since renting involves a shorter duration of product usage, the savings are allocated based on the number of uses during the rental period.
We also incorporate the concept of replacement rate for the renting model. The replacement rate is calculated in the same maner as for buying used. The savings from renting a product are calculated based on the ratio of usage during the rental to the total lifetime uses. We use the duration of the rental to estimate the number of uses.
Repairing
The calculation method for repairing is similar to buying used, but with the addition of accounting for the emissions due to repair. For each item, we identify the most common type of repair action and the emissions associated with that action, based on the work of H. Lauvland (2021) and S. Privett (2018). The final CO2e savings are calculated by subtracting the repair and transport emissions from the emissions saved by offsetting the manufacturing of a new item.
Accounting for transport
The transport emissions are calculated for downstream transportation between the retail store or warehouse and the final customer. We consider two different types of business models: e-commerce and retail/in-store. For each business model, we have defined a transport scenario with default parameters that describe the average distances and the most common mode of transport based on the work of Zampoeri et al (2019).
Based on your selection of the type of store (online or retail), the average distances to the consumer are combined with the multiplier of the most commonly used transport vehicle to estimate the transport emissions. This provides an estimate of the climate footprint associated with the transport of the product to its final destination.
Data sources and disclaimer
For these calculations, a mixture of input-output analysis and life cycle assessment (LCA) is used to estimate the carbon footprint of specific products. We use LCAs, where available, as they provide the most accurate footprint values for specific items. In cases where there are no relevant LCAs, we use CO2e multipliers from input-output analysis along with average pricing data to estimate the footprint of an item. These estimates are then based on the average emissions of the sector of the economy producing this type of product, rather than the emissions from a specific supply chain producing a certain good.
We carefully evaluate each LCA we use to ensure that it has a scope, functional unit and system boundaries that are relevant. However, an LCA is performed on a specific value chain, and may not be representative of the exact supply chain of a given item. The purpose of this endpoint is to give an estimate of the footprint, and the savings that can be achieved by performing actions that increase the circularity of an item, by extending its functional life. We therefore consider LCAs of sufficient quality to be acceptable proxies for a full supply chain analysis of a unique product.
Please note that the data provided by this endpoint should not be used for cross-product comparisons, as we do not have the resolution necessary to compare similar products produced via different supply chains.