This page is designed to help you calculate how much CO2 was prevented from entering the atmosphere because of things that were shared or reused instead of bought. Other CO2 savings (such as waste reduction, recycling, shared workshop space, material reuse) are not included here.

Emission Factors:

A central part of this CO2 calculation is the emission factor. To calculate the amount of CO2 used to make a new version of a product we need to know how much CO2 was emitted in the making of the constituent parts. There are 3 databases of embedded carbon that we have used to calcuate tool emission factors. Embedded carbon is the amount of carbon released in cradle to gate processes like extraction, transport, refinement and shaping. We have combined these to approximate as best we can to create 12 different emission factors, to cover the make-up of most tools in a tool library inventory. These are shown in the table below. The 12 different factors are a combination of embedded carbon values according to the approximate amounts of that material in that tool type. It’s important to note that we are calculating the CO2 produced in the manufacture of a new tool (which is not purchased because of the existence of the tool library), so we are not concerned with the material composition of older tools.

To create your own emission factors for items that you stock/sell etc, we recommend using the same process - finding emission factors for the contituent parts of the item and combining them in the right ratios

We used 3 different embedded carbon material databases to decide on each emission factors. These are:

• The ICE (Inventory of Carbon and Energy) by Circular Ecology and the University of Bath. https://circularecology.com/embodied-carbon-footprint-database.html
• The Climate Impact Forecast - LCA for startups and impact entrepreneurs. https://climate.impactforecast.org/about/
• Greenhouse Gas Reporting: Conversion Factors 2020, UK Government. https://www.gov.uk/government/publications/greenhouse-gas-reporting-conversion-factors-2020

When there were differences between these databases, we selected the data that most accurately represented our use case for tools, or in some cases combined data for more accuracy. This is noted in the second table below.

Emission factor types

We have selected 12 different emission types, categorised by the materials (one or more) in common tools.

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Emission Factor Values

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With these 12 values and the borrowing history of our tool library, we can calculate our carbon savings for any time period, tool type or member.

The calculation for each tool is:

number of times tool was borrowed instead of bought x weight of tool x emission factor = carbon saved for that tool