When it comes to carbon accounting and decarbonization, here’s why databases based on spending can lead you to a dead-end road.
Some Background
Carbon footprints are the essential prerequisite for setting decarbonization targets and committing to actions to achieve these objectives.
While the determination of Scope 1 and 2 emissions are nowadays considered a very basic and standard procedure, the quantification of emissions throughout the value chain (Scope 3) is still a considerable challenge for most companies, despite the existence of excellent guidance such as the GHG Protocol Scope 3 Standard.
The Challenge
Procurement systems often capture purchase volumes in financial terms and without physical attributes (weight, size, number of pieces, etc.). And even if there are physical attributes available for at least some of the purchased goods and services, organizations often have no access to reliable emission factors to calculate climate impact of these purchases (representing the entire upstream value chain of an organization).
A Quick Fix
The easy fix to this is to simply use the financial numbers (e.g., purchasing volumes in dollars/euros spent) and combine these with so-called environmentally extended input-output (EEIO) tables and models. Monetary input-output tables give insight into the value of economic transactions between different sectors in an economy. They allow users to calculate the added value that each sector contributes to the final output of an economy. Such monetary input-output tables can be easily extended with environment-related information for each sector, including carbon emissions.
Particularly for Category 1 “Purchased Goods and Services” (defined as “Emissions from all purchased goods and services not otherwise included in the other categories of upstream Scope 3 emissions” by the GHG Protocol), many are using this approach. Say a company bought steel for $10 million, then you would apply this figure to an EEIO table for the sector “Primary Iron, Steel and Ferroalloy Products” and get the amount of CO₂ equivalents (CO2e) emitted. When you repeat this process for some of the major materials purchased and add them up, Category 1 of Scope 3 is complete. But is it a smart move?
Heading Down a Dead-end Road
There are several “uncertainties” associated with this approach, such as:
Time:
EEIO data generally represent a period long gone, often from 10 years ago or longer. What about changes in carbon intensity since then? Data uncertainties: Up to a factor of two or even three.
Prices:
The nature of markets is that prices vary over time. Even if updated EEIO tables were available, they could not accurately represent the actual prices you paid for your materials. Steel? Check out the 10-year price history graph for steel below (anywhere from about $235 to $940). Fuels? Same. Lumber? Sugar? Same. Data uncertainties of up to ±80% are not uncommon.