Supply Chain (Scope 3) Greenhouse Gas Emission Factors

CenSA calculates and supplies supply chain (scope 3) GHG emission factors to the UK Department for Environment, Food and Rural Affairs (Defra). Factors for the year 2004 have been published by Defra as part of its "Guidance on how to measure and report your greenhouse gas emissions".



What do these factors mean?
The supply chain emission factors express the total amount of GHG emissions associated with one £ of expenditure on a particular good or service. They are based on a "cradle-to-shelf" life-cycle approach, taking into account emissions along all stages of the production chain. This does not only include material extraction, manufacturing, and distribution but also more indirect processes and activities that take place further up in the supply chain, such as infrastructure provision, machinery, banking and financing, advertising etc. The factors encompass the 'upstream' part of scope 3 emissions as defined by the GHG Protocol. They do not account for emissions from the use of products and from end-of-life processes.

How can these factors be used?
The supply chain factors published by Defra can be used to obtain a broad estimate of the total GHG emissions embodied in goods or services bought by an entity (companies, organisations, households, etc.). The analysis requires three main steps: Expenditure (procurement data) on goods and services have to be converted from actual (purchasers') prices to basic prices by subtracting taxes and distributors' trading margins. The resulting costs in basic prices are then allocated to the 75 economic sectors for which the factors are provided and, as a last step, multiplied with the factor of the matching sector. The result is the sector-average carbon footprint of the production of products bought by the entity.
The accuracy of the analysis can be enhanced by using more up-to-date factors and a higher resolution of economic sectors, see below.

How were the supply chain factors calculated?
At CenSA, we employ environmentally extended input-output analysis for these calculations, using official data from the ONS National (economic) Accounts and ONS Environmental Accounts. The supply chain factors supplied to Defra are based on a model of the UK economy using own updates of published input-output tables. For more details on the methodology contact CenSA at infocensa.org.uk.

Are more up-to-date factors available?
We constantly update the supply chain emission factors for the UK using the most recent national economic and environmental accounts data as well as sophisticated, state-of-the-art matrix balancing techniques. We have produced a time series of emission factors from 2004 to 2007 and have estimated those for 2008. Write to CenSA at infocensa.org.uk for more information on factor updates.

Are factors for more economic sectors available?
The factors supplied to Defra have been aggregated to 75 sectors. Our calculations, however, are performed at a much finer level of granularity. On average, we work at a SIC 4-digit level which allows us to distinguish over 500 different product groups. We are able to calculate supply chain emission factors for any of these sectors on demand, depending on the requirements of the client. For more information please contact us at infocensa.org.uk.

Do the factors take into account imports to the UK?
Yes. Imports to intermediate and final demand to the UK from the rest of the world are considered in our model, using world-average GHG emission intensity factors for foreign production.

Is a supply chain / scope 3 calculation tool available?
Yes. CenSA's tool TBL2 incorporates our input-output calculation engine, automatically converts expenditure data from actual (purchaser's) prices to basic prices and calculates complete supply chain carbon footprints at the touch of a button. The tool features sector benchmarking, production layer decomposition, supply chain analysis, and a wealth of graphs and tables for effective results presentation. Click here for more details.

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