1. Introduction

The UK’s material footprint, or raw material consumption, captures the amount of domestic and foreign extraction of materials needed to produce the products used by households, governments and charities in the UK in one year. Such information can be used to examine which products have the largest impact on material extraction.

Estimates of material footprint are provided as part of the UK’s Environmental Accounts. These are “satellite accounts” to the main UK National Accounts and are compiled in accordance with the United Nations (UN) System of Environmental Economic Accounting (SEEA), which closely follows the UN System of National Accounts 2008: SNA 2008. This means they are comparable with other economic indicators such as gross domestic product (GDP).

Estimates of material footprint are used in two (8.4.1 and 12.2.1) of the United Nations Sustainable Development Goals and as a strategic indicator in the Department for Environment, Food and Rural Affairs (Defra) strategy for England “Our waste, our resources”.

This article presents updated estimates for material footprint and discusses some of the methodological issues surrounding its measurement.

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2. Background

In developing estimates of material footprint, the Office for National Statistics (ONS) initially produces material flow accounts (MFA), which look at how materials (such as biomass, metal ores, non-metallic minerals, fossil energy materials and carriers) flow through the economy. This includes estimating levels of material extraction and levels of imports and exports. From this it is possible to calculate the UK’s domestic material consumption (DMC):

DMC = Domestic Extraction + Imports – Exports

One shortcoming of material flow accounts is that the trade flows, that is, the imports and exports, are measured in physical quantities of the good traded and do not consider the raw material that was needed to produce the traded product. For example, if a metal ore is extracted domestically, the total amount of the ore extracted is captured, whereas when metal derived from an ore is imported, only the imported mass of the traded metal (product weight) itself is captured.

To provide a better estimate of how much material is being consumed, measures of raw material equivalent (RME) can be estimated, which include the raw material used to produce a traded product.

By estimating the RME of imports and exports, it is possible to calculate material footprint, often referred to as raw material consumption (RMC).

In 2016, the ONS published the article How much material is the UK consuming?, which included an estimate of material footprint based on the formula:

Material footprint = Domestic Extraction + Imports (RME) – Exports (RME)

The RME of imports and exports was derived using a tool provided by Eurostat.

In 2017, the Department for Environment, Food and Rural Affairs (Defra) consulted extensively with the University of Leeds about developing further environmentally relevant metrics for material use and resource efficiency, particularly in carbon terms. In doing this, the University of Leeds voluntarily reviewed methods to produce estimates of material footprint.

The University of Leeds evaluated several different methods available to the UK and decided it would be best to develop an alternative.

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3. Methods of estimating material footprint

The choice of method used to calculate material footprint has an impact on the final estimates. Section 4.9 of the UN System of Environmental Economic Accounting (SEEA) handbook (PDF, 2.96MB) discusses the options available to countries for reporting this measure but, while it expresses a preference for the approach using “an extended global multi-regional input-output model”, it accepts that “these databases have complex underlying methodologies and national statistical authorities cannot easily use or adapt them for their specific needs”. A measure of material footprint is also an indicator within two of the UN Sustainable Development Goals (8.4.1 and 12.2.1).

This article discusses two approaches where data have been produced for the UK.

Eurostat method

To estimate the material footprint of the EU, Eurostat use an environmentally extended input-output table (IOT) approach for calculating raw material equivalent (RME) of imports and exports. The methodology is based on an integration of data from IOTs, domestic extraction from MFA and life-cycle-inventory data (that is, flows of final and intermediate goods and services defined according to industry or product, supplemented with information on use of raw materials, energy and emissions).

To aid EU countries in developing these estimates, Eurostat has provided a “Country RME tool”. This uses a coefficient approach, where the estimates of RME imports and exports are based on EU-level coefficients for each product. The 2015 version of the model, which assumed that all countries had the same level of production technology, was used to calculate the estimates published by the Office for National Statistics (ONS) in 2016.

Eurostat have since provided an updated version of the tool, where adjusted coefficients allow for country specific differences in production technology. Estimates from this updated model are presented in the Section 5: Results.

University of Leeds method

The University of Leeds has taken a different approach to calculating the UK’s material footprint. They have developed a multi-regional input-output (MRIO) approach, using a specifically derived UK MRIO database to underpin calculations.

Rather than calculating imports and exports in their raw material equivalent form, the MRIO approach takes estimates of domestic extraction by world region and reallocates them to measures of UK final demand. The database is constructed using supply and use tables from the ONS.

Imports to intermediate demand are further disaggregated to show which world regions and sectors are involved in UK intermediate demand. Similarly, exports are disaggregated to show which sectors in which world regions are using UK exports for their own intermediate or final demands. This allows for re-imports (where a semi-finished product is exported from the source country, processed abroad and then re-imported), to be accurately accounted for. Information on the origin and destination of trade flows is taken from the EXIOBASE MRIO database.

More details on the methodology used by the University of Leeds are available. Their latest available estimates were published by Defra (PDF, 1.29 MB) and are also presented in Section 5: Results.

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4. Quality aspects of each method

There are both strengths and weaknesses associated with each of the methods described in Section 3: Methods of estimating material footprint. A high-level summary is given in Table 1.

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5. Results

Figure 1 shows both estimates of material footprint for the UK for 2008 to 2016.

Primarily, given the exclusion of re-imports and exports from the Eurostat model, the University of Leeds estimates show a consistently higher level. Estimates of material footprint by category of material (biomass, metal ores, non-metallic minerals, fossil energy materials and carriers) are presented in Section 8: Annex.

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6. Conclusion

Work on developing estimates of material footprint has been carried out on a non-contractual and collaborative basis to date. The University of Leeds calculate estimates of carbon footprint under contract to the Department of Environment, Food and Rural Affairs (Defra). In future, it is likely that the UK government will require both footprints to be updated annually at both a UK and country level. Both metrics form the basis of commitments in the recently published Resources and Waste strategy for England and are used to help the UK fulfil its commitment to reporting Sustainable Development Goals (SDGs).

The Office for National Statistics (ONS) will continue to work with interested parties to help ensure publication of regular estimates of material footprint and explain to users any differences in methodology used in publicly available estimates of material footprint. The ONS will feed into and monitor international decisions as to which method is used for estimating material footprint in the UN SDGs.

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8. Annex

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Contact details for this Methodology

Hazel Clarke or David Ainslie
Telephone: +44 (0)1633 455633