Material stocks in a circular economy

Why do material stocks matter?

Material stocks are the materials accumulated in economies that make up all built structures and long-lasting products (with life spans of more than a year) (Figure 1). They include buildings, roads, cars, as well as products such as mobile phones.

Stocks form the long-lasting biophysical basis of societies and are an important part of everyday life. They are essential for quality of life. For example, they are necessary for providing energy, water, healthcare in hospitals and mobility. As such, minimum levels of stocks are required to ensure minimum life-quality standards. Historically, stocks have been closely linked to the growth of economies.

Action to build up material stocks can be taken by private individuals, enterprises or the state: a private person can decide to build a house, a company can invest in machinery and the state can build hospitals. The socio-economic conditions, levels of prosperity and the level of inequalities in a society determine:

• who builds stocks;
• how large these are;
• who is responsible for their operation and maintenance;
• how evenly they are distributed across all parts of society.

Figure 1. Accumulation process for material stocks

Policymaking and academic research, as well as data collection, often focus on the physical in- and out-flows of an economy, meaning that the long-lasting biophysical basis of societies is overlooked. However, material stocks are arguably the most important driver of resource consumption.

Over the past century, the global expansion of material stocks and their maintenance has driven the increase in resource consumption. Today 55% of global resource use can be attributed to material stocks (up from 20% in 1900) (Krausmann et al., 2018). The remaining 45% of resource use ends up in short-lived products like food or fossil fuels.

Extracting and processing natural resources is proven to cause significant environmental harm (UNEP, 2024). Since building, maintaining and operating stocks involves such a large share of resource consumption, using material stocks is also linked to significant environmental pressures.

Europe has an ambition to establish a climate-neutral, resource-efficient and competitive economy, by establishing a circular economy that minimises the use of primary raw materials while increasing the economy’s resilience and security. Such an economy is underpinned by circular product design, resource-efficient production, extension of product life times and high-quality-oriented recycling (EEA, 2024a). Progress towards this kind of sustainable circular economy would help reduce overall primary resource demand, including widespread European dependencies on resource imports from abroad.

Although a lot of the resources do not become part of stocks, like fossil fuels or food, stocks for many raw materials used in Europe, such as metals and minerals, are expanding and need maintaining. As such, existing stocks, which have already been accumulated in the EU economy, could prove to be a valuable source of secondary materials.

Using these stocks could help decrease the economy’s dependence on primary materials, which are often imported from abroad, including most critical raw materials (CRMs). However, this could be challenging as existing stocks were constructed before the concept of circular economy was even conceived. Consequently, circularity principles are often not embedded in the way they are designed, making it complex to make use of them.

This briefing describes and analyses material stocks in Europe to better understand their potential for circularity and sustainability, and how to overcome the barriers to using them.

Status and trends

Growing material stocks

In 2022, material stocks in the EU totalled 154 billion tonnes. This equates to 11% of global material stocks. At the same time, the EU accounts for about 5.5% of the global population and 14.7% of global gross domestic product (GDP).

Also in 2022, 41% of total material consumption in the EU was used to expand and maintain material stocks. This percentage is lower than the global average due to the fact that there are already high existing stocks levels in Europe. This figure includes material consumption for:

• new products, buildings and infrastructure;
• replacing items that are discarded (e.g. mobile phones);
• maintaining existing stocks (e.g. the renovation of buildings).

Material stocks per capita are relatively high in the EU — about 344 tonnes per person — including around:

• 124 tonnes of buildings;
• 1.4 tonnes of machinery and equipment;
• 1 tonne of motor vehicles;
• 259kg of other durable goods;
• 31kg of textiles.

The per capita figures are higher in the EU than in other countries such China or Japan — yet still below the United States (see Box 1).

Material stocks in the EU have been growing since the 1970s and nearly tripled between 1970 and 2022 (from 117 to 344 tonnes per capita) (Figure 2). This growth, which varies across EU countries (see Box 1), was similar to the growth in EU GDP but much higher than the proportional increase in population.

Stock growth per year has slowed down in the last couple of decades. However, the need for materials to maintain and replace stocks has continued to increase (see section on barriers to circularity).

Composition of stocks

Construction materials, especially concrete and aggregates, dominate EU stocks (93%). Iron and steel account for 4%, wood for 2% and the remaining 1% is made up of all other materials such as glass, plastics, non-ferrous metals and non-metallic minerals. Some of these are CRMs.

While no significant changes have been observed in the proportional composition of material stocks over the 1970-2022 period, plastics, non-ferrous metals (mostly copper and aluminium) and non-metallic minerals (mainly bulk flows such as concrete, aggregates, asphalt, bricks) have increased very significantly since 1970, from doubling to more than tripling (Figure 2).

Figure 2. Material stocks per capita by material between 1970 and 2022

What material stocks are used for

Just four groups of applications, concentrated in settlement areas and transport corridors, account for 98.5% of material stocks (152 gigatonnes (Gt)):

• roads;
• other types of civil engineering (such as railways, bridges, tunnels, water supply pipes, harbours, dams or power plants);
• residential buildings;
• non-residential buildings.

The remaining 1.5% (2.3Gt) are found in products such as office machinery, industrial machines, cars and trains, books and magazines, as well as small amounts of electronics and household appliances, clothes and household textiles (Figure 3).

Over the entire 1970-2022 period, the biggest increases in material stocks were related to infrastructure and buildings. They included large gross additions to stockpiles and for the maintenance or replacement of existing stocks to keep them functioning.

The production of certain stocks involves significant environmental implications. Since 1970, production in these areas has grown significantly in relative terms. For example, stocks of textiles per capita have increased more than 4 times, and electrical equipment, computers and other consumer products not otherwise classified have more than doubled. Vehicles have increased close to 50% and furniture close to 75%.

Different kinds of products use different kinds of materials. Non-metallic minerals are mainly used as construction materials in buildings, roads and other infrastructure. Metals, wood and plastics are used across a broader variety of products such as machinery, vehicles, furniture or other consumer products.

Most stocks are low-value materials like sand, gravel and stones. Inversely, only 5% of total stocks are high-price materials used for high-value assets such as vehicles, machinery or appliances.

The bulk materials that make up most stocks do not always have the largest environmental impacts (EEA, 2023a). CRMs are a good example of this. They have high strategic importance for the EU and while they are used in rather small amounts, they are generally characterised by higher direct environmental impacts.

Figure 3. Material stocks by end-use application between 1970 and 2022

Barriers to circularity

The magnitude and continuous growth of stocks

The enormous quantity of materials we use every year to build up, operate and maintain stocks within the EU economy (6.2 tonnes per person per year) is the main barrier to the deployment of a circular economy that minimises resource use in Europe. As long as stocks are growing, even a theoretical 100% recycling level could not provide the materials to maintain and expand stocks.

Consequently, the continuous growth of stocks has been identified as a major barrier to closing material loops globally. On the other hand, the largest share of all waste generated in the EU originates from discarded stocks. Only systematic knowledge about the materials constituting stocks, their life spans and their geographic location can inform a high level of material recovery and close the loop.

The example of batteries — with their accelerating use in Europe, their complex chemistry and high dispersity — illustrates this barrier to higher circularity (see Box 2).

Lock-ins to high material-consuming stocks

Stocks not only hinder a circular economy, they also lead to future lock-ins in terms of material demand: the ubiquity of material stocks results in a high material demand to operate and maintain those stocks. Examples include the energy use to operate a house with all its appliances or materials to renovate or replace old infrastructure.

In the EU, more than half (52%) of material inputs to stocks are used for maintenance and replacement — slightly more than the amount of material required to expand stocks — and these amounts have been constantly increasing. This situation contrasts with 1970, when most material inputs (92%) were dedicated to the initial build-up of stocks.

This comparison illustrates that while stock accumulation is predominant in early industrialisation phases, maintenance and replacement become the primary resource demands in mature economies. This creates a lock-in effect at relatively high levels of material consumption. As such, growing material stocks equate to an overall increase in material consumption and its related environmental impacts.

Constant demand for new material stocks

Data show that the number of batteries and cars used by an average EU citizen has increased since 2011; additionally, the average EU citizen now lives in a household with more square metres (m²) per person compared to 2011 (Figure 6). Two of the factors leading to more floor space per person have been the expansion of low-density suburban areas and changing demographics in the EU (EEA, 2024b).

Taking the example of energy use in housing, consumption per material stock unit has decreased due to efficiency gains; however, the gains have not been sufficient to compensate for the increase in stock volume, which has multiplied by a factor of more than seven. Moreover, the green energy transition is creating demand for additional energy infrastructure and the replacement of old (fossil-based) stocks.

One of the reasons for the continuous growth of stocks is the constant increase in consumption. The predominant lifestyle in the EU, especially for those with a high income, constantly creates demand for more products (a house, a car, the related infrastructure or electronics). This is driving stock increases.

In 2008, the average useful floor area per person in the EU was 35.9m²/person. In 2020, it had increased to 38.44m²/person. This represents a more than 7% increase in 12 years.

The average number of cars per household increased from 1.21 to 1.27 cars/household between 2016 and 2020 alone, though this stabilised over the following 2 years. In addition, cars are getting bigger (a change that is again driven by wealthier individuals): in 2023, the average mass of a new passenger car was 1,545kg representing a 20.7% increase compared to the 2001 figure.

Figure 6. Passenger cars, floor area and batteries placed on the market per person in the EU

Geographical dispersion of material stocks

Overall, 98.5% of existing stocks are in the form of buildings or infrastructure like roads, dams, bridges and railroads. When these reach the end of their service life, they could potentially become a source of secondary raw materials. However, the geographical dispersion of such discarded assets (e.g. in abandoned villages in rural areas) makes it difficult to use them as secondary raw materials in other locations where material demand is high (e.g. in cities). This issue creates stranded assets.

Moreover, lock-ins, mainly for economic reasons, might delay the circular and green transition, as it is hard to move away from certain unsustainable patterns with the current infrastructure (e.g. power plants, extensive road networks).

Economic considerations

When discussing the potential for material stocks to replace primary raw materials as an alternative feedstock, the economic viability of sourcing such secondary raw materials is prominent. Most of the waste generated from material stocks — in terms of weight — is non-metallic minerals, for instance, from demolition activities.

Although recycling is the best treatment option in environmental terms for most demolition materials, it is also the most expensive (Caro et al., 2024). This is despite economic policy interventions like taxes and levies, which attempt to reflect the negative externalities of incineration and landfilling.

On the other hand, the mechanisms that connect recycling with manufacturing industries — namely secondary raw material markets — are, in many cases, not functioning well (EEA, 2023b). Technological, regulatory and economic interventions are needed to make secondary materials from material stocks attractive and competitive.

Increasing the circularity of material stocks

Europe has spent many decades building up material stocks, which amount cumulatively to 154 billion tonnes of mainly technical materials. The analysis presented in this briefing shows that, although the composition of stocks doesn’t match precisely the composition of material inputs needed by the EU economy every year (biomass and fossil materials are not accumulated in stocks but are largely used to feed humans and animals and to operate stocks), stocks reaching the end of their life can offer a wealth of secondary raw materials.

Even for materials less prevalent in stocks, like CRMs, the opportunities for using stocks as secondary sources are not negligible: for example, the concentration of gold in discarded electronics could be 100 times higher than the concentration in gold ore (Fritz and Schmidt, 2025).

By supporting targeted development of technology and fixing the economics of secondary raw material markets, the EU can create alternative sources of materials, based on stocks. At the same time it can reduce its dependencies on imports and advance its own security.

Additionally, increasing the circularity of new stocks can make a very significant contribution to the medium- or long-term goal of establishing a circular economy in Europe. Effective circularity strategies for both existing and new material stocks are given below:

• Design for longevity and repairability reduce the demand for new stocks in the longer term, thus reducing demand for raw material consumption. This is particularly relevant for the main stock applications like buildings, infrastructure and machinery. However, due to the long life spans of some stock applications, flexibility needs to be built into the design process. For example, incorporating modular design in building planning allows for future changes in building use (EEA, 2022).
• In order to enable end-of-life recycling of stocks, the main stock applications need to be designed for recycling. This approach involves designing products whose components and materials can easily be separated, that do not lose their properties and purity over time and that are suitable for high-quality recycling. Increasing the use of single fibre types in textile design, for instance, increases the possibility of closed-loop textile recycling.
• When planning large stock applications, such as buildings and infrastructure, long-term demographic projections must be taken into account, in order to encourage the use of existing stranded assets and to avoid creating new ones.
• Intensifying the use of stocks that already exist dampens the demand to build up new stocks. Making more use of Europe’s existing housing stock and making an effort to match housing supply and demand, for example, can reduce the need for additional buildings and contribute to the mitigation of the housing crisis faced by many EU capitals.
• In the context of a long service life for many material stock applications, product passports can mitigate the risk of losing information about material compositions or repair and recycling opportunities. This is especially urgent in the case of products like electronics or batteries made up of complex chemistries for which high-quality recycling is complicated (see Box 2).
• When stocks reach the end of their life, better waste sorting and higher separate collection, as well as a focus on the quality of sorted materials, closes loops in stock applications like buildings, infrastructure and machinery; it also safeguards valuable materials like critical minerals in waste electronics thereby making the EU economy more resilient.
• Due to the large quantities of materials generated as waste from stocks, the EU’s recycling capacity needs to be scaled up and recycling technologies need to focus on recycling quality so that relevant materials such as critical minerals are not lost.
• Economic incentives and regulatory frameworks need to be put in place to improve the economic viability of recycling material stocks so they produce a material feedstock that is directly competitive with primary material supply.

Together, all these strategies can make a difference in the EU’s pursuit of material supply security and industry competitiveness. On the raw material supply side, increasing the longevity of stocks and reducing material needs for operating existing stocks lowers demand for primary raw materials. This in turn alleviates EU dependencies on imports. Targeting specific material stock applications like electronic products or batteries in the aforementioned circular strategies can increase the security of Europe’s CRM supply.

Meanwhile, the high concentration of metals and minerals in existing stocks offers opportunities for developing alternative sources of raw materials through the use of existing or discarded stocks. Making use of these sources allows the EU to safeguard raw materials for its industry in a cost-competitive manner, as long as the secondary raw material markets operate at their full potential.

Recent EU initiatives are moving in the right direction. The Ecodesign for Sustainable Products Regulation focuses on durability, thus promoting the longevity of products, many of which accumulate as stocks. The Critical Raw Materials Act, with its recycled content targets, works as a ‘pull factor’ for developing recycling technologies for stocks with a high concentration of critical minerals.

Moreover, the potential of material stocks to deliver a steady supply of secondary raw materials to the EU internal market supports the objective of the upcoming Circular Economy Act. However, swift and ambitious implementation is needed, which focuses on the elements outlined in this briefing in order to accelerate the transition to a European circular economy.