How will a sustainable circular economy look like?

Sustainability, with its environmental, social, and economic dimension, needs to be made tangible and operational for different actors. One such vehicle to deliver sustainability is the vision of a circular economy (CE), a way of production and consumption that maximises the useful service life of material and minimises resource extraction and waste that needs to be discarded to the environment.

How does the circular economy work?

In particular, the CE is defined as an “economy that is restorative and regenerative by design, and which aims to keep products, components and materials at their highest utility and value at all times, distinguishing between technical and biological cycles”, where ‘restorative’ refers to spent resources being fed back into new products and services, and ‘regenerative’ refers to the enabling of living systems to heal and renew the resources that are consumed (BSI, 2017, P10). Value is defined as “financial and/or non-financial gain” (BSI, 2017, P21).

The goal of the CE is to establish a new economic model that aims to decouple economic growth from the consumption of finite resources. It is based on the principles of designing out waste and pollution, keeping products and materials in use for as long as possible, and thus contribute to the regeneration of ecosystems. The circular economy seeks to create a closed-loop system of production and consumption, where resources are used, reused, and regenerated, minimizing the generation of waste and environmental impact.

The CE links to consistency dimension of sustainability, which emphasizes that in a sustainable world, the natural and technical material cycles need operate without substantial negative mutual interference, such as destructive resource extraction and waste disposal.

In practice, the CE deploys a number of strategies to narrow (less material use), slow (longer material use), and close (better recycling) technical material cycles. These strategies include product light-weighting, longevity, and demountability by design, higher yields in fabrication, scrap recovery, and recycling, as well as more efficient use of products.

For example, lifetime extension is a key component of the circular economy. Rather than designing products with short useful lifetimes or even planned obsolescence, where they are intended to have a short lifespan and be replaced frequently, the circular economy encourages designing products for durability and longevity. This includes creating modular and repairable products that can be easily upgraded or fixed, extending their useful life. By extending the lifespan of products, the circular economy reduces the need for new production and conserves resources.

Better recycling is another critical element of the circular economy. It involves designing products and materials with recycling in mind, ensuring that they can be efficiently and effectively recycled at the end of their life. This includes using standardized materials and components that are easy to separate and recycle. Additionally, the circular economy promotes the development of advanced recycling technologies to handle complex materials and products that are difficult to recycle using conventional methods. By improving recycling processes, the circular economy aims to retain the value of materials and reduce the demand for virgin resources.

Why isn’t our economy more circular?

There are several reasons why our current economy is not more circular, and they are illustrated in the figure below (Fig. 3 from Mayer et al. (2019)).

Figure: Material flows through the EU28 economy in 2014. In this Sankey diagram, the width of the arrows is proportional to the size of material flows (dark blue); the numbers show the size of the material flows in Gt/yr and the bars their composition (share of four main material groups in %). Note that numbers may not always sum up to total due to rounding. EU28 = European Union; Gt/yr = gigatons per year. Figure and legend are from Mayer et al. (2018).

There are large material flows that are used for energy conversion, namely fossil fuels and biomass. These are processed only once to extract useful energy and then, the resulting CO2 emissions are released to the atmosphere. Reducing (fossil fuels) and carefully managing (bioenergy) these flows are to crucial consistency strategies for a sustainable future. Using less fossil fuels is the core of the energy transition, and biomass use within planetary boundaries is subject of the so-called bio-economy.

The circular economy relates to material use flows in Fig. 3, and here, we have throughput materials, like paper and packaging materials, which are only used once and then discarded. The largest fraction of material use are stock-building materials, like concrete in buildings, steel in vehicles, or copper in appliances. These materials accumulate in in-use stocks of buildings, infrastructure, vehicles, machinery, and appliances.

We see that in the EU, the accumulation of material in stocks is four times larger than the outflow of materials in discarded products. Stocks are growing, as more houses, roads, and factories are being built. Material demands of growing stocks cannot be met with domestic recycling, because recycling needs a waste material flow from the stock in the first place. Stock growth requires natural resource extraction or import of materials from other economies, and the high level of stock growth in the EU is the main reason for why its economy is not more circular.

A sustainable circular economy manages its in-use stocks so that that unnecessary growth of stocks of materials, whose extraction and processing comes with high climate, social and ecosystem impacts, is avoided (narrowing principle).

The second main reason for high losses of material is the so-called ‘linear economy’, which follows the ‘take-make-dispose’ model and which has been deeply ingrained in our economic systems for many years. This model focuses on maximizing production and consumption, often with low quality and short-lived products and with little consideration for the long-term impacts on resource depletion and environmental degradation. The linear model incentivizes rapid turnover of products and encourages a “throwaway” culture. Profit-driven decision-making with a short time horizon stymies the adoption of circular practices that require a change in business models, policy support (like eco-design standards and change in taxation), and upfront investments in infrastructure for recycling, remanufacturing, and refurbishing.

A sustainable circular economy encourages designing products for durability and longevity. This includes creating modular and repairable products that can be easily upgraded or fixed, extending their useful life. By extending the lifespan of products, the circular economy reduces the need for new production and conserves resources (slowing principle).

Finally, out of the 2.2 Gt of material waste that accrued in the EU in 2014, only one third was recycled, the rest was incinerated or sent to landfills. Incentives for better recycling are crucial for resource savings in a circular economy.

A sustainable circular economy means that products and materials are designed with recycling in mind, and it promotes the development of advanced recycling technologies with high yields (closing principle).


What is the role of science in building a circular economy?

Science plays a crucial role in building a circular economy by providing both the process/technology knowledge and the systems knowledge on the benefits and trade-offs of the different CE strategies.

Science explores and develops new technologies, materials, and processes that enable circular practices. This includes developing advanced recycling techniques, designing eco-friendly materials, and improving resource efficiency in manufacturing. Scientists work on creating new materials with improved properties, durability, and recyclability. This includes developing biodegradable materials, bio-based alternatives, metal alloys that can tolerate impurities from recycling, and exploring the potential of emerging technologies like additive manufacturing (3D printing). Science plays a role in optimizing production and manufacturing processes to reduce waste, energy consumption, and environmental impacts. Science contributes to the development of advanced recycling technologies that can handle complex and mixed materials, such as plastics, electronic waste, or textiles. These technologies involve chemical or mechanical processes to break down materials into their constituent components for reuse or conversion into new products. Scientific research helps refine and scale up these technologies, making recycling more efficient and economically viable.

Next to the material and process-based development, system knowledge for CE is crucial. With system knowledge, we describe the economic, social, and environmental implications of different CE measures, including co-benefits and trade-offs between strategies. For example, recycling rates of metals from electronics can be increased to a point there the energy costs for additional material extraction are so high that the impacts of that energy supply outweigh the impacts of using virgin material instead. CE adoption my require tax reforms and new regulations, which has macroeconomic implications on labour demand and tax revenue.

To understand these systemic implications, interdisciplinary research is needed: Building a circular economy requires collaboration between various scientific disciplines, such as engineering, chemistry, economics, as well as environmental and social sciences. Interdisciplinary research helps assess the environmental, economic, and social impacts of different products and processes in a CE, such as the socio-economic implications of circular practices, understanding consumer behaviour and preferences, designing and assessing new business models, or assessing the effectiveness of policy measures.

Model-based assessments are a core tool to address these issues. Model-based assessments quantify the likely environmental, social, and economic impacts of different policy options, guiding decision-makers in designing appropriate incentives, standards, and regulations. Models are needed to evaluate the effectiveness of policies and identify areas where adjustments or improvements are needed. Models are used to quantify system indicators that cannot directly be measured, such as rebound effects of CE strategies and environmental footprints (LCA) of products.

In CIRCOMOD, we undertake a comprehensive data collection and model-building activity to help generate scientific insights on the effectiveness and system-wide implications of the different CE strategies. CIRCOMOD will equip national, EU, and international policymakers with key policy insights by providing: (i) the first-of-a-kind scientifically rigorous modelling of potentials of CE for environmental, climate, and economic action; and (ii) enriched CE datasets necessary for policy intelligence, monitoring of CE interventions and interactions with GHG emissions and climate. These step-changes will help move the CE from mainly qualitative science to quantitative, robust, data-based, and systems-level impact assessment. It will thereby support improved political decision-making (climate, industry, innovation policy) to safeguard planetary boundaries. These new models will directly influence the European Green Deal’s objectives if utilized by policymakers and inform climate and CE policies globally. As the refinement of nationally defined contributions (NDCs) of the Paris Agreement will become increasingly important in the coming years, CIRCOMOD will provide a much greater understanding of CE contributions.



BSI, 2017. BS 8001:2017. Framework for Implementing the Principles of the Circular Economy in Organizations – Guide. The British Standards Institution, London.

Mayer, A., Haas, W., Wiedenhofer, D., Nuss, P., Blengini, G.A., 2019. Measuring Progress towards a Circular Economy A Monitoring Framework for Economy-wide Material Loop Closing in the EU28. J. Ind. Ecol. 23, 62–76.







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