Summary: In light of the environmental consequences of linear production and consumption processes, the circular economy (CE) is gaining momentum as a concept and practice, promoting closed material cycles by focusing on multiple strategies from material recycling to product reuse, as well as rethinking production and consumption chains toward increased resource efficiency. Yet, by considering mainly cost‐effective opportunities within the realm of economic competitiveness, it stops short of grappling with the institutional and social predispositions necessary for societal transitions to a CE. The distinction of noncompetitive and not‐for‐profit activities remains to be addressed, along with other societal questions relating to labor conditions, wealth distribution, and governance systems. In this article, we recall some underlying biophysical aspects to explain the limits to current CE approaches. We examine the CE from a biophysical and social perspective to show that the concept lacks the social and institutional dimensions to address the current material and energy throughput in the economy. We show that reconsidering labor is essential to tackling the large share of dissipated material and energy flows that cannot be recovered economically. Institutional conditions have an essential role to play in setting the rules that differentiate profitable from nonprofitable activities. In this context, the social and solidarity economy, with its focus on equity with respect to labor and governance, provides an instructive and practical example that defies the constraints related to current institutional conditions and economic efficiency. We show how insights from the principles of the social and solidarity economy can contribute to the development of a CE by further defining who bears the costs of economic activities.

The transition from a fossil fuel base to a renewable energy system relies on materials and, in particular, metals to manufacture and maintain energy conversion technologies. Supply constraints shift from fossil fuels to mineral resources. We assess the availability of metal reserves and resources to build an energy system based exclusively on renewable energy technologies. A mass balance of 29 metals embodied in renewable energy technologies is compiled in order to satisfy global energy demand, based on five authoritative energy scenarios for 2050. We expand upon these scenarios by modeling the storage capacity needed to support high shares of intermittent renewables (wind and solar). The metal requirements are then compared with the current demand and proven reserves and ultimate mineable resources. This allows us to distinguish between constraints related to renewable energy sources from those linked to technology mixes. The results show that proven reserves and, in specific cases, resources of several metals are insufficient to build a renewable energy system at the predicted level of global energy demand by 2050. The comparison between reserves and resources shows that scarcity relates sometimes more to techno economic supply than to raw material availability. Our results also highlight the importance of substitution among technologies and metals as well as the limited impact of recycling on the depletion of scarce metals.

Decision makers increasingly recognise the importance of lifestyle changes in reaching low emission targets. How the mitigation potential of changes in mobility, dietary, housing or consumption behaviour compare to those of ambitious technological changes in terms of decarbonisation remains a key question. To evaluate the interplay of behaviour and technological changes, we make use of the European Calculator model and show that changes in behaviour may contribute more than 20% of the overall greenhouse gas (GHG) emission reductions required for net-zero by 2050. Behaviour and technology-oriented scenarios are tested individually and in combination for the EU plus the UK and Switzerland. The impacts of behavioural change vary across sectors, with significant GHG emission reduction potential and broader benefits. Changes in travel behaviour limit the rising demand for electricity, natural resources and infrastructure costs from the electrification of passenger transport. Adopting a healthy diet reduces emissions substantially compared to intensifying agricultural practices, while at the same time making cropland available for conservation or bioenergy crops. The trade-offs between energy and food may be substantially alleviated when deploying technological and behavioural changes simultaneously. The results suggest that without behavioural change, the dependency of Europe on carbon removal technologies for its net-zero ambitions increases. Structural changes will be necessary to achieve full decarbonisation by 2050, yet changes in lifestyles are crucial, contributing to achieving climate targets sooner.