“[A]ny legitimate pathway to net‐zero GHG emissions must include significant changes to the ways societies manufacture and utilize materials. The 19 papers in this special issue… highlight the many ways in which the IE [industrial ecology] community, with its rigorous system‐oriented tools and unparalleled materials cycle expertise, can take center stage in better quantifying, communicating, and realizing the benefits of ME [material efficiency] strategies in climate change mitigation efforts.”

The production of materials accounts for nearly one quarter of global greenhouse gas (GHG) emissions (IRP, 2020). Therefore, any legitimate pathway to net‐zero GHG emissions must include significant changes to the ways societies manufacture and utilize materials. Because decarbonizing material production processes may take decades (IEA, 2020), mitigation analysts and policy makers are increasingly considering material efficiency (ME) as a potentially powerful, if yet largely untapped, climate solution. The urgency of ME solutions is also increasing, given that the remaining 1.5C carbon budget is dwindling and that rapid action is needed to avoid “locking in” inefficient materials uses (e.g., in the built environment) for decades to come (IPCC, 2018; IEA, 2019).

Material efficiency refers to meeting human needs through minimal material production and processing (Allwood et al., 2011). It is often epitomized by such strategies as product lightweighting, lifetime extension, dematerialization, recycling, reuse, more intensive use, and remanufacturing. As such, ME strategies are often highly synergistic with circular economy principles. However, they may also be distinguished by their overarching aim to reduce the total societal throughput of materials by minimizing the demand for materials in the first place. Material efficiency is seen not as a goal, but as a means to specific ends; in the case of this special issue, the ends are reductions of GHG emissions.

Recent analyses suggest that widespread deployment of ME strategies may offer a substantial new mitigation wedge. Furthermore, this new wedge may even relieve pressure on other decarbonization strategies, such as renewable capacity additions and negative emission technology deployments. For example, the International Energy Agency finds that ME strategies can contribute around one third of the needed reductions in GHG emissions related to global cement and steel use (IEA, 2020), while the International Resource Panel finds that ME strategies could reduce emissions from the construction, operation and dismantling of homes by 35–40% in the G7 and up to 50–70% in China and India (IRP, 2020).

This heightened focus on ME presents the industrial ecology (IE) community with important new opportunities for contributing to global decarbonization agendas. Since the early days of the IE field, modeling and assessing the evolution and implications of materials systems have been among its main research focuses. The IE field has also been at the forefront of developing, refining, and applying core methodologies such as material flow analysis (MFA) for studying material stocks and flows, life cycle assessment (LCA) for quantifying emissions at each stage of the materials cycle, and input–output (IO) approaches for better understanding material demand drivers, systems relationships, and trade flows. Systems‐oriented tools like these can help robustly identify opportunities for more efficient materials use across the entire materials cycle, while also ensuring that ME strategies lead to net mitigation benefits.

While the “big picture” potential and importance of ME are now well recognized (Allwood et al., 2011; Material Economics, 2018; IEA, 2019; IRP, 2020), there are still considerable knowledge gaps to overcome when it comes to operationalizing needed changes to the myriad end uses of materials. Addressing these knowledge gaps is where the IE community's unique expertise and systems‐oriented tools can be brought to bear. However, doing so will also require strengthening the IE community's existing bridges and relevance to other stakeholder communities, including mitigation modelers, policy makers, materials and product manufacturers, engineers and designers, and consumers.

These are the motivations for a special issue on material efficiency for climate change mitigation in the Journal of Industrial Ecology, and which make such a special issue particularly timely. The initial call for papers was deliberately broad, recognizing the wide range of methods employed in the IE field and the diversity of knowledge gaps faced by different stakeholders that can be informed by IE methods. The composition of the special issue reflects this breadth and diversity. It includes fundamental methodological contributions, applied decision tools, mitigation potentials analyses for key energy‐intensive materials and products, and scenario analyses meant to inform different stakeholders, particularly policy makers.