• Indicators are useful to support circular economy progress. • Circular economy has different definitions entailing challenges for indicators. • A classification framework to understand what indicators measure is proposed. • Most of the analysed indicators focus on the preservation of materials. • None of the analysed indicators focuses on the preservation of functions.

Every twig and splinter used: Plant-based production of commodity chemicals faces steep competition from fossil resources, which are often cheaper and easier to partition. Sustainable use of renewable resources requires strategies for converting complex and recalcitrant biomolecules into streams of chemicals with extraordinary efficiency. Liao et al. developed a biorefinery concept in which wood is eventually fully converted into useful chemicals: phenol, propylene, pulp amenable to ethanol production, and phenolic oligomers that can be incorporated into ink production (see the Perspective by Zhang). A life-cycle assessment and techno-economic analysis highlight the efficiency of the process and reveal the potential for such biorefinery strategies to contribute to sustainable chemicals markets. Science , this issue p. 1385 ; see also p. 1305

This article summarizes the energy savings and environmental impacts of using traditional and bio-based fiber-reinforced polymer composites in place of conventional metal-based structures in a range of applications. In addition to reviewing technical achievements in improving material properties, we quantify the environmental impacts of the materials over the complete product life cycle, from material production through use and end of life, using life-cycle assessment (LCA).