Prospects for the integration of lignin materials into the circular economy

Lignin is a remarkable natural polyphenol that provides trees with physical and (bio-)chemical resistance, as well as the ability to reach considerable heights. Lignin is also intrinsically circular with slow biodegradability, thereby serving as a carbon source for soils. There is a growing interest in using industrial lignin as an environmentally and economically beneficial material. However, most of the industrially produced lignin is still used as a cost-efficient energy source by the forestry sector. To efficiently redirect the use towards material applications and to avoid the end-of-life problems connected to traditional plastics, there is an imminent need and opportunity to include circularity as an important design parameter. In this review, we critically assess opportunities and obstacles for lignin as a component in circular materials, as guided by life cycle assessment and benchmarking to best practices in materials science and engineering, e.g., circularity “by design”. We cover and reflect on recent and emerging advances in nanotechnology and materials science that showcase how lignin can contribute to carbon fixation as a viable alternative to its combustion in the pulping processes. We argue that, with adequate considerations, lignin has the potential to enable the development of new circular biobased materials that do not cause accumulation of environmentally persistent waste, and are equipped with attractive functionalities and performance for the benefit of a sustainable society.