Title: Recycling spent coffee ground in sustainable building and construction materials: A review

Abstract

This paper discusses the development of sustainable bio-composite hydraulic mortars intended as novel building and construction materials. Specimens were produced by upcycling spent coffee ground, a major residue of the brewing process, in light of the Circular Economy approach. This bio-waste has been recently found to be harmful for the environment and humans if landfilled, hence finding alternative solutions is extremely important to limit its footprint. In this review, the possibility of reusing spent coffee ground as mortars’ aggregate is discussed. Various typologies of binders and wastes quantities are tested to foresee possible applications in construction. The materials engineering performance was deeply investigated to predict the feasible applications. The major results are that the used coffee waste, along with the binders’ blend, deeply influences the engineering properties of the developed materials. In particular, by improving the waste amount the bulk density and the mechanical performance tend to decrease; nevertheless, the most of the tested mix could find proper uses for masonry applications according to the relevant standards. Moreover, the observed encouraging energy performance makes all the formulations efficacious for energy applications in architecture granting financial saving in the building yearly management for the deep energy efficiency improvement of the building envelope. The high amount of reused bio-waste makes the material highly green and a promising candidate for the Environmental Minimum Criteria (CAM) certification, in light of the recent EU regulations. Sustainability is also boosted by the manufacturing process that completely occurred at ambient conditions (20 °C, 65% RH) by simple operative steps reproduceable in a real construction site. Finally, a promising alternative reuse of spent coffee ground is proposed to the conventional landfill, that has been found to be potentially harmful to the natural environment and humans, making also the developed mortars greener, in light of the Circular Economy approach, and cheaper.