Why Should We Be Concerned with the Use of Spent Coffee Grounds as an Organic Amendment of Soils? A Narrative Review Pérez Burillo, Sergio Cervera Mata, Ana Gloria Fernández Arteaga, Alejandro Pastoriza de la Cueva, Silvia Rufián Henares, José Ángel Delgado Calvo-Flores, Gabriel Residue Coffee Re-utilization Organic amendment Biofortification Soil quality Spent coffee grounds (SCG) are produced in massive amounts throughout the world as a bio-residue from coffee brewing. However, SCG are rich in carbohydrates, proteins, lipids, bioactive compounds and melanoidins, which are macromolecules with chelating properties. Additionally, SCG have showed potential applications in several fields such as biotechnology (bioethanol, volatile aromatic compounds, carotenoids, fungi and enzymes), energy production (combustion, pyrolysis, torrefaction, gasification, hydrothermal carbonization) and environmental sciences (composting). This review will focus on the last of these applications. SCG improve soil quality by increasing their chemical, physicochemical, physical properties and biological fertility. However, SCG inhibit plant growth at very low concentrations (1%) due to i. the stimulation of microbial growth and consequent competition for soil nitrogen between soil microorganisms and plant roots; ii. the presence of phytotoxic compounds in SCG, such as polyphenols. The SCG transformations that have proven to eliminate these compounds are vermicomposting and pyrolysis at 400 degrees C. However, it has been pointed out by some studies that these compounds are responsible for the chelating properties of SCG, which makes their elimination not recommended. The use of SCG as biochelates has also been studied, generating a residue-micronutrient mixture for the biofortification of edible plants. 2022-12-01T13:04:54Z 2022-12-01T13:04:54Z 2022-11-07 info:eu-repo/semantics/article Pérez-Burillo, S... [et al.]. Why Should We Be Concerned with the Use of Spent Coffee Grounds as an Organic Amendment of Soils? A Narrative Review. Agronomy 2022, 12, 2771. [https://doi.org/10.3390/agronomy12112771] https://hdl.handle.net/10481/78230 10.3390/agronomy12112771 eng http://creativecommons.org/licenses/by/4.0/ info:eu-repo/semantics/openAccess Atribución 4.0 Internacional MDPI