Sustainable Valorization of Spent Coffee Grounds: A Green Chemistry Approach to Soil Amendment and Environmental Monitoring

Nowadays, soil is deteriorating at an alarming rate, endangering both land fertility and productivity and thus the world’s food supply. Using bulk available spent coffee ground (SCG) solid wastes to enrich and amend the deteriorating soil might be revolutionary because it would assist with its correct disposal and lessen the problems related to environmental contamination and human health. The blend of traditional practices and modern technologies can manage SCG’s waste economically, efficiently, and sustainably. The current review article focuses on the potential uses of wasted coffee grounds to improve soil fertility, water-holding capacity, residue management, seed germination, crop growth, and yields. The ability of SCG to amend soil depends upon the nature of SCG (fresh, compost, vermicompost, biochar, etc.), mode of application (extract, mixing, and top dressing), and application rate. The traditional practice of composting using microbes and earthworms to convert phytotoxic SCG into non-phytotoxic compost to enhance crop productivity and soil fertility is quite impressive and has been applied extensively. However, other modern technologies, like SCG-derived biochar, hydrochar, alkaline-treated SCG, SCG-derived nano fulvic-like acid fertilizers, and NPK-organic fertilizers, could be an excellent choice to replace the existing ones. This paper details the recent advancements and effects of various fertilizers on the physicochemical characteristics of soil, compost nutrient composition, plant growth, nutrient uptake by plants, and soil’s ability to store water.