Assessing the Effect of Spent Coffee Grounds Compost on the Chemical, Physical, and Biological Properties in an Urban Soil

The accumulation of heavy metals poses significant challenges to urban soil. Food waste, particularly spent coffee grounds (SCGs), contributes to landfill overflow and environmental degradation. Composting SCG and incorporating it into urban soils provides a sustainable solution for mitigating these risks by recycling organic waste and minimising waste sent to landfills. This study examines the effects of composting SCGs indoors and outdoors on the chemical, physical, and biological properties of urban soil. In this study, SCGs were composted indoors and outdoors and applied to urban soil at different rates (0, 5, 10, 20, 30, 40, and 100%). A comprehensive analysis was performed to evaluate changes in soil pH, nutrient content, water holding capacity (WHC), organic matter (OM), and soil respiration (CO ₂), as well as examine the impact of composted SCGs on seed germination. The results indicated improvements in urban soil fertility and structure following the application of composted SCGs. The compost demonstrated improvement in plant development, indicating the absence of any phytotoxicity. The compost amendment increased the availability of OM, potassium, and phosphorus in indoor and outdoor composts, promoting healthier soil. WHC and CO ₂ have shown a significant difference between both composts (p <0.05), with indoor compost having lower CO ₂ and higher WHC. These differences were detected because of the different environmental conditions surrounding the compost. Overall, this study emphasises the positive effects of composting SCGs on urban soil quality, indicating its potential as a sustainable solution for waste management and soil restoration initiatives. These findings contribute to promoting sustainable practices and creating a circular economy in line with Newcastle City Council for achieving sustainable development goals and 'zero landfill policy' goals.