Brewing sustainability: unveiling the potential of coffee ground as green roof media

Abstract The rapid depletion of the world’s natural resources and the growing concerns about sustainability underscore the importance of environmentally friendly solutions more than ever. One such solution is green roofs, which offer numerous ecological benefits, particularly in urban areas, such as creating natural habitats, enhancing energy efficiency, and improving air quality. Recently, as access to safe food has become more challenging and economic conditions have not been that stable all over the world, the importance of green roofs has been increasing in urban areas where it is difficult to create green surfaces for many reasons, especially profit. In this context, using coffee grounds as a green roof plant growth medium and a waste product holds significant potential for waste management and sustainable agriculture. With the influence of previous researches, coffee grounds are supposed to support plant growth due to their high organic matter content and nutrient values. This study aims to support the environmental benefits and the contribution of this approach to sustainable urbanization by examining the effects of using coffee grounds on green roofs on plant development. This study assessed the growth of Fragaria ananasa and Sedum spurium in growing media comprising 20% and 50% coffee ground. In F. ananassa a reduction of 9.25–13.58% in plant height, 18.71–23.93% in the number of stolons, 1.36–40.34% in chlorophyll content, and 10.49–13.78% in plant diameter was noted in the medium containing 20% coffee ground, while an increase of 39.20-45.81% in the fruit count and 4.79–9.42% in root collar diameter was recorded in the medium devoid of coffee ground. In S. spurium , a 22.76% reduction in plant height, a 13.11% decline in chlorophyll content, a 25.26% decrease in plant diameter, and a 4.40% increase in root collar diameter were recorded in the medium containing 20% coffee ground. A medium including 50% coffee ground resulted in a 42.36% reduction in plant height, a 12.44% reduction in chlorophyll content, a 46.13% reduction in plant diameter, and a 19.10% reduction in root collar diameter. The results indicate that the impact of coffee ground on plant growth varies based on the ratio, necessitating the establishment of suitable application ratios.