Experimenting growing media through local bio-resources valorisation: A design-oriented approach for living walls

In the context of densely populated urban areas, vertical greenery systems are gaining momentum for their role in reintroducing nature and enhancing buildings sustainability. Despite this trend, the absence of a standardised methodology for designing sustainable vertical greenery systems and guidelines for selecting appropriate growing media for this technology are two crucial gaps in academic research. This study addresses this by testing six alternative growing media derived from local bio-resources (dried M. spicatum, hazelnut shells, coffee grounds, hemp stalks, grinded cork, and raw sheep wool) and comparing them with a standard growing medium. The experiment was conducted over 120 days, monitoring the health and growth of three plant species - C. comosum, S. wallisii, and M. spicata. Innovative tools, such as a multi-criteria matrix and the Mean Leaf Growth Index, were introduced to assess sustainability and plant development. The findings highlight promising outcomes for hazelnut shells-based, hemp stalks-based, and grinded cork-based growing media, showcasing their lightweight and stable attributes compared to standard growing medium and assuring good plants health and growth. In contrast, raw sheep wool-based, M. spicatum-based, and coffee grounds-based growing media present challenges in plant health and growth, despite interesting attributes concerning lightweight and low water demand. This research contributes to shaping a design-by-components strategy for more sustainable vertical greenery systems, emphasizing the crucial role of circular bio-resources in nature-based technological innovations.