Living walls: Upscaling their performance as green infrastructure

Abstract

Living wall systems can provide biophilic value and ecosystem services. Despite their benefits and potential to mitigate global challenges such as cooling, air purification, sound absorption, and human well-being, their economic feasibility, resilience, maintenance, and sustainability impact on their application and use. This article gives an overview of a pragmatic study which synthesised the factors hampering LWSs’ performance as green infrastructure (GI) and analysed the performance of outdoor modular LWSs as GI. The study aims to establish criteria for selecting the most suitable LWSs as green infrastructure. Data capturing involved a mixed-method methodology. Local experts provided insight into local LWS typologies through questionnaires, which were analysed qualitatively. The six-month experimental study involved two selected LWSs of 4m² each in extent on the University of Pretoria’s Future Africa campus in Pretoria, in South Africa’s Gauteng province. Variables included minimum and maximum daily temperatures, relative humidity, precipitation, soil temperature, water content and electrical conductivity, leaf biomass yield, and plant stress. Fresh and dry biomass yields with a calibrated laboratory balance was the primary performance indicator. Plant stress, the secondary performance indicator, was measured by chlorophyll fluorescence analysis. Experimental data were statistically analysed.  The results favour locally produced, low-technology, outdoor modular LWSs with limited, robust, lightweight, recycled components entailing uncomplicated assembly. Systems must involve low-technology irrigation. The LWS position should consider the plant crops’ light requirements and pollution. Pots should receive limited sun exposure and have a soil volume of 3 litres and a minimum depth of 200mm.