Living walls: Upscaling their performance as green infrastructure

Abstract

Living wall systems (LWSs) can provide biophilic value and ecosystem services as part of the quest for sustainable development. 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. The researcher monitored fresh and dry biomass yields with a calibrated laboratory balance as the primary performance indicator.  Plant stress, the secondary performance indicator, was measured by chlorophyll fluorescence analysis. Experimental data were  statistically analysed. The findings lay the groundwork for improving LWSs as GI, which can contribute to more sustainable cities.  This is achieved by defining LWSs’ technical characteristics to enhance their performance as GI. 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.

As deel van die strewe na volhoubare ontwikkeling, kan lewende muurstelsels biofiliese waarde en ekosisteemdienste verskaf. Ten spyte  van hul voordele en potensiaal om globale uitdagings krisisse aan te spreek, beperk hul ekonomiese haalbaarheid, veerkragtigheid,  instandhouding en volhoubaarheid hul toepassing en gebruik. Hierdie artikel gee ’n oorsig van ’n pragmatiese studie wat die faktore wat  lewende mure se prestasie as groen infrastruktuur (GI) belemmer, evalueer het, en die werkverrigting van buitemuurse modulêre  lewende mure as GI ontleed het. Die doel is om ’n stel kriteria te ontwikkel om die mees geskikte LWS vir groen infrastruktuur te bepaal.  Datavaslegging het ’n gemengde metode-metodologie behels. Plaaslike kundiges het deur middel van vraelyste insig gegee in plaaslike  lewende mure-tipologieë. Die ses maande-lange eksperimentele studie het twee geselekteerde LWSs van 4m2 elk in omvang op die Universiteit van Pretoria se Future Africa-kampus in Pretoria, in Suid-Afrika se Gautengprovinsie, behels. Veranderlikes het minimum en  maksimum daaglikse temperature, relatiewe humiditeit, neerslag, grondtemperatuur, waterinhoud en elektriese geleidingsvermoë,  blaarbiomassa-opbrengs en plantstres ingesluit. Die navorser het vars en droë biomassa-opbrengste gemonitor met ’n gekalibreerde  laboratorium skaal as die primêre prestasie-aanwyser. Plantstres, die sekondêre prestasie-aanwyser, is deur chlorofilfluoressensie- analise gemeet. Data is statisties ontleed. Die bevindinge lê die grondslag vir die verbetering van lewende mure as GI wat kan bydra tot  meer volhoubare stede. Dit word bereik deur tegniese kenmerke vir lewende mure te definieer om hul werkverrigting as GI te verbeter.  Die resultate bevoordeel plaaslik vervaardigde, lae-tegnologie, buitemuurse modulêre lewende mure met beperkte, robuuste, liggewig, herwonne komponente wat ongekompliseerde samestelling behels. Stelsels moet laetegnologie besproeiing behels. Die lewende muur- posisie moet die plantgewasse se ligvereistes en besoedeling in ag neem. Potte moet beperkte sonblootstelling kry, en ’n grondvolume  van 3 liters en ’n minimum diepte van 200mm hê.