Construction of green roofs via using the substrates made from humus and green coconut fiber or sugarcane bagasse

Abstract

The present paper reports the development of nutritious substrates through the use of renewable materials via vermicomposting. Vermicomposting was carried out using stacked bin composter (14.5 cm high, 78 cm wide and 30 cm long) filled with sawdust/soil mixture, fresh wastes, Eisenia fetida and dry wastes; this led to the generation of humus with chemical composition suitable for use as nutritional component (41.9% moisture; pH 7.3; 31.2% organic matter; 17.5 and 3.2% of fulvic and humic acid, respectively; NPK ratio ~1:1:1). Six different substrates were constructed using the humus generated from vermicomposting and sugarcane bagasse or green coconut fiber. The physical stability and nutritional capacity of these substrates, as well as their application feasibility as substrates for green roofs were evaluated using green roof prototypes. The green roof prototypes were exposed to natural environment with an inclination angle of 45°. The physico-chemical analysis conducted showed that the substrates exhibited suitable field capacity (17–37%), good nutritional properties (0.09–0.46 gkg−1 nitrogen; 92.9–494.6 mgdm−3 phosphorus and 7.0–37.0 mmolcdm−3 potassium) and pH (5.4–7.2) that are ideal for plant nutrition. Comparing the substrates produced from green coconut fiber with those from sugarcane bagasse, it was found that some of those produced from sugarcane bagasse had nitrogen content closer to the range reported as ideal. The density (0.79–1.6 gcm−3) and physical stability of the substrates make them suitable for application as substrates in green roofs, but those from green coconut fiber have relatively lower field capacity, being considered the most suitable for this application.