Evaluation of physical and chemical parameters of substrates and food waste composts for application in green roofs

Abstract

Green roofs play a fundamental role in contemporary urban planning, offering a wide range of environmental, social, and economic benefits that contribute significantly to the development of more sustainable and resilient cities. These systems help mitigate the urban heat island effect, improve air quality, increase urban biodiversity, reduce stormwater runoff, and enhance building energy efficiency. One of the key components of a green roof is the substrate layer, which is responsible for supporting plant growth, retaining water and nutrients, and ensuring proper drainage. Despite its importance, there is no standardized composition for the substrate, as it must be adapted to local conditions and specific project goals. Given this variability, the objective of the present study was to characterize and compare the main physical and chemical properties of three commercial substrates and two composts derived from food waste. The food waste samples were collected from restaurants and underwent different composting processes. The analysis included physical parameters (such as wet and dry bulk density and total porosity) and chemical parameters (pH and electrical conductivity), as well as moisture content, organic matter, and ash content. Among the commercial substrates analyzed, moisture and electrical conductivity values were the most divergent from the recommended standards. In the case of the food waste composts, the composting method was identified as the main factor influencing their properties. The findings of this research offer valuable information for selecting appropriate substrate materials, particularly in the context of green roof implementation, where substrate performance directly affects system success and long-term sustainability.