Coordinating soil and rock material in urban construction – Scenario analysis of material flows and greenhouse gas emissions
Construction is associated with quarrying as well as heavy transportation of soil and rock materials, in and out of construction sites. Both quarrying and transportation of the excavated materials result in negative environmental impact due to energy use and greenhouse gas (GHG) emissions. Moreover, soil and rock materials of suitable geotechnical quality for construction are a scarce natural resource in some urban regions. These issues have urged the need to optimize the use of quarry materials on-site and thereby reduce transportation. Still, internal flows of soil and rock materials in urban areas have not been well analyzed. This study presents a model to analyze future soil and rock flows in terms of material quality and quantities in urban areas. Furthermore, the study analyses the possibility of recycling excavated soil and rock and thereby reduce transportation and transport-related GHG emissions. The study applies the model in a case study to analyze integrating future residential and non-residential developments and a highway project. The case study revealed that excavated material would be generated in enough volumes to potentially cover the quarry materials demanded for providing stability and permeability to buildings, streets and highway. The scenario analysis showed that provision of strategically located recycling sites for material coordination could reduce the demand for soil and rock transportation as well as transport-related GHG emissions i.e. by 23–36% per area, compared to a business as usual scenario. The study shows that internal soil and rock flows within regions can be modelled by using data from development plans and geological maps. The model results may serve as a basis for decision making regarding strategic material management in urban planning.