Mark Miayoka Högskolan i Halmstad
Urban development demands on construction aggregates are set to rise dramatically over the coming years within the Stockholm region and a significant environmental challenge will be associated with the large flows of construction aggregates and excavated materials in and out of future development projects respectively.
Material banks receive construction and demolition waste (CDW), process this waste and supply recycled aggregates to the construction industry helping to reduce the demand on natural construction minerals. The transportation of these material flows between the material banks and development areas is predominantly by road in the Stockholm region. With the transport sector responsible for almost one third of green-house-gas (GHG) emissions in Sweden, there is a motivation for investigating the environmental benefits of minimising transportation distances of construction aggregates. Quantities of CDW in the form of excavated granular soil and rock from future development locations within a case-study area comprising three municipalities; Botkyrka, Huddinge and Haninge, in the south of Stockholm, have been estimated based on their municipal comprehensive plans up to the year 2030.
This has been done with the assistance of an earthworks estimation tool, the ESAR model, developed by Ecoloop AB. Distances between existing and planned material banks and future development areas together with the estimated material quantities have been combined to approximate total vehiclekilometres for the transportation of these materials under a business-as-usual scenario up until 2030.
A comparison has been made to an alternative scenario of strategically located material banks within the case-study area, whereby a methodology has been developed within this study to strategically locate material banks utilising GIS software ArcMap together with land availability map layers for siting material banks previously developed under a separate related study. In comparison to the business-as-usual scenario, one strategically located material bank within the case-study area reduces total material haulage distances of excavated granular soils and rocks from development areas to the material banks by approximately 42% or 3.67 million vehicle-kilometres, equating to a reduction of 3478 tonnes of CO2e throughout the time horizon of this study. Another output from the ESAR model is the estimated construction aggregate demand for sub-surface earthworks backfilling activities.
A material flow analysis for the strategically located material bank indicates that the material bank is able to satisfy the sub-surface backfilling construction aggregate demand in the form of recycled aggregates throughout its operation. Considering the flow of recycled aggregates back to development areas for backfilling earthworks activities, a total combined reduction of 45% or 5.54 million vehicle-kilometres of material haulage distance is achievable, equating to a saving of 5248 tonnes of CO2e. Reductions in GHG emissions from strategically located material banks are likely to also be significant beyond the boundaries of this study and warrant further research.