Reducing the environmental impact of distribution centres

Abstract

The climate emergency calls for a global shift towards a low-carbon economy, to preserve natural resources and biodiversity, while limiting global warming and its consequences. This project focuses on the impact of distribution centres, intended for the storage of commercial goods. Warehouses are characterised by large flexible spaces and simple structural systems, most often with steel or concrete frames aiming at efficiency and low costs. The aim of this research is to create a sustainable single-storey warehouse with a significantly lower environmental impact compared to reference designs with steel and concrete frames. Considering a new-build project with no reuse of existing elements, a meaningful target for embodied carbon reduction is set to 50% of the environmental impact score of reference steel and concrete warehouse designs.
A selection of sustainable design strategies are investigated, giving insight into which actions designers shall take in priority to effectively reduce the embodied carbon of a warehouse. Reducing upfront emissions (LCA modules A1-A3) requires looking into short-term sustainability measures like reducing material use or using low carbon alternatives wherever possible. Replacing fossil-based products by renewable carbon sequestering materials like timber or other biobased alternatives contributes to lowering the impact of a building, by storing biogenic carbon for the lifespan of these elements. A sustainable use of wood presumes that its design lifespan is at least equal to forest rotation periods to maintain or increase the forest timber stock, combined with sustainable forest management practices. Biogenic carbon storage may be extended by designing for long-term reuse or recycling. Greening the envelope of a building takes advantage of ecosystem services provided by vegetation, like improving air quality, enhancing thermal performance or supporting biodiversity. Many systems can be applied on facades and roofs, depending on project-specific requirements (plant species, layout, load-bearing capacity), to effectively introduce vegetation in the built environment.
The first design step investigates the embodied carbon reduction potential of substituting steel or concrete by timber in the load-bearing frame of a warehouse. Reference steel and concrete structures are selected, and baseline timber designs are created with similar geometrical characteristics and stability systems, to compare their environmental impact on a fair basis. The second design step of the research aims at further reducing the impact of not only the frame, but also other parts of the timber warehouse (foundation pads, floor slab, envelope). Big ticket items responsible for the most impact are identified and tackled in priority: in both timber designs, the floor slab and envelope are responsible for the largest share of embodied carbon. Based on the results of design steps 1 and 2, the 50% embodied carbon reduction target can be achieved by substituting steel or concrete in the frame by timber (-31%), replacing sandwich panels on steel supports by biobased materials in the envelope (-13%), and reducing the floor slab thickness by 50mm (-7%), when considering only fossil emissions. If biogenic carbon storage is accounted for, using biobased materials in the frame (-65%) and in the envelope (-58%), without modifying the floor slab, results in a carbon positive warehouse design. These results are only valid assuming long-term carbon storage in biobased materials, supported by circular design measures. Greening the envelope also contributes to making warehouses more sustainable, provided that benefits from ecosystem services outweigh environmental costs from additional materials.