Concrete panels are the most sustainable building method.

Precast concrete is composed mainly of water, aggregate and cement. Admixtures and reinforcement may also be needed for different manufacturing or product physical or structural purposes. Architectural precast includes architectural cladding and sandwich panels with re-constructed stone, brick-facing or cast stone finishing. Production of specific types of architectural precast requires a wider range of materials than grey concrete (such as natural stone or brick facing, polishing or etching acid) and can be slightly more labour/ energy intensive. 

Reference: Architectural & Structural Precast Association (ASPA) Fact Sheet

At end of life, concrete can be fully recycled to create new construction materials. When mixed with other demolition waste it forms hardcore or, if separated out, can be crushed for use as a recycled aggregate in new concrete. There is little evidence that any hard demolition and construction waste is sent to landfill in the UK.

It is a little known fact that roughly 20 per cent of the direct CO2 emissions from the manufacture of UK cement will be reabsorbed during its life cycle. The process is called recarbonation and, in whole-life terms, it reduces the CO2 footprint of concrete and other materials containing cement. Published figures for the embodied CO2 of cement do not take this into account as they are generally limited to the manufacturing process i.e. cradle to factory gate. The speed of CO2 uptake depends on a number of factors including the type of concrete and the surrounding environment. Lightweight blocks and low strength concrete recarbonates relatively quickly. High strength concrete takes longer, with most of the recarbonation occurring later in its lifecycle i.e. after demolition and crushing.

Reference: MPA The Concrete Centre - Fabric for Future report