November 2022: Addressing carbon blind spots – redefining waste in the construction industry to reduce carbon emissions

This month’s Smart Infrastructure Blog brings focus to addressing carbon blind spots in construction. CSIC Research Associate Omar Abo Madyan calls for better use of data to reduce waste and enable better carbon decision making.

Is the construction industry on track to achieve net zero? Significant efforts are being made across the construction industry value chain to reduce carbon emissions, with major route maps highlighting how net zero could be achieved. However, the construction process is extremely complex with high uncertainty in processes and material use causing carbon blind spots that are rarely modelled or accounted for – which could hinder industry efforts to achieve net zero targets within the required time frame.

Addressing carbon blind spots and uncertainties will present new opportunities to reduce carbon emissions across the construction value chain and create more accurate carbon models and targets. The recent COP27 concluded that the 1.5C target is hanging by a thread making immediate solutions to further cut construction carbon emissions and improve efficiency and productivity needed now more than ever.

Addressing carbon blind spots and uncertainties will present new opportunities to reduce carbon emissions across the construction value chain and create more accurate carbon models and targets. The recent COP27 concluded that the 1.5C target is hanging by a thread making immediate solutions to further cut construction carbon emissions and improve efficiency and productivity needed now more than ever CSIC Research Associate Omar Abo Madyan, Dep. of Engineering.

Identifying carbon blind spots – what is waste?

The term waste in the construction industry is predominantly ascribed to physical waste that ends up in a skip and eventually in landfill. However, throughout the literature in the field of quantitative and qualitative waste management, numerous definitions of waste are considered across various industries. Following lean manufacturing principles, waste can be defined to include over-production, unnecessary transportation, inventory, displacements, waiting, over-processing, and defects. Current research at CSIC is applying the concept of waste from lean manufacturing to redefine waste across the construction industry, to understand the true efficacy of material value chains. Any material that is consumed but does not provide a useful function nor fully utilised should be defined as waste. Using zero loss yield analysis (ZLYA) provides a continuous improvement approach based on zero loss manufacturing and compares an actual performance of a system/process to a first principle best performance. Commonly used to tackle throughput, cost and labour productivity, ZLYA was adapted and developed to investigate the inefficient use of materials. The main philosophy is to find how/where the material is being used and how much of that material provides value to a certain system/process, thus accounting for carbon blind spots.

However, success depends on obtaining accurate data sets across the value chain. This has proven to be challenging in the past as data recording processes have not seen significant improvements across the construction industry and some processes, such as delivery tickets, are still paper based. This can hinder understanding of the magnitude of waste and the process of determining its root causes. While not all waste may be recoverable, estimating the total waste in the process also allows for an accurate assessment of carbon emissions/models and can identify uncertainties in current practices for calculating carbon emissions. Where current practices assume material waste factors of 2.5-5%, the statistic is extrapolated from either outdated studies or from small datasets that don’t convey the true extent of inefficiencies.

Improving efficiency of concrete

Concrete waste is mainly considered as concrete left in wagons after the pour or the material which ends up at landfills from construction and demolition, but such values are rarely recorded or measured. By applying ZLYA to the value chain of concrete to compare the actual performance of concrete systems and processes to a first principle best performance, it is possible to identify inefficient processes that would otherwise be deemed business as usual and remain unchallenged and unchanged. This is achieved by collecting data using digital tools to analyse the characteristics and material volumes required at the design stage to the characteristics and material volumes used in an asset or structure. The discrepancy between the values highlights the extent to which concrete is providing value in the system, and further establishes data gaps on how and where concrete is used. This also addresses the uncertainties in carbon models that are based on inaccurate assumptions and incomplete datasets.

CSIC’s research using the ZLYA methodology has highlighted several issues including over-ordering, rework, rejected concrete, over-specification, concrete batching accuracy and waste. Results to date have shown high inconsistencies between design volumes and how much concrete is consumed. The yield of concrete – the amount which was actually used efficiently on site – varied between 61% and 97% for individual concrete components, while delivered concrete strengths could be more than double the required design strengths.

Such inconsistencies result in a waste of valuable resources and directly increase carbon emissions due to higher cement content. These valuable insights from data can immediately inform better carbon choices, improve best practice methods, and reduce the associated cost of using more materials than necessary. Without relying on new unrealised technologies, this research will apply learnings from concrete to other materials and processes across the industry to influence material consumption, design codes and standards and produce more accurate carbon models.

References

A. Bennett, Reducing the Impact of Construction Through Application of Production Engineering Principles, Masters Thesis, University of Cambridge 2021

A. Yildirim, A Zero Waste Future in the Construction Industry: Minimising Material Consumption through Digitisation, Masters Thesis, University of Cambridge 2022