Why is this research needed?

There is an urgent need to reduce embodied carbon in the built environment to meet short-term and long-term climate targets. Buildings contribute a significant proportion of the UK’s carbon emissions and reducing embodied carbon emissions play a key role in the Government’s target to reduce net emissions to zero by 2050. The Climate Change Committee (CCC) reported that the operational carbon emissions of all buildings made up 18% of the UK’s total emissions in 2019. It also reported that 13% of UK emissions in 2019 were from the manufacturing and construction sectors, some of which are associated with the embodied carbon emissions of buildings (https://www.theccc.org.uk/publication/2021-progress-report-to-parliament/).

Activities across the entire construction industries account for over 40% percent of annual global carbon emissions. At least one-quarter of these emissions result from embodied carbon in the built environment associated with manufacturing, transportation, installation, maintenance, and disposal of building materials. For many years, the focus has been on reducing operational emissions from buildings, but most of a building’s total embodied carbon is from the materials and construction process, released upfront and exacerbated during redevelopment. Construction is forecast to increase globally, with one estimate suggesting a 3.9% annual growth to 2030. In the UK housing sector alone, the UK Government set a target to build 300,000 new homes per year by the mid-2020s. ‘Greener buildings’ is one of the points featured in the Government’s 2020 “10 Point Plan for a Green Industrial Revolution”, where it is estimated that developing greener buildings (including both new and existing buildings) has the potential to support 50,000 jobs in 2030, create £11 billion of private investment throughout the 2020s and save a total of 71 MtCO2e of operational carbon emissions between 2023 and 2032 (equivalent to 20% of annual UK emissions in 2019). As such, new technologies that will act to reduce the embodied carbon within the built environment are urgently required. The CarbNET (Carbonation negative emission technology) project supports the UK Government’s net-zero objectives through the development of a new Direct Air Carbon Capture and Utilisation (DACCU) technology to reduce the embodied carbon.

CarbNET will achieve this by evaluating the potential of quarrying and construction waste to be dissolved into high pH solutions that can be utilised on-site to absorb direct air captured carbon dioxide and convert it into value-added solid carbonates for reuse as value-added construction materials to enable the construction industry to reduce the embodied carbon of all built assets and reach net zero. CarbNET will also explore how quarrying and construction waste products can enter a circular chemical economy within the construction industry or be sold to the glass, paper and food manufacturing industries, which use about 50 million tonnes of sodium bicarbonate every year.

What is this research investigating?

This research will directly address the need for advances in the reduction of embodied carbon (emissions associated with all the non-operational aspects of a building such as those from the extraction, manufacture and assembly of a building’s materials and components, its repair, maintenance and refurbishment, and end-of-life activities) within the built environment.

The research has two core aims:
1. Determine the feasibility of using alkali solutions from quarrying and construction waste in conjunction with a CO2 direct air capture system to produce carbonation products.
2. Explore the potential uses of the carbonate products to determine whether there would be sufficient gain to make a viable business model.

The first aim will be achieved by meeting the following objectives:
1.1 Identification of potential sources of alkali bases from industrial by-products to explore the option to use them to sequester CO2 within the context of a circular economy.
1.2 Carefully planned experiments to evaluate the carbonation potential of different concentrations of (i) NaOH, (ii) KOH, (iii) quarry waste and iii) construction waste in water to determine the rates at which CO2 is captured and identify the optimal balance of alkali base concentration/type.

The second aim will be achieved by meeting the following objectives:
2.1 Techno-economic assessment of costs and efficiencies of the entire process and consideration of whether it is scalable.
2.2 Market assessment of the products to determine whether there would be sufficient gain to make a viable business model.

What does the research hope to achieve?

This project will deliver a new Direct Air Carbon Capture and Utilisation (DACCU) technology. This feasibility study, supported by subsequent techno-economic assessments, could, if successful, be scaled up to enable the construction industry to reduce the embodied carbon of all built assets and reach net zero or even negative emissions.