The need to reduce energy consumption and greenhouse gas (GHG) emissions from the construction of buildings is becoming increasingly urgent. A recent International Energy Agency (IEA) report shows that the sector is struggling to get on track to meet its 2050 Net Zero Emissions (NZE) targets. Moreover, in 2022, buildings consumed 1% more energy than the year before, with electricity accounting for about 35% of buildings’ energy use, up from 30% in 2010.

The IEA’s NZE Scenario finds that energy consumption in buildings needs to drop by around 25% and fossil fuel use decrease by more than 40% by 2030. Similarly, GHG emissions from buildings and construction sites, as well as emissions from the production of building materials such as steel, cement and glass, will also need to come down substantially if the targets are to be met.

Replacing diesel powered plant
One of the key ways to reduce both energy use and GHG emissions on construction sites is to replace diesel powered plant and machinery with greener alternatives. In the UK, a plan is in place under the aegis of the Construction Leadership Council (CLC) to eliminate diesel use on 78% of construction sites by 2035.

An estimated 300,000 items of non-road mobile machinery (NRMM) are in use in the UK. These range in power from 10 kVa to 500 kVa, using some 2.5mn toe in diesel per year. The plan envisages a transition to hydrogen power; other fuels such as biofuels, gas-to-liquid (GTL) and LPG; as well as electricity.

The CLC’s Zero diesel sites route map has been launched to guide the move away from diesel. One of the UK’s biggest construction projects is High Speed Rail 2 (HS2). According to Neil Wait, Head of Environmental Delivery at HS2 and Chair of the Zero Diesel Route Map Working Group: ‘HS2 Ltd has played a key role in the development of the route map and is already making great progress with 19 diesel-free construction sites on the project. This launch is a tangible demonstration of the industry’s shared commitment to radically cut our reliance on diesel.’

One of the key ways to reduce both energy use and GHG emissions on construction sites is to replace diesel-powered plant and machinery with greener alternatives.

JCB takes up 2024 challenge
Meanwhile, plant and machinery supply companies such as JCB Power Systems are making progress in developing a hydrogen engine. This is expected to play a key role in the replacement of diesel-powered machinery. In July 2023, former Energy Secretary Grant Shapps declared himself ‘impressed’ with the company’s early success in developing engines powered by the zero-carbon fuel. He has now challenged JCB to have its super-efficient hydrogen machines working on building sites and farms by 2024.

So far, the company has produced more than 50 prototype engines, and several machines are currently undergoing testing. JCB has also successfully launched a range of battery-electric compact machines, with more than 20,000 units already sold. However, there are concerns about the viability of battery-electric technology across the entire sector. It is widely believed to be largely unsuitable for heavier equipment, due to the higher energy demands and the longer working hours of such machinery in remote locations where access to grid connections is limited.

But while curbing emissions from site machinery will be a positive step forward in decarbonising the construction industry, a joint study by Deloitte and Shell shows that this is only a fraction of the overall task facing the sector. Emissions from the production of construction materials, construction activities and logistics (called embodied carbon) accounted for 5.4 Gt of CO₂ in 2020, or 16% of all global CO₂ emissions.

Across the entire construction value chain, the sourcing and manufacturing of materials represents 92% of embodied carbon emissions. Some 43% of these are attributable to cement, 25% to steel and 24% to remaining materials, such as glass, aluminium, timber and asphalt.

Cement industry ploughs forward
Understandably, the decarbonisation of both cement and steel is now being given top priority by the construction sector. However, there are a number of challenges. In both cement and steel production there is a relatively high energy intensity involved in their production. In the case of cement, there is also the problem of process emissions.

Further barriers include institutional impediments in the form of policy; regulatory issues such as health and safety; infrastructural barriers; land use and zoning issues; and a paucity of investment in R&D. Concrete and cement production has always been for a highly localised market. This means that decarbonisation relies to a large extent on compliance from a wide array of regional stakeholders with varying priorities.

A recent study claims that the full cement and concrete lifecycle, from production to final disposal, accounts for nearly 10% of global energy-related CO₂ emissions. These are rising due to the sheer quantity of concrete, currently 30bn tonnes, that is produced globally.

In 1950–2021, there was a 10-fold per capita growth in cement production, compared to the just three-fold per capita increase in steel production during the same period. The Global Cement and Concrete Association (GCCA) expects a global demand increase from 14bn m³ of concrete in 2020 to approximately 20bn m³ in 2050.

Steel moving towards electric arc furnaces 
Meanwhile, the iron and steel industry is rapidly being transformed by decarbonisation. A recent report from Wood Mackenzie, the global research and consultancy group, describes how electric arc furnaces (EAFs) are helping to revolutionise the sector.

Nippon Steel is the latest company to announce plans to develop ‘super-sized’ EAFs. Replacing highly polluting blast furnaces with EAFs, powered by renewable energy, is among the top three drivers identified by the report. Others include the growing demand for less carbon-intensive feedstocks and the steel industry’s increased use of high-grade scrap through recycling.

However, there are challenges to all three. EAFs, despite recent innovations by Nippon Steel, largely remain small scale; hydrogen-based direct reduced ironmaking (DRI) is unproven and far from commercialisation; and quality issues with scrap continue to limit its use in high-grade steel production. However, progress is being made with the right mix of low-carbon feedstocks, along with the rising availability of renewable power that is fuelling EAF growth.

In light of these developments, Wood Mackenzie sees the EAF share of global steel production increasing from the current 28% to almost 50% by 2050.

Glass sector looks to recycling
The decarbonisation of flat glass production for use in the building industry is also a taking a significant step forward. A report by the European industry association Glass for Europe, which forecasts out to 2050, shows the European Union (EU) flat glass sector has already reduced by 43% its CO₂ emissions per unit of output compared with 1990.

Further improvements are expected to 2050 as glass is identified as an essential tool in decarbonising building stock through the installation of double glazing. ‘Up to 37% of the total energy consumption in the EU building stock can be saved in 2050 thanks to high-performance glazing products,’ says the report.

One area which UK glass industry association British Glass sees as ripe for improvement, is recycling. While the UK glass industry has managed to reduce both absolute and some relative emissions over the previous 13 years, mainly due to the installation of more energy efficient furnace technology and increased cullet (waste glass) use, future potential decarbonisation options must include recycling. ‘Most end-of-life glazing in buildings is not currently recycled and presents a great opportunity for reducing CO₂ process emissions,’ it says.

The Association is engaged with the UK’s Department for Energy Security & Net Zero (DESNZ) in a decarbonisation roadmap that aims for an 80% reduction in CO₂ emissions by 2050.

Inflection point
Decarbonising the construction sector would have a profound impact on global emissions. In addition, it could also accelerate action in a number of other sectors across the value chain. Decarbonisation solutions and initiatives are emerging across the construction value chain. However more still needs to be done – and quicker – to achieve net zero.

According to Shell and Deloitte the sector has now reached an inflection point where it needs to make some firm decisions around decarbonisation. These include:

• Significant carbon reduction in the construction industry’s embodied carbon, mainly from material manufacturing.
• Improving procurement practices and established standards for data and methodologies.
• Investing in alternative raw material inputs. 
• Improving workforce capabilities.

Only if action is taken across this broad front will the construction industry’s net zero objectives be achieved.