The construction industry is a major contributor to global carbon emissions, accounting for a significant portion of the world's greenhouse gases (GHGs). Key materials like cement, steel, aggregates, and bitumen are primary sources of these emissions. As urbanisation continues to accelerate, especially in developing countries such as India, the environmental impact of construction activities is becoming increasingly severe. This situation necessitates the adoption of sustainable construction technologies to mitigate the carbon footprint associated with construction projects. Major contributors to carbon footprint in constructionCement production is a major source of CO2 emissions. This primarily results from the calcination of limestone, a process where limestone (calcium carbonate) is heated to produce lime (calcium oxide), releasing carbon dioxide in the process. Approximately 50% of the limestone mined for cement production is converted to CO2, significantly contributing to greenhouse gas emissions. Moreover, the production of clinker, a key component of cement, is highly energy-intensive, requiring the burning of fossil fuels at high temperatures. This not only results in direct CO2 emissions from the combustion process but also from the chemical reactions involved.Steel manufacturing is another significant contributor to greenhouse gas emissions, especially when using virgin iron ore. The processes involved in extracting and processing iron ore, and subsequently converting it into steel, are highly energy-intensive and rely heavily on fossil fuels. These activities result in substantial CO2 emissions, contributing significantly to the overall carbon footprint of the construction industry. The production of steel involves processes such as coke production, sintering, and blast furnace operations, all of which are major sources of emissions.The extraction and transportation of natural aggregates have considerable environmental impacts. Quarrying operations disrupt natural landscapes and ecosystems, leading to deforestation and habitat destruction. Moreover, the transportation of these materials over long distances contributes to significant CO2 emissions. Bitumen, used extensively in road construction, is another carbon-intensive material. The extraction of crude oil, its refining into bitumen, and the subsequent application processes all contribute heavily to the overall carbon footprint of construction projects.To address the carbon footprint associated with cement production, various sustainable practices and technologies are being adopted. One effective method is the use of alternative fuels in cement kilns. These alternative fuels can include industrial by-products, agricultural waste, and even municipal solid waste. By substituting traditional fossil fuels with these alternatives, cement manufacturers can significantly reduce CO2 emissions. Additionally, the use of electric in-pit crushing technologies minimises the need for diesel-powered machinery, reducing both fuel consumption and emissions. This approach allows for the direct processing of materials at the excavation site, leading to lower energy consumption and environmental impact.Sustainable solutionsRecycling and reusing construction materials is a critical strategy for reducing the carbon footprint of construction projects. Recycled concrete aggregates, sourced from demolition waste, offer a sustainable alternative to virgin materials. By utilising recycled aggregates, the need for quarrying and transportation of new materials is reduced, resulting in lower CO2 emissions. Furthermore, recycled asphalt pavement (RAP) is increasingly being used in road construction. In-situ recycling techniques allow for the recovery of active bitumen and aggregates from existing pavements, significantly lowering the carbon emissions associated with producing and transporting fresh materials.Advancements in crushing and screening technologies have made it possible to process construction materials more efficiently and sustainably. Electric-powered mobile crushers and screening plants, for example, offer a significant reduction in diesel consumption and associated emissions. These machines can be powered by renewable energy sources such as solar or wind, further enhancing their sustainability. Additionally, automated and mobile conveyors for stockpiling materials minimise the use of loaders and dozers, reducing fuel consumption and CO2 emissions. These technologies not only improve operational efficiency but also contribute to a substantial reduction in the carbon footprint of construction activities.Recycling steel is an effective way to reduce the carbon footprint associated with steel production. Machines designed to recover steel rebar from demolished structures play a crucial role in this process. “Recycled steel can be reintroduced into the steel manufacturing process, reducing the need for virgin iron ore and the associated carbon emissions. Efficient steel recycling not only conserves natural resources but also lowers energy consumption and GHG emissions, contributing to more sustainable construction practices,” stated Amol Sinha, Director - Product & Training, Terex India Pvt Ltd.Modern manufacturing technologies are revolutionising the production of construction materials, making them more sustainable. Vertical Shaft Impactors (VSI), for instance, are designed to produce high-quality manufactured sand with reduced energy consumption. These crushers use less energy compared to traditional methods and produce finer, more consistent particles, which are ideal for construction purposes. By improving the efficiency of material production, these advanced technologies contribute to a lower carbon footprint in construction projects.“A good example is the Twin Tower demolition in Noida. While a significant amount of demolition waste was generated, all of it was successfully recycled. This project was widely observed and demonstrated effective waste management and recycling practices,” commented Sinha.Digital solutionsOne of the most promising developments in reducing carbon footprints in construction projects is the use of digital twins and as-built data. Digital twins are virtual replicas of physical structures that allow for real-time monitoring and management throughout the project lifecycle. By capturing as-built data, digital twins ensure that the design-to-build process is seamlessly integrated with actual on-site information, reducing discrepancies and errors that often lead to rework and additional emissions.Traditional construction methods require extensive manual labour for tasks such as surveying and staking, which not only consumes time but also increases carbon emissions due to prolonged use of machinery. Automated machine-guided construction, however, transfers design data directly to construction machines, which then operate based on 3D models. This automation minimises human error, enhances precision, and significantly reduces the need for repeated work.An example of the effective use of construction technology to reduce carbon emissions is the Lucknow Kanpur Expressway project. Mandated by the National Highways Authority of India (NHAI) to use advanced construction technologies, this project saw a substantial reduction in diesel consumption. “By leveraging digital models and connecting them to GPS-enabled graders, compactors, and excavators, the project not only reduced its carbon footprint but also increased efficiency and productivity,” observed Anand Sirohi, Director - Key Accounts & Large Projects, Trimble.In road construction, traditional graders achieve around 25,000 to 30,000 cubic meters per month. However, with the integration of automated systems, this productivity can double, reaching over 60,000 cubic meters. The ability to operate these machines 24/7 without manual guidance further accelerates project timelines, thereby reducing the overall environmental impact.In defence projects, especially those in harsh mountain conditions, automated systems help navigate snow-covered roads accurately, ensuring safe maintenance with minimal environmental disruption. Similarly, in marine projects like the Mumbai Trans Harbour Link, advanced construction technologies enhance both efficiency and accuracy, contributing to a reduced carbon footprint.One of the critical issues in road construction is compaction quality, which affects the durability and longevity of roads. Poor compaction leads to frequent repairs, increasing emissions over time. “Advanced compaction control technologies ensure that roads are built to last, reducing the need for frequent maintenance and associated carbon emissions,” said Sirohi.Software solutions like Tekla and SketchUp play a vital role in promoting sustainability in construction. These tools incorporate standards for sustainable building practices, helping to reduce errors, minimise material waste, and enhance overall project efficiency. For instance, the construction of the Statue of Unity and the Channel Bridge utilised these technologies for precise modelling and fabrication.“To achieve maximum sustainability, it's essential to adopt a comprehensive framework that spans the entire project lifecycle, from planning to renewal. This approach involves using technologies such as GPS, total stations, and automation systems to ensure efficient and sustainable construction practices,” stated Sirohi.  For owners and contractors, the adoption of advanced construction technologies offers numerous benefits. These include increased profit margins, reduced project timelines, and significant cost savings.Alternative solutionsThe primary goal of integrating advanced construction technologies is to reduce the environmental impact of construction projects. By minimising diesel consumption, reducing rework, and enabling round-the-clock operations, these technologies contribute to a substantial reduction in carbon emissions. Currently, most construction equipment runs on diesel engines, but advancements are underway to improve these systems, making them more emission-compliant. These improvements help create sustainable solutions and reduce emissions from tailpipes, including nitrogen oxides and carbon monoxide. Future regulations will likely enforce even stricter emission standards for all construction equipment. “The construction equipment industry is gradually developing electric and hybrid solutions. Although the penetration of these systems is currently low due to high development costs and lack of charging infrastructure in remote areas, the scenario is changing. In the next three to four years, we expect to see more electric and hybrid machines in the field. Costs of electric drives and batteries are projected to decrease, making these solutions more viable,” said Riaz Nawaz, Head of Product Design & Engineering, AJAX Engineering. Alternate fuels like CNG, LNG, and biodiesel present challenges for construction equipment, hence are rarely used. This is due to the difficulties in fuel availability in remote locations and the high costs of engine modifications. However, hydrogen fuel is emerging as a promising alternative. Hydrogen fuel cells, despite being expensive and requiring sophisticated electronics, have the potential to become a key sustainable fuel solution for the construction industry in the next eight to ten years.Nawaz explained, “Using advanced materials in construction equipment can significantly reduce carbon emissions. Traditional construction equipment is made with steel, a major carbon dioxide producer. By adopting higher strength materials, lightweight designs, and composite materials, the industry can reduce steel consumption, decrease fuel use, and enhance overall sustainability.”3D printing3D printing technology is revolutionising construction by allowing for the creation of lightweight, optimised parts with minimal material waste. This technology reduces energy consumption and enables innovative designs. Additionally, the circular economy, focusing on refurbishing and recycling equipment, is gaining traction. Implementing a robust scrapping and recycling policy will help extend the life of construction machinery and minimise environmental impact.Nawaz said, “In the medium to long term, the construction industry will see more technological advancements, including 3D printing of both metallic and non-metallic parts, increased use of carbon fibre, and the adoption of nano materials. These innovations will enhance sustainability by reducing material use and energy consumption.”The transition to sustainable construction technologies is crucial for reducing the carbon footprint of construction projects. By integrating innovative solutions for recycling, energy efficiency, and material reuse, the construction industry can significantly mitigate its environmental impact.(This article is based on the webinar - titled “Construction Technologies to reduce carbon footprint in projects” - organised by FIRST Construction Council on May 16, 2024)