Environmental Measures and Efficiency! 5 Ways to Simultaneously Reduce CO2 and Costs at Construction Sites

Introduction

In recent years, the civil engineering and construction industry has been required to implement environmental measures such as CO2 emission reductions and resource conservation. At the same time, streamlining construction operations is an unavoidable issue in responding to labor shortages and rising costs. Traditionally, environmental consideration and efficiency/costs have often been seen as a trade-off. However, by leveraging the latest technologies and innovations, there are increasing cases where environmental impact reduction and improvements in construction efficiency and cost savings can be achieved together.

This article introduces five concrete methods for a wide audience—from major contractors to small and medium-sized construction companies, municipal engineers, and site managers and environmental officers—to simultaneously reduce CO2 and costs at construction sites. From introducing energy-efficient heavy equipment and recycling construction by-products to optimizing construction through ICT, adopting decarbonized materials, and improving management efficiency with smart surveying, each method’s effects, implementation examples, introduction costs and benefits, and related technologies are explained in detail.

1. Introducing Energy-Efficient Heavy Equipment and Improving Operating Efficiency

The first method is to introduce energy-efficient construction machinery with excellent fuel economy and improve the operating efficiency of heavy equipment. Heavy machinery used on construction sites, such as hydraulic excavators and bulldozers, consume large amounts of diesel fuel and emit significant CO2. Therefore, switching to the latest models equipped with engine energy-saving technologies or to hybrid and electric machinery is effective.

For example, major manufacturers are accelerating the electrification of heavy equipment toward decarbonization. Komatsu obtained GX construction machinery certification from the Ministry of Land, Infrastructure, Transport and Tourism in 2023 for seven electric construction machines, including a “battery-powered electric hydraulic excavator.” Such electric machines can not only reduce CO2 emissions during operation to virtually zero, but also bring benefits to the surrounding environment through lower fuel costs, reduced noise, and lower vibration. Hitachi Construction Machinery offers the electric excavator “ZE” series up to medium size, and Tadano released the world’s first all-electric crane, among other developments, showing that energy-efficient heavy equipment is spreading across the industry.

Energy-efficient heavy equipment tends to have higher initial costs than conventional machines, but over the long term cost benefits are expected through fuel savings and reduced maintenance costs. In fact, a quarry site in Sweden reported that introducing a fleet of electric heavy machines reduced CO2 emissions by about 98% compared to conventional equipment. Additionally, lower noise enables night work, improving construction flexibility and providing efficiency benefits.

Moreover, operational improvements can improve fuel efficiency even with existing equipment. For example:

• Thorough implementation of idling stop: Stop the engine during standby to reduce unnecessary fuel consumption and emissions.

• Practice eco-driving: Avoid sudden starts, rapid acceleration, and harsh braking; operate at appropriate output for the task to improve fuel economy.

• Proper maintenance: Regularly change oil and air filters, manage tire air pressure, and perform routine maintenance. Preventing performance degradation and fuel efficiency decline contributes to CO2 emission reductions.

• Digitalization of operation management: Equip heavy equipment with IoT sensors or telematics devices to visualize and manage operating time and idling time for operational improvements.

By combining the introduction of the latest equipment with operational improvements, it is possible to significantly reduce fuel-derived CO2 emissions while achieving fuel cost reductions and shortened work times. Utilizing subsidies and tax incentives can also reduce initial introduction costs, so active consideration is recommended.

2. Reuse of Construction By-products and Resource-Circulating Construction

The second method is to reuse construction by-products generated during work and implement resource-circulating construction. Civil and building works generate a wide variety of by-products, such as excavated soil, concrete and asphalt rubble from demolition, and waste materials (wood, metal, etc.). Rather than disposing of these as industrial waste, effectively using them on-site or off-site as much as possible can yield significant benefits in terms of both environmental impact and cost.

Specifically, the following reuse measures are being implemented:

• Effective use of excavated soil: Large volumes of soil generated from excavation (construction-generated soil) can be reused for backfilling or embankment material on-site. Matching services provide soil for other development or reclamation projects, reducing the cost and CO2 of transporting and disposing of unwanted soil.

• Recycling of concrete rubble: Demolition concrete is crushed and used as recycled crushed stone (recycled crusher run) or recycled sand for road base materials or backfill. This reduces the amount of new quarrying and can lower disposal costs.

• Recycling of asphalt waste: Removed asphalt can be reheated and remixed into recycled asphalt concrete for pavement reuse. Increasing the recycling rate reduces the use of new asphalt mixes.

• Reuse of construction wood waste: Demolition wood can be chipped and used as raw material for plywood and paper, or as fuel for biomass power generation. Temporary works materials such as shoring or formwork should be reused as much as possible to suppress new wood consumption and waste.

• Sorting and 3R of other waste materials: Metal scraps, glass, ceramics, and other recyclable materials should be carefully sorted and sold or reused as resources, such as steel scrap or glass raw materials. Installing on-site separation yards for mixed waste can increase the recycling rate.

In Japan, the “Act on Recycling of Construction Materials in Construction Works (Construction Recycling Law)” was enacted in 2002, requiring recycling of specific construction material waste such as concrete rubble, asphalt/concrete rubble, and construction-generated wood for projects above a certain scale. Against this background, general contractors prepare “construction by-product utilization plans” for each site and work to increase the utilization rate of recycled resources. The Ministry of Land, Infrastructure, Transport and Tourism’s Construction By-product Information Exchange System (COBRIS) enables real-time information exchange on by-products and searches for facilities that can use them, supporting matching between sites that generate soil or waste and those that need them.

The environmental benefits are clear: reducing CO2 emissions from new resource extraction and waste disposal, preventing illegal dumping, and extending the life of final disposal sites. Economically, reductions in soil disposal costs and new material costs, and revenue from selling waste materials can be expected, contributing to overall construction cost reduction. For example, in a large-scale tunnel project where 1,000,000 m^3 (35,314,666.7 ft^3) of construction sludge was used for land reclamation in Osaka Bay, disposal cost reductions on the order of several billion yen were reported.

A key to successful resource-circulating construction is incorporating reuse from the planning stage. Use BIM/CIM to simulate the overall material input and by-product generation for the project, and pre-plan reuse destinations and storage locations. Coordination with subcontractors and other sites is also important. This establishes a workflow that makes the most of generated materials and enables sustainable construction in both environmental and cost aspects.

3. Construction Optimization through ICT (Equipment Allocation and Route Shortening)

The third method is to optimize construction processes by utilizing ICT (Information and Communication Technology). Visualize and automate equipment movements and placement, and material transport routes using digital technology to eliminate unnecessary movements and waiting time. This field, promoted as part of the Ministry of Land, Infrastructure, Transport and Tourism’s “i-Construction” and construction DX initiatives, delivers significant effects in reducing environmental impact and improving productivity.

Some concrete ICT use cases include:

• Machine guidance and machine control (MG/MC): Use GPS and 3D design data to automatically control blades and buckets of heavy equipment for precise grading and excavation. This can eliminate manual stakeouts and repeated checks, shortening work time. In one experiment, using an ICT hydraulic excavator shortened direct working time by about 43% compared to conventional methods, and because one machine operator could complete the work, manpower required was reduced to one-third. This leads to significant reductions in fuel consumption and CO2 emissions.

• Visualization of equipment operation: Systems exist that equip on-site machinery with GNSS transmitters and display each machine’s position and trajectory in real time on a cloud-based 3D site model. Toda Corporation uses the [Heavy Equipment Operation Visualization System](https://www.toda.co.jp/tech/cutting/machinery.html) to grasp bulldozer and dump truck travel routes and standby times at a glance, helping to optimize equipment allocation and adjust the number of units. As a result, fuel use per task has been reduced, achieving shorter construction periods and cost savings.

• Route optimization for material transport: Coordinate with subcontractors to optimize dump truck routes and schedules using ICT. By using map apps and logistics management systems to instruct routes and time windows that avoid congestion and waiting time, truck travel distance and idling time can be reduced. Coordinating with nearby sites for joint material deliveries can also reduce empty return trips and the number of trucks required.

• Simulation of construction plans: Simulate construction steps and equipment movements in software in advance to design efficient construction sequences. Reduce waiting and overlapping tasks between processes and complete the work with minimal movement. If operators are instructed based on simulation results, on-site trial-and-error is reduced, preventing waste of fuel and time.

The benefits of ICT-based construction optimization lie in the fact that CO2 emissions reduction and cost savings come hand in hand. Reducing unnecessary movements reduces fuel consumption, and shorter working times save labor and machine costs. Digitalization also enables construction that does not rely on experience or intuition, an important secondary effect for maintaining quality and efficiency amid shortages of skilled workers. Initial investment is required for surveying drones, GNSS equipment, and dedicated software, but national and local government subsidies and scoring systems for ICT-utilized projects are available, so phased introduction while leveraging support measures is recommended.

4. Adoption of Decarbonized Materials and BIM Integration

The fourth method is to switch construction materials themselves to decarbonized types and maximize their effect through integration with BIM technologies. A significant portion of CO2 emissions associated with construction sites actually occurs during the manufacturing stage of materials. Cement production and steelmaking are particularly energy-intensive, so reducing the embodied carbon (CO2 emissions during manufacturing) of these construction materials is a critical issue for carbon neutrality.

In recent years, various low-carbon construction materials have been developed and offered. Examples include:

• Low-CO2 cement and concrete: Eco-cements that blend blast-furnace slag or fly ash (coal ash) with cement can reduce manufacturing CO2 by 30–40% compared to conventional products. Special concretes that absorb CO2 during curing (CO2-adsorbing concrete) are also being commercialized.

• Green steel: Development is progressing on “green steel,” which greatly reduces CO2 emissions by using hydrogen instead of coal in steelmaking. Replacing structural steel for buildings and bridges with steel produced by such methods in the future can yield indirect CO2 reduction benefits.

• Promotion of wood use: Wood stores carbon absorbed during growth, providing a “carbon storage” effect. The use of engineered timber (CLT, etc.) instead of steel or concrete in medium to large-scale buildings is spreading. In civil engineering, actively using wood for temporary structures and landscape facilities can reduce concrete usage.

• Use of recycled materials: Actively incorporate the aforementioned recycled construction materials into new materials. For example, recycled aggregate concrete reduces the use of virgin aggregate and, if it meets quality standards, can be applied to building structures. Recycled asphalt reduces the need for new oil-derived asphalt.

However, low-carbon materials are currently more expensive, and their widespread adoption requires support measures such as preferential use in public works or leveraging carbon pricing revenues. It is also necessary to stimulate demand across the supply chain, not just use the materials themselves. As prices are expected to fall and environmental regulations are likely to tighten in the future, it is important to start trial adoption now to accumulate know-how.

BIM (Building Information Modeling) and CIM (Construction Information Modeling) are tools to use here. By linking material information to 3D models of buildings and infrastructure in BIM/CIM, it is possible to visualize embodied carbon for each component from the design stage. For example, it becomes easy to simulate CO2 reductions from switching from reinforced concrete to timber or to compare the effects of replacing a conventional concrete with a low-carbon concrete. Maeda Corporation developed the LCA evaluation system [CO2-Scope](https://www.maeda.co.jp/news/2024/07/05/5504.html) linked to BIM data, enabling rapid calculation of carbon footprints at the design stage to inform optimal material choices.

Furthermore, BIM contributes to appropriate material ordering and construction planning. Calculating detailed quantities prevents overordering, reducing unnecessary material production, and promoting prefabrication and standardization helps suppress on-site waste. Sharing information on BIM among designers, contractors, and manufacturers allows understanding the characteristics (strength and construction conditions) of new decarbonized materials in advance and optimizes construction sequencing—a significant advantage.

In short, the approach is to promote decarbonization and efficiency simultaneously through both materials and digital technology. Adopting low-carbon materials reduces environmental impact over the entire lifecycle, including eventual disposal and recycling, and BIM integration makes it feasible to implement these choices on-site without difficulty.

5. Smart Surveying and Management Efficiency (Simple Surveying with LRTK)

The fifth and final method is to introduce smart surveying technology to improve construction management efficiency. Tasks frequently performed on construction sites—such as surveying, as-built management, and quality inspection—can be performed easily and with high accuracy using the latest devices and software. This can greatly reduce the time and effort required for site management, leading to shortened construction periods, error prevention, and cost reductions.

Of particular note in recent years are simple surveying systems that use smartphones and tablets. For example, the startup Reflexia developed a device called “LRTK,” a pocket-sized RTK-GNSS receiver that attaches to an iPhone/iPad. With LRTK, anyone’s smartphone can be transformed into a versatile surveying instrument with centimeter-level accuracy (half-inch accuracy). Tasks that used to be performed by specialist surveyors with total stations can be completed quickly by site managers or workers alone.

Smart surveying devices like LRTK have the following features and benefits:

• High-precision position measurement: The RTK method enables positioning with errors ranging from several centimeters to several millimeters. Using this for setting reference points and as-built measurements drastically reduces surveying errors that cause rework.

• Easy operation: Measurements can be taken with intuitive smartphone app operations, such as pushing a button. Because no specialized knowledge is required, these tools are easy to use even on sites lacking experienced surveyors.

• Portability and responsiveness: The small device weighs only about 125 g, so it can be carried in a pocket and used whenever needed. Being able to “measure whenever you want” increases measurement frequency and speeds up progress management and inspections.

• Multifunctionality: Beyond simple coordinate surveying, combining with a smartphone’s built-in LiDAR enables point cloud measurement, AR display can mark design positions (staking out), and diverse on-site needs can be met. For example, visualizing the location of buried objects in AR while excavating helps prevent accidental excavation and improves work efficiency.

• Real-time sharing: Measured data can be automatically uploaded to the cloud and shared in real time with the office and clients. Compared with the conventional method of taking paper drawings back and doing manual calculations and reports, data can be checked and used immediately, speeding decision-making.

Introducing smart surveying tools can be described as DX for site management. While it may seem indirect from an environmental perspective, if surveying and inspection efficiency reduces work time and personnel, it leads to overall energy consumption reduction on the site (shorter operating time for machinery and vehicles). Increased measurement frequency also reduces mistakes and rework, preventing unnecessary use of materials and fuel.

Beyond smart surveying, various IoT and AI technologies are emerging in site management. For example, installing sensors to automatically monitor concrete curing temperature, noise, vibration, and dust concentration, or using AI analysis of drone aerial images to check as-built conditions and progress. Advancing such smart site management measures together can reduce management burdens and improve quality, contributing to labor-saving and energy-saving outcomes.

Conclusion

We have introduced five methods to simultaneously reduce CO2 emissions and costs at construction sites. Improvements in fuel economy through the introduction of energy-efficient heavy equipment, waste reduction through recycling construction by-products, elimination of waste through ICT-enabled construction, fundamental carbon footprint reductions through adoption of decarbonized materials, and operational efficiency through smart surveying and management—each method is effective on its own, but combining them generates synergistic effects.

With the calls for carbon neutrality and the SDGs, environmental measures are now a corporate social responsibility, and efforts toward environmental consideration are evaluated even in public works bidding. Fortunately, advances in digital technology and the advent of new materials mean that “what is good for the environment can also raise productivity” in more cases. Use the methods presented here as a reference and start implementing what you can at your own sites—“starting with what’s possible” and “visualizing as you go.”

Balancing the environment and efficiency is the key to a sustainable construction industry. Being able to reduce CO2 and costs simultaneously directly strengthens your company’s competitiveness. The future construction site will be environmentally friendly and smart as the norm. Toward such a future, please begin taking steps, one at a time.