Cut the carbon: Circularity, smart material choice and innovative methods

Traditionally, the responsibility for decarbonization strategies has been carried by designers, architects and planners, whose innovative approaches to sustainable design have paved the way for reducing the environmental impact of the built environment. However, it's becoming increasingly clear that general contractors also wield significant and transformative power in this area.

Responsible for executing the visions of designers, contractors occupy a central position in the construction value chain, and h­­­ave a tremendous responsibility and opportunity to drive this transformation. A wealth of strategies exists to help contractors reduce projects’ embodied carbon, the upfront carbon emissions associated with materials and construction processes throughout a building's life cycle.

Let’s have a look at some of the key opportunities.

Maximize adaptive reuse of buildings

Every year, the construction and demolition (C&D) sector generates a staggering volume of waste – over 600 million tons annually in the United States, of which about 145 million tons end up in landfills. That makes C&D debris the single largest waste stream in the country, eclipsing even municipal solid waste. Demolition alone accounts for more than 90 percent of this debris, highlighting just how much of our built environment is being discarded rather than renewed.

Demolishing a building can be a complex and wasteful process. The practice of simply tearing down and rebuilding has led to a major environmental issue, as demonstrated by the staggering amount of waste generated by the C&D industry. While there is a need for new construction, it is crucial to maximize the opportunities for adaptive reuse, which refers to the practice of creatively transforming existing buildings and structures for new uses, rather than demolishing them and constructing new ones. By creatively transforming existing structures, we can not only preserve architectural heritage but also dramatically reduce the environmental footprint of new construction.

Building reuse almost always yields fewer lifecycle environmental impacts than new construction when comparing buildings of similar size and functionality. It can take between 10 and 80 years for a new, energy-efficient building to overcome, through more efficient operations, the negative climate change impacts created during the construction process. Therefore, it is important to utilize opportunities for adaptive reuse.

The University of Portland’s Shiley-Marcos Center for Design & Innovation in Portland, Oregon, is a great example of adaptive reuse. This project reuses the main structural system of a previously existing physical plant located on campus, turning it into a hub for academic creativity and learning for students, faculty and community.

An adaptive reuse strategy and reuse of the main structural system greatly reduced the amount of new concrete and rebar, achieving a 42 percent reduction in embodied carbon emissions compared with a new construction alternative.

Reduce embodied carbon emissions through circularity and material reuse Circularity offers a powerful solution to tackle embodied carbon emissions in the construction industry. Closing the loop on material life cycles eliminates the need to extract, process and transport virgin materials, while reducing waste generation.

The Portland International Airport's Terminal Core Redevelopment project, built by the Hoffman-Skanska Joint Venture, is a perfect example of this approach. Pursuing LEED Gold certification, the project features an iconic 36,000 square meter (nine-acre) long-span mass timber roof constructed from wood sourced from local and regional forests, promoting sustainability in aviation infrastructure.

The project team also implemented circularity strategies and engaged with local recyclers to transform the project’s wood waste into finished products and wall panels, minimizing landfill use, and using salvaged lumber for miscellaneous needs, reducing overall reliance on virgin materials.

The Concourse Connector passageway at Portland. Film by Nick Grier Photography

And instead of building a new temporary bypass during the five-year long construction, the team creatively relocated and  repurposed the 213 meter-long (700-foot) Concourse Connector. This structure, which was slated for demolition, was cut in half and reused as a temporary bypass passageway to enhance airport passenger experience and help people move safely around the construction area at the airport’s core.

These reuse strategies positively contribute to the project’s sustainability goals to prevent waste and reduce the embodied carbon footprint of the project while achieving significant cost and time savings.

Procure low-carbon materials and transition to low-carbon construction

General contractors play a vital role in informing design choices and procuring low carbon alternatives, identifying opportunities to minimize transportation and construction carbon emissions, and tracking the realized embodied carbon impacts at project completion.

Our team at Skanska co-conceived and developed the Embodied Carbon in Construction Calculator (EC3) tool in partnership with the Carbon Leadership Forum and nearly 50 industry partners, including Microsoft, to tackle embodied carbon in our value chain. This free, open-access tool is helpful for AEC (architecture, engineering and construction) professionals, particularly general contractors, enabling them to make low-carbon procurement and smart transportation and construction decisions.

The Norton Rose Fulbright Tower (formerly 1550 on the Green), a Skanska-developed and built premium office building in Houston, Texas, is a great example of the power of the EC3 tool. This Class-A  building achieved LEED Platinum, WELL Platinum and WiredScore Platinum certifications. The Skanska team used the EC3 tool to identify low-carbon materials, guide smart procurement strategies, and reduce the project’s embodied carbon emissions by around 45 percent.

Contractors can easily identify low-cost and no-cost solutions for low-carbon materials and achieve such embodied carbon savings at cost premiums of less than 1 percent. Tackling the emissions on construction sites is crucial for general contractors to reduce their environmental impact. In the United States, our Skanska teams have started to switch from using petroleum diesel to renewable diesel in construction equipment and vehicles in select projects on the West Coast and have been expanding the use of the alternative fuel to other regions and projects.

Renewable diesel is nearly chemically identical to petroleum diesel. According to the California Air Resources Board, using renewable diesel provides a 40-50 percent reduction of GHG from well-to-wheel emissions and produces specific measurable reductions in tail-pipe emissions versus fossil-based diesel.

As part of our climate plan, Skanska USA Civil has been piloting pre-production models of various pieces of all-electric equipment and all-electric vehicles in select sites to further reduce emissions on our construction sites.

In September, our Building division in the USA announced that all offices must purchase electric vehicles when adding to our company fleet, or replacing vehicles. This is part of the Skanska Group goal of a 70 percent reduction in operational emissions by 2030 and our commitment to achieve net-zero carbon emissions by 2045, based on a 2015 baseline.

The path to decarbonization is paved with collaboration and innovation, and contractors hold a significant responsibility. Through circular practices, smart material choices and innovative construction methods, contractors can significantly contribute to the sustainability of the built environment. Ignoring this responsibility isn't just an ethical misstep, it's a business risk.