One of the oldest industries on the planet, human construction has evolved over thousands of years. From the first stone roadways in Mesopotamia, to towering New York City skyscrapers, mankind continually innovates new ways to construct the built world around us. Today, the pace of human construction is increasing. Experts estimate that the square area of the built world likely will double by 2060.
At the same time, society is grappling with the imminent dangers of climate change. Emissions from the built world alone encompass approximately 27% of greenhouse gases (GHG) released. Accordingly, if civilization is effectively to slow global warming and continue to build the cities of tomorrow, reductions in emissions from the building sector are necessary.
What is Embodied Carbon?
Embodied carbon primarily refers to the carbon-dioxide emissions that are embodied in the building materials, released through the manufacturing, production, and transportation of materials to the construction site. It also refers to the carbon-dioxide that arises from the deconstruction of materials at the end of a building’s life.
Essentially, embodied carbon is the beginning and end part of the total lifecycle carbon analysis of a building. A lifecycle CO2 analysis looks at the construction of a building, to its operational stage (also known as operational carbon), then its demolition. The emissions associated with the operational phase are often reduced through energy efficiency strategies. However, techniques to mitigate CO2 from embodied carbon have historically lagged in comparison . Fortunately, that is beginning to change.
How Does it Relate to Climate Change?
A large source of GHG emissions from embodied carbon are due to two specific building materials: cement and steel. Cement and steel alone comprise over 16% of global carbon-dioxide emissions. Of the building sector emissions, almost half are attributable to embodied carbon. Moreover, because of construction’s impact on material streams from other sectors, reducing embodied carbon has the potential to have a great impact on climate change mitigation overall.
There are currently a few paths for embodied carbon mitigation strategies. The first is to design a building using less carbon-intensive materials and thus opt for alternatives such as cross-laminated timber. Cross-laminated timber is a wood-based building material that has high structural integrity. Additionally, because cross-laminated timber is a wood-based product, it naturally absorbs carbon-dioxide as a tree prior to being used as a commercial product.
Innovations in cement chemistry are also promising in carbon reduction efforts. Today, cement chemistry can be altered through low-carbon alternative ingredients, reducing emissions by up to 50%. Similar innovations are occurring in the manufacturing of steel, where producers are using recycled as opposed to new materials in the making of steel.
An emerging option for developers is the utilization of low-carbon cement. A new cement processing technique has the ability absorb and store CO2 emissions from the atmosphere. The technology works by collecting carbon dioxide through either point industrial outputs, or direct air capture. Captured gas reacts with cement to further mineralize the concrete; a process known as mineral carbonation. If deployed today, mineral carbonation concrete would have the potential to store up to 1 Gigaton of CO2 annually, given the size of the global building market.
Addressing Embodied Carbon through Local Land Use Authority:
The legislatures of most states have delegated the legal authority to regulate land use and building development to local governments: cities and towns. Building codes are typically promulgated by the International Codes Council, legally adopted by state code councils, and enforced by local governments. The power of municipal governments to permit construction techniques and materials such as low embodied carbon cement or tri-laminated lumber varies from state to state. Some state legislatures preempt building code adoption, others permit local code amendment through home rule or charter provisions, or discretion delegated to local code commissioners. The ability to promote sustainable construction practices can be found in broadly construed zoning codes, in the power to impose conditions on development approvals by local boards, or in providing development incentives of various types. Finally, cities and towns can also provide for retrofitting and reusing existing structures, or the use of recycled materials, significantly reducing embodied carbon and fostering more environmentally conscious development.
Today, local governments across the country are using these various sources of legal authority to mitigate embodied carbon from the building sector.
- Marin County, California: In 2019, Marin County, California became the first municipality to enact regulations that limit emissions from embodied carbon. The regulation requires a commitment to an embodied carbon compliance pathway by the developer.
- Gaithersburg, Maryland: Gaithersburg, Maryland updated its building code to incorporate embodied carbon regulations into the building construction standards. Gaithersburg specifically adopted the 2018 International Green Construction Code (IgCC), including provisions such as an assessment of the total life-cycle carbon emissions of a building project, including calculations of embodied carbon.
- Seattle, Washington: Other local governments are creating incentives for low-carbon building, such as Seattle’s Priority Green Expedited program, which shortens construction plan review time for developers that consider opportunities to mitigate embodied carbon emissions.
- Pittsburgh, Pennsylvania: Pittsburgh developed a city-wide deconstruction recycling program that establishes building deconstruction standards, provides for deconstruction and material diversion training for construction workers and developers, and uses an incentive program for private demolition permit applicants to recover and reuse building materials.
The need for low-carbon building is here as are land use strategies for achieving it. Local regulations that mitigate embodied carbon are critical if we are to slow global warming while continuing to build the roads, towns, and city skyscrapers of tomorrow.
This article is part of a series from the Land Use Law Center that explores how local governments can implement Climate Resilient Development (CRD) as defined in the Sixth Assessment Report of the IPCC. CRD requires innovative reform of land use planning and regulation by local governments. The series presents and analyzes numerous local laws and policies capable of adapting to and mitigating climate change to create equitable and sustainable neighborhoods, achieving “sustainable development for all.”
Author: Hailey Pedicano, Rising 3L Land Use Scholar