Cement’s Giant Carbon Footprint

Cement is a dry powder mixed with aggregate, sand, and water to produce concrete. Cement plants manufacture clinker—produced by heating limestone and clay in a rotating kiln at very high temperatures—as the “glue” that binds a concrete mix together.

And concrete is everywhere. It is the most widely used material on earth (last year 30 billion tons of concrete were produced globally) and demand is growing due to urbanization. Traditional cement production is also highly polluting. While cement typically constitutes 10-15% of concrete’s mass in a typical mix, it accounts for 80-90% of its GHG emissions and is a major source of local air pollution. Together, the ubiquity of concrete and the emissions-intensity of making cement means the cement industry would rank as the world’s fourth-largest emitter if it were a country, contributing nearly 8% of global carbon dioxide output. Here at home, cement manufacturing is California’s second-largest industrial source of carbon pollution after oil and gas production.

Clearly, these trends need to change—and fast—if we are going to achieve our climate targets both within and beyond California. Thankfully, momentum is growing to unlock solutions for this essential industry.

Getting to Net-Zero

Cement is often referred to as a “hard-to-abate” industry because a majority of the GHG emissions from making ordinary Portland cement (the industry standard) result from the chemical process of limestone calcination, not the combustion of fossil fuels for energy use. Accordingly, while near-term GHG reductions are possible through fuel switching to lower carbon energy sources (California’s cement plants are the state’s largest consumers of coal and petroleum coke), improving material use and production efficiencies, and enhancing the use of so-called supplementary cementitious materials (SCMs) in concrete, producing carbon neutral or negative cement will require transformative carbon management technologies such as carbon capture and storage.

SB 596 responds to both the near- and long-term abatement opportunities for California’s cement industry by directing ARB to develop a glidepath out to 2045 with strong interim targets to demonstrate progress, including a 40 percent reduction in carbon intensity by 2035. Like the successful process used to develop ARB’s short-lived climate pollutant reduction plan, this will allow for a robust dialogue with industry and other stakeholders to identify key market and regulatory barriers; evaluate a range of solutions across new and existing measures; and prioritize actions that meet essential criteria, such as enhancing California’s competitiveness, improving local air quality, and leveraging state and federal incentives to support economic and workforce development.

Looking Across the Cement-Concrete Supply Chain

For these solutions to take hold, however, California must develop complementary policies to stimulate demand for the use of low carbon cement in concrete. Since public agencies are the largest purchasers of concrete in California (about 40% of all concrete in the state is used for roads and sidewalks), a great place to start is adding concrete to California’s Buy Clean program, which requires contractors to use low carbon building materials to compete for state contracts. Another is to hasten the shift away from prescriptive cement content specifications and toward performance-based specifications, which afford concrete producers the latitude to achieve significant cost and GHG reductions in their mix designs without sacrificing performance. NRDC worked with then-Assembly Member Rob Bonta on a bill to take both of those steps before his appointment to Attorney General, and we are continuing to explore legislative and regulatory pathways to work the demand side of the coin as California’s cement supply gets cleaner under SB 596.

About The Author

 Alex Jackson joined NRDC in 2009 and currently oversees climate law and policy in California. He has led several legislative campaigns for NRDC, including enacting California’s 2030 statewide greenhouse gas emissions limit and extending its cap-and-trade program. His areas of focus include carbon markets, energy efficiency, renewable energy, building decarbonization, and short-lived climate pollutants. He is a board member of the California Foundation on the Environment and the Economy (CFEE), where he sits on the energy steering committee. Jackson holds a bachelor’s degree in environmental policy, history, and government from Cornell University and a J.D. from the University of California, Berkeley. He is based in Sacramento, CA. 

 

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This article originally appeared on OnEarth