Last Updated: Jul 5, 2021
Worldwide, around 4,100 million metric tons of cement were produced in 2019 alone. Joseph Aspdin patented Portland cement in 1824. Since then, experts estimate that we have made enough cement to coat our planet's entire surface with a thin layer of concrete. The Roman Empire made a more rustic type of concrete by mixing lime and volcanic rock. Today's cement industry manufactures its products through a chemical combination of calcium, silicon, aluminum, iron, and other ingredients. Despite the clear advantages that cement and concrete have brought to construction, the global cement industry has an enormous carbon footprint. As a material, it is not often associated with the sustainable building movement.
Procedia Economics and Finance found that the embodied energy in the materials used to build homes produces more greenhouse gasses than the emissions associated with the annual "use-phase emissions." Despite advances in the energy-efficiency rating of dwellings, the energy needed to build the home usually outstrips any potential efficiency gains related to the house's operation. The study discovered that the concrete used in building new homes is responsible for the largest share of emissions.
The International Energy Agency estimates that cement production is alone responsible for upwards of 7 percent of global carbon dioxide emissions. Thus it makes the cement industry a significant contributor to global warming. In addition, cement production has an annual growth rate of 2.5% percent. It is estimated to grow from 2.55 billion tons in 2006 up to 4.4 billion tons by 2050. Without meaningful and far-reaching changes in how cement is produced, it is safe to say that the cement industry will continue to be a significant contributor to global warming.
Despite the enormous ecological cost of cement production, it is hard to imagine a world without cement. After water, cement is the most consumed product by volume used by human beings. We use cement for everything from roads to buildings. Despite its high carbon footprint, it is worth mentioning that cement emissions are significantly lower than if we were to build a structure with steel.
The cement and concrete industry essentially has allowed human beings to make a substitute for rock that can be poured into shapes and forms that benefit our construction projects. Cement is strong and practically waterproof, making it one of the most common materials used for home foundations. Indeed, insulated concrete forms (ICFs) are a popular structural form frequently used in energy-efficient Passive Homes.
Architects and home builders are faced with a dilemma. Cement and concrete are extremely useful and practical for several elements of home construction. Still, they are also a measurable contributor to global warming. Fortunately, innovations in the cement industry are showing promises of more earth-friendly products. We will look at four ways in which the cement industry is slowly becoming more sustainable. They are:
The United States produces around 317 million tons of construction and demolition waste each year; a large percentage of that waste is from concrete. While discarded concrete fills large amounts of landfill space, today, 38 states use recycled concrete as a sturdy road base. In Germany, 89% of concrete demolition waste is recovered and recycled. Cement cannot be separated from the concrete. But, by pulverizing concrete, it is possible to create a useful aggregate for future construction projects. Thus it will limit the need for mining other raw materials and reduce the stress on landfills around the country.
Negative carbon cement is still a work in progress. But, promising companies are working toward developing cement technologies that can capture more carbon than they emit. One innovative company, Novacem, developed an alternative to traditional Portland cement. Whereas Portland cement is made from quicklime, the proposed carbon-negative cement product would be manufactured from magnesium oxide. This compound can absorb carbon dioxide from the air with the addition of water to the cement powder.
Novacem claimed that their product achieves cost and performance parity with traditional cement options. Not only does it pull carbon dioxide from the air, but it also purportedly uses much less CO2 during the process of manufacture. Whereas limestone has to be heated to 2,600 degrees Fahrenheit for cement production, magnesium oxide can be prepared for cement at 1,300 degrees. Novacem was purchased by an Australian mystery company, which they felt needed $50-100M in investment before going to market.
Another company, CarbonCure, based in Nova Scotia, Canada, has developed a process to inject waste carbon dioxide into concrete. This process saves that CO2 from entering the atmosphere and strengthens the concrete. Bill Gates' fund, Breakthrough Energy Ventures, has invested in them - they are already making a big difference in the industry.
The vast majority of concrete used in construction requires some reinforcing agents. Steel rebar is the most commonly used product for this purpose. Steel production is an energy-intensive process that is also responsible for large amounts of greenhouse gas emissions. In Australia, students from James Cook University came up with an alternative reinforcing product that could potentially replace the need for steel.
They manufactured recycled polypropylene fibers from industrial plastic waste into reinforcing agents mixed with Portland cement. By replacing steel with this recycled plastic product, they reportedly achieved 90 percent savings on the overall CO2 emissions associated with steel reinforcements.
The Australian company, Wagners, has created what they term an "Earth-Friendly" Concrete product. This cement alternative uses absolutely no Portland cement. Instead, it utilizes a geopolymer binding system. It is 100% sourced from two typical industrial waste by-products: blast furnace slag (from iron production) and fly ash (from coal-fired power plants). Wagners claim that the total carbon emissions associated with this cement alternative reduce carbon dioxide emissions up to 90 percent compared to Portland cement. Also, it has a much lower embodied energy rating because it is sourced from industrial waste products.
This earth-friendly concrete has moved beyond the planning stage. Over 51,000 square meters of heavy-duty pavement has been constructed at the Brisbane West Wellcamp airport for taxiing runways. Wagners report that close to 9,000 tons of CO2 emissions were avoided using earth-friendly concrete instead of Portland cement for this project.
As technology continues to advance, more and more cement alternatives should continue to emerge. These new options will allow builders and homeowners to continue to enjoy the structural advantages that cement and concrete offer while also vastly reducing traditional cement's ecological footprint.
Tobias runs an agroecology farm and a natural building collective in the mountains of El Salvador. He specializes in earthen construction methods and uses permaculture design methods to integrate structures into the sustainability of the landscape.