The quest for lower-carbon data center construction materials continues.
In wake of fellow cloud giant Microsoft announcing earlier this month a renewal of its ongoing commitment to low-carbon concrete mixtures, this time with a mix employing microalgaes -- and companies such as Compass Datacenters this year highlighting an entire program devoted building sustainability into its construction processes -- Amazon Web Services (AWS) this week proclaimed that it is using lower-carbon concrete and steel to build its data centers, and is taking efforts to make these materials more available across the entire global construction industry.
AWS said it now operates 43 data centers globally which have been constructed with either or both lower-carbon concrete and steel -- more than double the company's previous reported total as of just last year.
From its construction so far this year of 27 data centers using lower-carbon steel and concrete, the company reports that it saved more than 22,000 tons of carbon dioxide equivalent (tCO2e). That's equivalent to the amount of carbon emissions resulting from the charging of more than 2.6 billion smartphones, as reckoned by AWS's statement.
4 Keys to Lower-Carbon Data Center Construction
AWS identified four tenets of its continued drive toward progress on sustainability in data center construction via the use of lower-carbon building materials:
1.) By “designing-out” the overall amount of steel and concrete it uses. By continuously evaluating its design criteria for everything from server racks to office spaces and storage rooms, AWS said it has been able to find opportunities to reduce the total amount of materials, such as steel and cement, needed to support its buildings.
By way of example, the company said it recently identified an opportunity to change the air system in its data center designs to reduce the amount of materials used in new building structures. By removing the concrete topping from a mezzanine floor and only using steel beams, AWS said it now saves roughly 115 metric tons of carbon dioxide equivalent per data center.
2.) By testing lower-carbon cement alternatives. AWS notes that, as cement accounts for roughly 90% of concrete's embodied carbon, manufacturers are developing mixes with lower embodied carbon by incorporating recycled byproducts (such as slag smelted from recycled ores and metals) from other industrial processes to replace ordinary cement. Another new alternative cited by AWS is to replace ordinary cement with Portland-Limestone Cement (Type IL), which contains a higher ratio of raw limestone to ordinary cement, and a lower embodied carbon. When used in combination, AWS contends that these two methods can reduce carbon emissions by up to 50%.
The company emphasized its work with suppliers, including Ash Grove, Holcim, and Titan America, on trial batching the new mixture to ensure that strength and performance standards, such as water-to-cement ratios, air content, and shrinkage limits, are satisfied. After trial batching a mixture for a data center construction project in northern Virginia, AWS said its concrete supplier was able to replace 40% of the ordinary cement with slag, while still meeting the project’s schedule constraints. Owing to the reduced cement content, the company was able to cut embodied carbon in the cement mix by more than 30%.
3.) By encouraging its suppliers to incorporate lower-carbon steel into their supply chains. As reckoned by AWS, globally, the most popular manufacturing method for steel is the basic oxygen furnace (BOF), which burns coal or gas. But rather than relying on fossil fuels, steel can also be produced in electric-arc furnaces (EAF) that use scrap steel and are powered by energy from the grid—in some cases from renewable sources. AWS reports that in 2021, it began purchasing EAF steel for its data centers, "which commonly amounts to half of the embodied carbon compared to BOF steel production, and can even achieve as low as one-fifth," according to the company's statement.
Using higher-strength structural steel, made by cooling the metal quickly during manufacturing, is another way to reduce the carbon footprint of a data center. Such steel has a higher strength-to-weight ratio, allowing a smaller quantity of material to deliver the same function, without increasing the embodied carbon. By incorporating higher-strength steel into its structural designs, AWS said it has achieved a weight reduction of 70 tons of steel for each two-story data center.
4.) By investing in innovative technologies to drive future carbon reductions. As popular cement replacements, such as slag, are byproducts of coal-fired manufacturing, and the supply of these replacements will dwindle as the world transitions away from fossil fuels, Amazon said it is helping to bridge the innovation gap in decarbonizing data centers by investing in lower-carbon concrete and steel technologies through the Climate Pledge Fund, a $2 billion venture investment program supporting the development of sustainable technologies and services in line with meeting its net-zero carbon goal.
One early-stage company the company has invested in is Brimstone, a startup developing the first carbon negative process for cement manufacturing, which starts with carbon-free calcium silicate rock instead of limestone. Another new AWS investment is in Electra, a company that produces iron at lower temperatures using low-grade iron ores and renewable energy. AWS said it intends to use such innovative materials "when they become technically viable and commercially available," and will maintain its ongoing investment to support their development.
With embodied carbon (i.e. the emissions released during building materials’ life cycle, from extraction to manufacturing, transport, and construction to disposal) accounting for around 11% of global carbon emissions per data from the World Green Building Council, AWS admitted that the global construction industry is one of the largest and most difficult sectors to decarbonize.
The company affirmed it is working with iMasons Climate Accord, its members, and the broader industry to help expand the immediate availability of lower-carbon concrete for other companies constructing data centers worldwide.
The AWS statement further affirmed, "As part of The Climate Pledge, Amazon and Amazon Web Services (AWS) are focused on increasing energy efficiency, expanding the use of renewable energy, and reducing the embodied carbon of our infrastructure to reach net-zero carbon by 2040."