Green infrastructure and sustainable building materials
Published Aug 03 2021 04:10 PM 8,845 Views



The Green Imperative for Construction


From the mountains of California to the Gulf Coast of Florida, the early part of my professional career was spent practicing geotechnical engineering and as a research hydrogeologist. In these roles, I focused on engineering hillside mitigation efforts and working on municipal water production and wastewater treatment projects. While working with small and local governments in coastal Florida, our challenge was to secure potable water while managing ‘reclaimed’ water for irrigation or subsurface storage (ASR), as well as handling wastewater for subsequent treatment. The construction projects I was involved in were aimed at sustainable use of water within the context of supplying a necessary resource to a large metropolitan population. In a very real sense, the intersection of sustainability and construction is something I remain extremely passionate about. By extension, given that construction projects are significant consumers of goods produced from raw materials, green infrastructure for construction remains one of the most critical investment areas for the world.


Shifting our concern from civil engineering and water-resource management to emissions, it is with extreme humility that I share our current predicament: it is estimated that manufacturing and construction contribute about 31% of the 51 billion tons of greenhouse-active gases to our atmosphere annually. Moreover, this may be a best-case scenario. Consider, for example, that despite being the wealthiest country in the world, the United States of America ranks 13th when it comes to the overall quality of its infrastructure. Consequently, identified as an early priority by the Biden Administration, is a major rebuilding of infrastructure across the country. While the most-developed nations add to the demand for construction, they are contributing to an existing demand fueled by a rapidly developing appetite across the planet. Netted out, the emissions attributed to construction are already significant and seemingly under pressure to increase. The need for sustainable construction has never been more pressing.


In refreshing contrast to infrastructure investments made in the past, the Biden Administration’s plan “…prioritizes addressing long-standing and persistent racial injustice. The plan targets 40% of the benefits of climate and clean infrastructure investments to disadvantaged communities.” Thus, the situation in the United States presents as a microcosm of what exists globally: to service communities with highly disparate infrastructure needs, green construction will demand significant innovation.


It takes electricity to make and build things. To place the focus squarely on the construction sector here, however, we will assume ubiquitous and equitable availability of electricity. To appreciate the precarious nature of our ‘codependent relationship’ with Carbon in the construction context, we will consider a few examples here.


Manufactured Carbon Dioxide


Our urban centers are often described as concrete jungles. As existing centers sprawl and new ones are poured into existence across the planet, it appears our appetite for this essential construction material is unlikely to be curbed. In and of itself, concrete does not pose an emissions concern. Calcium-based cement, a major ingredient of concrete, is not an emissions concern either. But Calcium needs to be ‘extricated’ from carbonate rocks, like limestone, by heating. And during heating, Carbon Dioxide is released.




Figure 1 A calcinator is an industrial oven that extracts quicklime (Calcium Oxide, CaO) from limestone (Calcium Carbonate, CaCO3) by heating it. The Calcium needed for cement is derived from quicklime. Carbon Dioxide (CO2) is released in the process.


This is representative of the challenge confronting the construction sector as a whole. On many levels, it makes sense to acquire the Calcium needed for concrete cement from limestone; there is no alternative. Innovation needs to place emphasis on reimagining the industrial processes involved. Easy enough to state, the Carbon Dioxide produced in the calcination process needs to be captured – all of it, without leaking or venting. Then, the captured CO2 needs to be sequestered.


Although the details differ, industrial processes involved in producing steel and plastics suffer similar complications. Carbon Dioxide is released during those manufacturing processes as well. In addition, concrete, steel, and plastics production are not the only examples of industrial processes in which greenhouse-active gases are released.


Towards a Concrete Solution


Traditional calcinators leak CO2. Retrofitting or replacing equipment to ensure all the CO2 released during the calcination process is captured, is accompanied by a cost. In other words, there exists a “green premium” associated with Calcium, cement, and ultimately, concrete production. Even though the price per ton for cement is about USD 124, the green premium roughly doubles this price, to account for capturing and handling the Carbon Dioxide produced during cement production.


Almost remarkably in the case of concrete, the problem is at least part of the solution. For example, the CO2 captured during calcination can be subsequently used to ‘carbonate’ concrete. When strategically introduced into wet concrete, the CO2 combines again with Calcium and is stably sequestered (as the solid CaCO3). Because the solution directly aligns with its sustainability goals, Microsoft has invested in a cleantech company that literally sequesters CO2 in the mix.


Although the ability to sequester CO2 in wet concrete is likely to improve, it is clear that innovation needs to proceed along multiple fronts in parallel.


Concrete Alternatives?


Whereas the best we can hope for is to effectively manage the CO2 that is inevitably released during calcination, other industrial processes can be used to re-imagine construction. Consider cross-laminated timber (CLT) for example. As an engineered wood, CLT has a number of appealing properties, for example, strength, lightness, usage flexibility, prefabrication potential, and thermal insulation. It can even be fabricated from lower grades of wood. Thus, in addition to being of value in places where wood might not have been traditionally employed (even in lieu of concrete), CLT is a sustainable material as wood is a renewable resource that has already captured and sequestered some CO2. In making an explicit choice for CLT in its new Silicon Valley Campus, Microsoft has demonstrated with clarity that sustainability and sound business practices can be aligned. In fact, by making use of some 2,400 tons of CLT, the new Microsoft campus is on track to become the largest wood structure in the US (in terms of volume used). The use of CLT at its Silicon Valley Campus is an example of a broader Microsoft imperative with respect to construction and sustainability in general. When it comes to CLT, what proves to be successful for the high-tech Valley may also prove to be successful for developing regions. In such regions, for example, it may only be practical to harvest a lower-quality of wood, perhaps due to accessibility, availability, proximity, and/or lack of sophisticated and expensive logging equipment. In these areas, the infrastructure required to fabricate and distribute CLT may be easier to establish than that for concrete.



Figure 2 CO2 emissions for the building sector projected out through 2050. Because materials exceed operations, there exists a compelling need to address the challenge of embodied Carbon. (Source: BuildingGreen Spotlight Report, 2018.)


The Embodied-Carbon Imperative


The embodied-Carbon imperative aims to take choices such as CLT versus concrete to the next level. The impetus for the imperative in the case of construction is clear and pressing: embodied Carbon is poised to exceed operational Carbon from an emissions perspective. Embodied Carbon derives from anything not involved with energy consumption, like a building or infrastructure since those emissions are associated with construction materials and processes. Taking a lifecycle perspective, embodied Carbon originates when infrastructure is first built, while it is operated (except for the operational Carbon of energy consumption), and even when it is decommissioned.


To make the holistic requirements for embodied Carbon tangible, Microsoft teamed with construction giant Skanska to develop the Embodied Carbon in Construction Calculator (EC3). Subsequently embraced by numerous partners that collectively represent stakeholders across the construction industry, EC3 quantifies choices such as CLT versus carbonated concrete in a highly tangible way. Microsoft, for example, has made use of EC3 in a 17-building redevelopment project on its main campus in Redmond, Washington. By making use of EC3, Microsoft expects to shave some 30% off its Carbon footprint for this project by reducing the amount of embodied Carbon.


Ironically, the focus is increasingly shifting towards embodied Carbon owing to ongoing, and systematic gains in reducing operational Carbon. The most advanced example of energy efficiency speaks to reducing operational Carbon by making use of breakthrough technologies such as Digital Twins. In a business-as-usual projection from Architecture 2030, for example, embodied and operational Carbon would contribute equally to emissions through 2050. Given the demands for infrastructural investments within the US and abroad, the need to confront embodied Carbon is compelling. When considered within the context of the Paris Agreement, the role of construction is a major contributor to what is, without exaggeration, a climate emergency.

Innovation for the Future


To reiterate, it is estimated that manufacturing and construction contribute about 31% of the 51 billion tons of greenhouse-active gase.... Because manufacturing and construction make significant use of electricity, these industries indirectly contribute to any emissions generated by the production of electricity. Net-zero solutions for construction are required to account for embodied Carbon. Consequently, there is a need to be extremely innovative and vigilant in how we implement industrial processes in manufacturing construction materials, as well as how we operate our factories and buildings over their entire lifecycle. Inevitably, as we collectively grapple with the implementation of our path forward towards a net-zero future, our focus will need to become increasingly holistic – from isolated factories and buildings to integrated campuses, and ultimately, urban centers. According to UN projections, about 68% of the world’s population will live in cities by 2050, which is regarded by some as a conservative estimate. Moreover, to address long-standing injustices that prevail in marginalized populations, innovation will be required to ensure that sustainable construction can be applied successfully in a variety of settings.


As a professional at an early stage in my career, I enjoyed contributing to the management of water as a precious resource in construction projects. In many cases, I was able to leverage my background as a hydrogeologist in tandem with innovative technology, such as reverse osmosis, to deliver sustainable solutions like purified water. Sustainable construction also needs an infusion of innovative solutions to ensure a net-zero future. As the situation in the US makes clear, different communities are at different stages and are therefore in need of different solutions. By making sustainable construction in disadvantaged communities a point of investment, I remain hopeful that disparities within the US will ultimately be reduced. Innovation-fueled action will be good for all communities and good for the planet.


To learn more about Microsoft’s efforts to reduce embodied Carbon in its construction projects please consult the white paper identified here. For an even broader perspective on Microsoft’s efforts and progress to date with respect to sustainability, please consult the 2020 report here.


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