The Inconspicuous Climate Guzzlers Under our Feet, Over our Heads, and on All Sides

Today’s Gup Shup is challenging. I have six key messages. Each could take up a full-semester college course. But we have only a few paragraphs for each message… so, let me jump right in, then, with terminology and a few concepts. We will tackle just three of the six today, by setting up the issues and appreciating the task at hand. Next time we will see what is being done about it, what else needs to be done, and how we may be able to lend a voice.

Message 1: Business as Usual in the Building Industry is Killing Our Planet. Let’s consider the “built environment,” which is the antithesis of the natural environment. Wherever humans put up structures, roads, highways, flyovers, houses, office towers, river embankments, paved areas, pedestrian zones, whatever looks like development and progress and improving the standard of living—that’s the built environment. 

How does the built environment contribute to climate change? What can be done about something that all of us take for granted in our lives, so much so that we barely notice it? Who knew that our roads and houses and skyscrapers and sidewalks were all actually “climate villains”? That we urgently need 2.0 versions of them, and of the materials we use to build them? Most of this Gup Shup looks at buildings, but it applies to all concrete structures.

I just need to say one thing on buildings before we get started on today’s topic, so I can make it clear how today’s topic is DIFFERENT: Buildings themselves are not new to the climate change conversation. This is because many energy professionals have been sounding alarms for a decade about the need to increase ENERGY EFFICIENCY for buildings. They correctly spotted the “buildings sector” as a huge, dumb energy “waster.” They continue to sensitize policymakers to promote mandatory energy efficiency standards for “green buildings.” There are relatively simple building insulation measures to avoid energy leaking out from the inside in the form of heated or cooled air, or to prevent extra heat/cold seeping in from the atmosphere outside, that makes us turn up our air-conditioners or heaters, resulting in higher energy bills. In fact, as part of the proposed US legislation on Green Jobs and the Climate, increasing energy efficiency through grants and loans for retrofitting buildings––which creates green jobs––features prominently in reducing emissions by targeted dates. An energy efficient building reduces energy waste and therefore uses less electricity. Thus, fewer carbon emissions and more progress towards the climate target. 

Some building owners, particularly in Europe, are even pursuing “passive” or “net zero” buildings. These structures use techniques such as motion detectors for occupancy and deploy auto-shut off technologies to minimize energy consumption on lighting and cooling/heating of unoccupied spaces. They also generate as much clean energy from solar panels on their rooftops and building facades as the inside occupants consume. So, they don’t even need to “import” electricity from a fossil-fuel power plant. This is great, but energy efficiency in buildings is NOT our subject for today, even though we are talking about buildings. Halting the wastage of energy is of course a must-do. But what about the building itself? What about the carbon footprint of the structure, never mind the energy consumption of the occupants?  Let’s go back to those basics! 

First, we have to understand why most of our existing buildings have been harmful to the climate (by guzzling energy and excavating and destroying vulnerable landscape features). Then we can appreciate why the proposed “2.0” solutions are not yet gaining traction. Future buildings must let us and our kids still live comfortably, but without totally destroying the only planet we have. 

Message 2: Cement. Look out of the window and you are likely to see an ocean of concrete from top to bottom, that probably looks solid, familiar, safe and comforting to you. To understand concrete properly, let’s first look at cement which is the key ingredient in concrete. Cement is the glue that holds concrete together. The technical term is Portland cement (that’s not a brand name or place name, any more than sterling silver or stainless steel; it’s just a designation). It is the grey powdery stuff that comes in 50kg bags, that is mixed with water at construction sites. But in that unremarkable-looking bag of grey powder lies the “mother of all carbon footprints!”

Globally, the cement industry dumps nearly 3 billion tons of CO2 into the air EACH YEAR, about three times that of the aviation sector. That CO2 comes from two sources in the cement-making process. First, you need to heat a cement kiln to about 1500 degrees Celsius; burning coal is the most common method, and 40% of the total CO2 burden of cement comes from this heating (or “cooking” process); when coal is burned, CO2 is released. Then you also have a chemical reaction going on inside the cement kiln, that is “designed to release CO2”, accounting for the other 60% or more of the carbon footprint.

Crushed limestone and clay and a few other substances are heated to make “clinker” which is then mixed with gypsum and ground into a fine grey powder that we call Portland cement. Alas, the largest part of the CO2 burden comes from the chemical reaction (thermal decomposition) that occurs when you heat the crushed limestone,to break it down into lime and carbon dioxide to make clinker. The carbon trapped in the limestone is released, combines with oxygen in the air and escapes as CO2. This carbon dioxide accounts for 60-70% of cement’s CO2 footprint. 

So, if you were to substitute a perfectly clean source of energy (instead of coal) to heat your kiln to 1500 C, you would surely reduce the carbon footprint. However, you would still be confronted with the CO2 emission from the breakdown of limestone (calcium carbonate) that is essential to the formation of cement. This is why cement is considered one of the “hard to abate” industries. Clean energy alone, to get rid of the coal-burning part with the cement kiln will help, but not totally. 

Cement is one of the global economy’s most carbon-polluting industries. Responsible for about 8 percent of global carbon dioxide (CO2) emissions in 2015, if it were ranked with individual countries, the cement industry would be the third-largest greenhouse-gas emitter in the world behind only China and the United States. And this already outsized footprint is only projected to grow in the coming decades as economic development and rapid urbanization continue across Southeast Asia and sub-Saharan Africa.  

... if it were ranked with individual countries, the cement industry would be the third-largest greenhouse-gas emitter in the world behind only China and the United States.

Message 3: Aggregates. Concrete, which incorporates the whole carbon footprint of cement as a key ingredient, also has its own, additional environmental footprint. Concrete is made up of three main ingredients: water, Portland cement, and aggregates (this refers to sand, gravel and crushed stone). Aggregates increase the strength of the concrete beyond what cement can provide on its own. Cement, mixed with water, forms a paste that binds together the aggregates to form a synthetic type of rock that we call concrete. We make our buildings, roads, airport runways, sidewalks, driveways and any number of structures from it. The water to cement ratio (w/c ratio) changes the properties of the final product (concrete), which allows the engineer to design concrete that meets their specific construction needs. For each ton of cement, the building industry needs six to seven tons of sand and gravel.  

How big is this sector? If you divide up all the concrete used globally every year, three tons of concrete would go to every person on the planet (7.8 billion people), making it the second most consumed resource after water! And six to seven tons of sand and gravel for each of those tons of concrete, every year! 

This is truly mind-boggling, because… securing the supply of the aggregates required for the manufacture of concrete, particularly mining sand from riverbeds and coastal areas, is causing irreparable environmental damage to our natural capital. Sand and gravel represent the highest volume of raw material used on earth after water. Their use greatly exceeds natural renewal rates. Moreover, the amount being mined is increasing exponentially year on year, mainly as a result of rapid economic growth in developing countries. China alone manufactures and uses half of the world’s concrete at present. Concrete is an aspirational product. A low-income person sleeping on an earth floor in a wooden shack looks forward to the day when they can have a solid house and a dry, concrete floor to sleep on. Economic prosperity leads to new roads, bridges, highways, buildings… The global demand for concrete will not go down any time soon. In fact, it’s projected to rise by 24% in the coming decade. But under business as usual, it’s consuming our planet, adding CO2 emissions and eating up our natural capital.

In most countries, sand mining and riverbed dredging regulations are often established without scientific understanding of the consequences, and projects are carried out without environmental impact assessments or strict supervision. As a result, aggregate mining has affected the provision, protection and regulation of ecosystem services. Sand mining in rivers, lakes and coastal beaches releases vast dust plumes and changes water turbidity (the quantity of dissolved solids), making the water cloudy and disrupting the feeding and breeding grounds for fish and other animal life). It has severely negative impacts on water quality, the pH or acidity of the water, and therefore the flora and fauna that can survive in the water. Water levels change, and floods and droughts are artificially triggered when riverbeds are hollowed out. The biggest change occurs in the level of silt that is transported through the water as part of the natural cycle. Putting up dams for hydropower plants is another activity that is harmful to the transport of sediments. In fact, some academics note: “Damming and mining have reduced sediment delivery from rivers to many coastal areas, leading to accelerated beach erosion. Onshore sand mining in coastal dune systems such as those in Monterey Bay, California, in the United States, can also lead to long-term erosion, in this instance, 0.5 to 1.5 metres a year…” (Kondolf, 1997).

A recent publication by UNEP notes that globally, between 47 and 59 billion tonnes of diverse material (iron ore, bauxite, gold, coal, cobalt etc) is mined every year on our planet of which sand and gravel account for both the largest share (from 68 per cent to 85 per cent) and the fastest extraction increase. Yet the absence of reliable global data contributes to the lack of awareness on this issue. 

One obvious reaction to this troubling information is, “wait—why are they using sand from ecologically fragile riverbeds, when there is abundant sand in the desert?” Why not take sand from the desert where the environmental impact is lower, and use that as part of the aggregates needed to make concrete? The sad answer is that desert sand grains are too fine and well rounded, due to centuries of wind erosion, and they do not bind as well to give the properties of high-quality concrete that come from sharp jagged edges on submerged sand grains pulled out of riverbeds and beaches. This is what the experts say in an academic paper on the subject: “River and marine aggregates remain the main sources for building and land reclamation. For concrete, in-stream gravel requires less processing and produces high-quality material (Kondolf, 1997), while marine aggregate needs to be thoroughly washed to remove salt.” If the sodium is not removed from marine aggregate, a structure built with it might collapse after few decades due to corrosion of its metal structures (Delestrac, 2013). Most sand from deserts cannot be used for concrete and land reclaiming, as the wind erosion process forms round grains that do not bind well (Zhang et al., 2006).

So, we have looked at the carbon footprint of cement and the environmental footprint of concrete, and we realize that the global use of concrete is set to grow by 25% in the next decade, to support rapid urbanization mainly in developing countries, to catch up to the living standards of rich countries. 

Here, in a nutshell, is another expert opinion on why we MUST change our mind-set with respect to buildings and the construction industry:

“The building industry takes a staggering toll on the environment. It’s not just concrete, which is depleting the world’s sand, making cities more flood prone, and spewing a huge amount of greenhouse gases into the atmosphere along the way. There’s also the insulation in our walls, the vinyl coating our floors, and the laminates in our countertops, most of which are derived from fossil fuels and have a sizable carbon footprint. From the foundations to the roof, today’s buildings are part and parcel of our extractive economy.  And that’s just the construction. Factor in the energy used to power and heat them, and buildings are responsible for nearly 40 percent of global carbon emissions, according to the U.N.” 

Next time we will dive into what the proposed solutions look like, and how much urgency is being felt to pursue those solutions. This is truly an example of where an existential change is needed in order to change course from our current path. We have managed to make major lifestyle changes before on things that were once unthinkable, like celebrating women’s voting rights (!), wearing seatbelts, stepping outside the office building for a cigarette, not smoking inside an aircraft, respecting speed limits and traffic regulations, and any number of other behaviours that were once normal but now look strange. All of us need to internalize and feel concern over the planetary damage that’s being done from our massive consumption levels of “cement and concrete 1.0.”  We need to move to the 2.0 version as soon as possible and start to see today’s materials as unacceptable in terms of the damage they are doing to our kids’ future on this planet. Hopefully we will feel better once we hear those certain solutions are beginning to emerge, and we can do our bit by pushing vigorously for them to go mainstream. Stay tuned!

Till next time, Mohua

Photos by Vivint Solar, Rodolfo Quirós, Yury Kim, and Aleksandar Pasaric from Pexels.