Concrete: The Quiet Greenhouse Gas Emitter Beneath Your Feet

Concrete: The Quiet Greenhouse Gas Emitter Beneath Your Feet

When you think of polluting industries, you probably imagine extractive fuel endeavors like coal or oil, and maybe wag a finger towards the garment industry or the ubiquitous use of plastics, also a product of the oil industry. However, there are other, silent industries with less public exposure damaging the planet at alarming rates. Concrete is the most widely used man-made material in existence, and it’s also the source of eight percent of global carbon dioxide emissions. This, the second-most consumed resource behind only water, contributes more CO2 than aviation fuel yearly (2.5% of CO2 emissions) and isn’t far behind the global agriculture industry (12% of emissions). 

Cement, the primary component of concrete, is the source of most of its emissions. Concrete is simply a mix of  water, sand, gravel, and a cement binder. In 2017, global cement production generated approximately 2.2 billion tons of CO2, and more than half of that comes from the calcination process used to create it. 

According to the Yale School of Forestry and Environmental Studies, “[The cement industry is] ranked with CO2 emissions from individual countries, the cement industry would be the third-highest emitter after China and the United States.

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Concrete built our industrialized world. From brutalist parking garages to the Sydney Opera House, concrete tells the story of the 20th and 21st centuries and its aspirations to build bigger, taller, grander structures. While building with alternatives are possible, they’re expensive and may not meet the same sturdiness or resilience standards needed in construction. Developers fall back on the known quantity of concrete, which has decades of use and tests behind it. One can hardly blame an architect for relying on a material that they’re familiar with when constructing a building that could kill thousands if it collapses. Convenient as it may be, concrete with its cement component greatly outpaces the production of plastic, yet enjoys very little criticism from the public. 

All images via Unsplash.

China produces over 4,000 million tons of cement each year, more than twice as much as the second highest pouring country, India, which produces approximately 2,000 tons per year. According to the United States Geological Survey, since 2003, China produced more cement every three years than the U.S. had in the entire 20th century. This is primarily driven by rapid modernization both in China and by China in the Global South, particularly in Southeast Asia and Sub-Saharan Africa. 

Why does concrete emit so much C02? The process to make “clinker,” the primary ingredient in cement, emits a remarkable amount of  carbon dioxide, a known greenhouse gas. In this process, limestone, clay, and other raw materials are ground and mixed with other components like iron ore or ash, then fed into a large cylindrical kiln and headed to approximately 2,640 degrees Fahrenheit (or 1,450 degrees Celsius). This produces both small nodules of sintered limestone mixture and as much as 90% of the cement industry’s greenhouse emissions.

The rapid development of Southeast Asia and Sub-Saharan Africa, driven in part by Chinese investment, population growth, and globalized supply chains, also strains local economies and environments. A black market for sand, an integral part of concrete production, erupted in Southeast Asia in response to population and infrastructure growth. Southern Cambodia is being rapidly developed, and once peaceful towns and riverbeds are being dredged for sand. Most of the profit seems to have remained in the black market, while government officials ignore calls from activists to regulate the extraction for environmental and social concerns. It’s a corrupt system; a 2016 investigation revealed that Singapore reported to have received $752 million from Cambodia, which only reported having exported $5.5 million. 

In China, they are developing new structures at such a rate that malls, towns, and stadiums, all fairly new, sit unused. For instance, the Olympic Bird’s Nest stadium remains empty most days and the National Bureau of Statistics found 450 sq km of unsold rental space across the country. They also export their appetite for construction through the government’s Belt and Road Initiative, an international infrastructure investment project that will splatter roads, dams, and other cement-dependent projects across Africa, Asia, and the Middle East. 

Concrete - The Quiet Greenhouse Gas Emitter Beneath Your Feet..
Dubai in the United Arab Emirates is a concrete marvel.

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In addition to its production, extant concrete structures cause further environmental destruction thanks to its resilience against forces of nature. Flooding in New Orleans and Houston after hurricanes Katrina and Harvey were made more severe because of nonporous concrete roads that could not absorb water. Current infrastructure is inadequately prepared for future flooding and extreme weather caused by global warming. Roads now pave what used to be forests and fields, and entire ecosystems are imbalanced by the inclusion of manmade structures. 

The concrete industry needs to radically change how it creates concrete if it wishes to remain a viable building material as the world grapples with climate change. The industry is attempting to do so through the Global Cement and Concrete Association (GCCA), which was founded in January 2018 partially in response to criticism of the industry, whose members must adhere to its sustainability guidelines. Its Sustainability Charter, published in November 2018, states that “Full Members must commit to attaining full compliance with the Charter within five years (subject to local legal restrictions),” and that members must “Set targets for the five pillars of the GCCA Sustainability Charter, publish company level sustainability performance, report standardised plant level sustainability data to the GCCA through an external service provider, and encourage the implementation of the pillars of the Charter across the value chain.”

This is a good start, but their website also reads like an extended advertisement lauding the benefits of concrete rather than prove the industry is changing as rapidly as it needs to. According to their website, the GCCA believes concrete is inherently sustainable, stating “Concrete is widely used because it is local, available, cost effective (cheap), inert, durable, versatile in mix, form and finish and has excellent in-use performance across many parameters. All of these contribute to concrete’s sustainability value.” However, this does not mention CO2 emissions. It may be cheap, durable, and inert, but that says nothing of its contribution to climate change and the myriad crises (displacement, loss of habitat, extreme weather, air quality, etc) that will befall the earth because of it. 

Concrete - The Quiet Greenhouse Gas Emitter Beneath Your Feet

Some of the GCCA’s sustainability standards are incredibly vague and don’t provide quantifiable objectives for its members. For instance, one point under the pillar of ‘Health & Safety’ reads “Promote the sharing of good health practices,” and another under ‘Social Responsibility’ suggests members “establish a systematic dialogue process with stakeholders.” These sound positive and would fit well into a press release, but allow companies wiggle room to do the bare minimum . 

Emissions could be reduced merely by changing the way the industry and global governments approach development. Considering the entire lifecycle of a structure and building for longevity rather than cost or speed would necessarily reduce the amount of concrete created. Using cement more efficiently, minimizing wasteful development, and optimizing the application of cement in new buildings could all mitigate the problem with relative ease compared to institutional regulatory changes. The business world is also reacting to the need for green materials; startups like the North Carolina-based bioMASON are making cement from renewable resources like bacteria that require significantly less heat and emit very little carbon dioxide.

Since startups move slowly and the current industry even slower, it will take government intervention to adequately curb cement production. Like industries related to dirty industries like coal, the people employed by the cement and concrete industries must be given an opportunity to shift into greener work. According to the Guardian, the construction sector in China “employs more than 55 million workers – almost the entire population of the UK.” That’s no reason to not make changes, but an opportunity to change an entrenched system into one that fits into the ethos of the 21st century and its changing values from bigger, often wasteful development to one that prioritizes reuse, salvaged materials, and respect for the local and global environment. 

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