At every step of the process, cement manufacturing has an impact on the environment. These include limestone quarries, which are visible from great distances and may permanently alter the local environment, emissions of airborne pollutants in the form of dust and gases; noise and vibration when operating machinery; and blasting in quarries.
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Environmental Impacts of Cement Production
Between 4 and 8% of the world’s total CO2 emissions come from concrete, which has a complicated environmental impact that is influenced by its manufacture, applications, and direct effects on infrastructure and buildings. Cement, which has its own environmental and social effects in addition to substantially influencing those of concrete, is a significant component.
1. Emissions of Carbon Dioxide and Climate Change
With up to 5% of all CO2 emissions produced by humans occurring in the cement business, 50% of which come from chemical reactions and 40% from fuel combustion, it is one of the two greatest producers of gas in the world that lead to climate change.
The estimated CO2 output for the production of structural concrete (with about 14% cement) is 410 kg/m3 (or approximately 180 kg/tonne at a density of 2.3 g/cm3); this output is decreased to 290 kg/m3 when 30% fly ash is used in place of cement.
For every ton of cement produced, 900 kg of CO2 is released into the atmosphere, making up 88% of the emissions related to an average concrete mix. The CO2 emission from the manufacture of concrete is directly proportional to the cement content utilized in the concrete mix.
When calcium carbonate is thermally destroyed, producing lime and carbon dioxide, the production of cement results in greenhouse gas emissions. Energy use during cement production also contributes to this problem, especially when fossil fuels are burned.
The fact that concrete has a very low embodied energy per unit mass is one aspect of the concrete life cycle that deserves attention. This is mostly due to the availability and frequent accessibility of the components used in concrete production, such as water, pozzolans, and aggregates, in local resources.
Accordingly, cement manufacturing uses 70% of the embodied energy in concrete, whereas transportation uses only 7%.
Concrete has a lower embodied energy per unit mass than the majority of other building materials, aside from wood, with a total embodied energy of 1.69 GJ/tonne. Due to the enormous mass of concrete structures, this comparison is not always immediately applicable to decision-making.
It is important to remember that this estimate is based on concrete mix proportions with no more than 20% fly ash. According to estimates, replacing one percent of cement with fly ash results in a 0.7% decrease in energy usage. This would result in sizable energy savings because some proposed mixes contain as much as 80% fly ash.
According to a Boston Consulting Group report from 2022, investments in creating more environmentally friendly cement result in greater greenhouse gas savings than investments in electricity and aviation.
2. Surface Runoff
Flooding and severe soil erosion can result from surface runoff, which occurs when water runs off impervious surfaces like non-porous concrete. Gasoline, motor oil, heavy metals, waste, and other pollutants frequently end up in urban runoff from sidewalks, roads, and parking lots.
Without attenuation, a typical metropolitan area’s impermeable cover reduces groundwater percolation and results in five times as much runoff as a typical woodland of the same size.
Many recent paving projects have started using pervious concrete, which offers some level of automatic stormwater management, in an effort to counterbalance the detrimental consequences of impervious concrete.
Concrete is carefully laid with carefully calculated aggregate proportions to produce pervious concrete, which permits surface runoff to seep through and return to the groundwater.
Both flooding and groundwater replenishment is facilitated by this. Pervious concrete and other discretely surfaced areas can act as an automatic water filter by blocking the passage of some dangerous pollutants like oils and other chemicals if they are appropriately built and coated.
Sadly, there are still drawbacks to using pervious concrete on a broad scale. Its lower strength compared to conventional concrete restricts use to low-load areas, and it needs to be installed carefully to minimize susceptibility to freeze-thaw damage and silt buildup.
3. Urban Heat
What is known as the urban heat island effect is mostly caused by concrete and asphalt. The world is expected to add 230 billion m2 (2.5 trillion ft2) of buildings by 2060, which is an area equivalent to the existing global building stock.
According to the United Nations Department of Economic and Social Affairs, 68% of the world’s population is forecast to live in urban areas by 2050. As a result of the additional energy they use and the air pollution they produce, paved surfaces pose a serious threat.
A region has a lot of opportunities for energy savings. The demand for air conditioning should ideally decline as temperatures drop, conserving energy.
However, studies on how reflecting pavements affect surrounding structures have indicated that absent reflective glass on the buildings, solar radiation reflected off the pavement can raise building temperatures, increasing the need for air conditioning.
Moreover, local temperatures and air quality can be impacted by heat transfer from pavements, which cover cities. Using materials that absorb less solar energy, such as high-albedo pavements, can restrict the flow of heat into the urban environment and regulate the UHIE. Hot surfaces warm the city air through convection.
For surfaces made of pavement materials now in use, albedos range from around 0.05 to roughly 0.35. Pavement materials with high beginning albedo tend to lose reflectivity over the course of a typical life service, whereas those with low initial albedo may gain reflection.
Thermal comfort effect and the necessity for additional mitigation measures that don’t endanger pedestrian health and safety, particularly during heat waves, are additional factors to take into account. The “Mediterranean Outdoor Comfort Index” (MOCI) is calculated while
People are exposed to weather and thermal comfort conditions, therefore overall urban designs should still be taken into consideration when making judgments. When combined properly with other technologies and techniques like vegetation, reflective materials, etc., the usage of high albedo materials in urban settings can have beneficial effects.
4. Concrete Dust
During earthquakes and other natural calamities, as well as during building destruction, a lot of concrete dust is frequently released into the atmosphere. Following the Great Hanshin earthquake, it was determined that the main cause of severe air pollution was concrete dust.
5. Radioactive and Toxic Pollution
Health issues may arise from the inclusion of some compounds in concrete, including both desired and undesirable additives. Depending on the source of the raw materials used, different concentrations of naturally occurring radioactive elements (K, U, Th, and Rn) may be found in concrete structures.
For instance, some stones naturally emit Radon, and the waste from old mines used to contain a lot of Uranium. Inadvertently using toxic compounds as a result of contamination from a nuclear accident is another possibility. Depending on what had been included in the concrete before demolition or cracking, dust from debris or fractured concrete may pose major health risks.
However, it’s not necessarily risky and could even be advantageous to embed toxic substances in concrete. In some instances, adding certain compounds, including metals, to cement during the hydration process immobilizes them in a safe condition and inhibits their release into the environment.
6. Nitrogen Oxide (NOx)
Nitrogen oxide (NOx) has a number of negative effects on human health and the environment, including ground-level ozone, acid rain, global warming, deteriorating water quality, and vision impairment. Children and persons with lung problems like asthma are among the affected groups, and exposure to these conditions can harm lung tissue in people who work or exercise outside.
7. Sulfur Dioxide (SO2)
High levels of sulfur dioxide (SO2) can impair breathing and exacerbate respiratory and cardiovascular conditions that are already present. Asthmatics, people with bronchitis or emphysema, kids, and the elderly are among sensitive populations. The main cause of acid rain, or acid deposition, is SO2.
8. Carbon Monoxide (CO)
By decreasing the amount of oxygen delivered to the body’s organs and tissues, carbon monoxide (CO) can have a detrimental impact on one’s health. It can also have negative effects on the cardiovascular and nervous systems. Smog, or ground-level ozone, which can lead to respiratory issues, is created in part by CO.
9. Fuels and Raw Materials
Depending on the inputs and the procedure, a cement mill uses 3-6GJ of fuel to make a tonne of clinker. The primary fuels used by the majority of cement kilns today are coal, petroleum coke, and, to a lesser extent, natural gas and fuel oil.
If they meet rigorous criteria, certain waste and byproducts with recoverable calorific value can be utilized as fuels in cement kilns to replace some of the traditional fossil fuels, such as coal.
In places of raw materials like clay, shale, and limestone, certain waste and byproducts containing beneficial minerals like calcium, silica, alumina, and iron can be used as raw materials in the kiln.
The line between alternative fuels and raw materials is not always clear because certain materials have both valuable mineral content and recoverable calorific value.
For instance, sewage sludge burns to produce ash-containing minerals that are beneficial in the clinker matrix despite having a low but significant calorific value.
Environmental Impacts of Cement Production – FAQs
What pollution do cement industries cause?
Cement industries majorly cause air pollution.
How much CO2 is produced by cement production?
The amount of CO2 that is produced by cement production is about 0.9 pounds for every pound of cement.
How does cement production cause climate change?
This is how cement production causes climate change. When calcium carbonate is thermally destroyed, producing lime and carbon dioxide, the production of cement results in greenhouse gas emissions which in turn causes climate change.
What are the environmental impacts of concrete?
Concrete gotten from cement production is one of the major generators of carbon dioxide, a potent greenhouse gas. The topsoil, which is the earth’s most fertile layer, is adversely affected by concrete. Hard surfaces made of concrete contribute to surface runoff, which can lead to soil erosion, water pollution, and flooding.
From what we have seen in this article, we have known that though cement production is a necessary ingredient in driving the development of society, they are harmful to our environment. This calls for major advancement away from cement to other sustainable and environmentally friendly alternatives to building construction.
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A passion-driven environmentalist by heart. Lead content writer at EnvironmentGo.
I strive to educate the public about the environment and its problems.
It has always been about nature, we ought to protect not destroy.