In this article we will answer the question, “Why Cement is bad for the environment?”. The discussion will include the greenhouse gases emitted of the cement industry, damage of limestone extraction, and the effect of using concrete in the cities. In addition, this article will present a brief discussion of eco-friendly cement alternatives.
Why is cement bad for the environment?
Cement is bad for the environment because it emits carbon dioxide (CO2) emission and other greenhouse gases, posing harm to air quality in earth’s atmosphere. Concrete alters the pre-existing ecosystem leading to loss of fertile soil and loss of biodiversity. The cement industry is also responsible for noise pollution and ground vibration affecting the land stability causing soil erosion.
Air pollution is a major environmental challenge during raw materials processing for cement manufacturing. The kiln operation which is the production of clinker requires heat to transform limestones (calcium carbonate) into lime (calcium oxide) through the reaction called calcination, producing CO2 with water vapor. Clinker is a solid lumps or nodules used as intermediary products to produce cement. This clinker production is the major contributor to CO2 emission and other greenhouse gases of the cement industry.
Greenhouse gases released by cement industry
These greenhouse gases increasing concentration in the atmosphere are the major contributors to climate change by trapping the heat affecting the planet’s weather and climate systems. This shift in the climate does not only change the planet’s average temperature to rise or what is referred to as global warming but also causes extreme weather events, shifting the wildlife population and habitats, rising seas, and other wide range of environmental impacts.
Here are the common greenhouse gases produced and released to the atmosphere and their environmental impacts.
· Carbon dioxide (CO2)
The global cement industry carbon footprint is large generating 2.2 billion tons of CO2, contributing to 8% of the total global CO2 emission making it the third-highest CO2 emitter when ranked with countries with highest CO2 emission, ranked after China and the United States.
CO2 is the major contributor to global warming trapping the heat in earth’s atmosphere.
· Nitrogen oxides (NOx) and Sulfur oxides (SOx)
In China alone the industry releases 4% of SO2 and 10% of NOx into the atmosphere annually. Various studies cited that for every 1380 million tons of CO2 emitted, 410, 1.3 and 2.27 million tons of PM, SO2 and NOx were also released.
Sulfur oxides and nitrogen oxides also contribute to acid rain. These pollutants released from cement factories to the atmosphere react with water, oxygen, and other chemicals to produce acids. This acidity or rain can pose harmful effects to plants, soil, aquatic animals, freshwater systems, and infrastructures.
· Particulate matters (PM)
Particulate matters generated from the cement industry usually come from dust formation during Portland cement production. During storage in cement plants, low moisture content of raw materials, clinker, and cement and with the influence of wind, dusts are diffused and carried to the atmosphere contributing as particulate matter [5].
Accumulated PM affects the vegetation nearby, causing loss of plant tissue, reducing photosynthetic activity, reducing the crop yields by burying the seedlings, and increasing soil erosion. This will also affect marine organisms, accumulation of dust in the bodies of water nearby can decrease the oxygen level, killing or displacing fish, crabs, and many other marine organisms.
Damage of limestone extraction for cement manufacturing
Concrete is typically made up of 41% crushed rock, 26% sand, 16% water, 11% Portland cement, and 6% entrained air. Portland cement is made from calcium carbonate, silicon, aluminum, iron. About 1.6 tons of these raw materials are required to make 1 ton of cement [2]. Major raw materials required for cement processing are quarried in case of hard rocks such as limestone with the aid of blasting when necessary while softer rocks such as clay can be dug directly by excavators.
Quarrying and excavation to obtain limestone have the following impacts:
· Irreversible damage to the source limestone like mountains
· Depletion of groundwater in the extraction site
· Damage the most fertile layer of the earth
· Degradation of forests
· Deterioration of land and aquatic biodiversity
· Changes the hydrogeological and hydrological regimes
Also, extraction and raw material processing for cement contains heavy metals such as mercury. About 1.17-1.53 tons of mercury were emitted by the process accounting for 10% of mercury released globally [4]. Mercury is highly toxic; thus, intake of this heavy metal is dangerous to human health. Intake at harmful concentration can affect the nervous system in adults. Mercury accumulated concentration had been observed in fish, birds, and other animals being consumed by humans.
What are the effects of concrete in the cities?
Concretes are responsible for heat-island effect and surface run-off in cities. Concrete is the foundation of modern development, strengthening defenses against natural disasters and providing healthcare education, energy, transport, and other industries a structure. With the continued development due to technological advancement construction activities also increase.
Construction industry grew to approximately 12 trillion U.S. dollars before the pandemic and is projected to grow by 3% per annum. This spending data includes cost of labor, materials, architectural and engineering work, and taxes [6]. This growth in the construction industry also dictates the cement global demand affecting not just cement raw material extraction and production grounds but also the use of cement particularly in cities.
Heat-Island Effect
The increase of construction activities worldwide dictated the demand for cement. Together, building and construction are responsible for 39% of all carbon emission in the world. Furthermore, concrete and asphalt for buildings, roads, bridges, and other infrastructure are primary contributors to heat-island effects.
The term heat island refers to areas that are relatively hotter than the surrounding. Concrete pavements increase the local temperature and influences the air quality by absorbing the warmth of the sun and trapping gases from car exhausts and air conditioner units [7]. Heat islands elevate the emission of air pollutants and greenhouse gases forming ground-level ozone and acid rain which is both harmful to health and environment. This ground-level ozone affects sensitive vegetation especially during growing season and ecosystems.
Surface run-off
Buildings and roads can also cause surface runoff, when water runs odd non-porous reinforced concrete flooding and severe soil erosion can occur. These runoffs can also affect the water quality carrying sediments from concretes affecting the turbidity of the nearby body of water.
What are the eco-friendly cement alternatives?
Here are some eco-friendly alternatives for concretes [8]:
· Ashcrete
Ashcrete if the combination of fly ash with lime and water. Fly ash are produced from combustion of coal usually disposed of in landfills. Apart from it lessens the emission of carbon dioxide, benefits of utilizing fly ash includes increased concrete strength and lessen the bleeding and shrinkage unlike traditional cement.
· Concrete debris
Utilizing concrete debris is the best solution to cut down the resource consumption and lessens the processing of the raw material to cement, thus, reducing the carbon emission. Also, it saves landfill space and reduces the use of water resources.
· Blast furnace slag
Blast furnace slag is a glassy granular material which is a byproduct when molten iron slag is quenched into water and steam from the blast furnace. This can be used as a substitute to 70 to 80% of cement, improving the durability of the concrete.
· Bamboo
Bamboo can be used as framing in buildings and can be a substitute to rebar and concrete construction. Although lightweight, bamboo has tensile strength enough to be utilized as an alternative to expensive construction materials.
· Recycled Plastic
Plastic is a non-biodegradable material causing landfill to overfill and releases high concentration of greenhouse gases. Utilizing plastic as concrete reduces the CO2 by half and can eliminate further problems of plastic accumulation in the future.
Conclusion
This article answered the question, “Why is cement bad for the environment?”. It was discussed that a major factor the cement industry affects the environment is due to its high CO2 emission responsible for global warming. Other greenhouse gases released by the industry contributes to climate change.
Raw material extraction and manufacturing of cement endangers the pre-existing ecosystem in extraction and manufacturing sites. The impacts of activities for cement production includes biodiversity loss, degradation of soil, and water pollution. Furthermore, this article provided the impact of concrete as material in cities and cited several eco-friendly cement alternatives.
For any questions and suggestions about this article, please feel free to submit your thoughts in the comment section below.
Frequently Asked Question (FAQs): Why cement is bad for the environment?
Is concrete eco-friendly?
Concrete is not eco-friendly. Raw material extraction, production, consumption, and disposal of cement utilizes high amounts of energy and water. The industry also causes environmental pollution and degradation of natural resources.
How do you make concrete environmentally friendly?
Many alternatives are being studied to replace cement one of them is the mixture of fly ash with lime and water. This alternative eliminates the CO2 emission brought by processing of raw materials to cement.
What is the carbon footprint of concrete?
Cement manufacturing carbon footprint is projected to be for every pound of cement about 0.9 pounds of CO2 is being produced, thus, for 3900 pounds of concrete 400 pounds of CO2 is being released. This is equivalent to CO2 being emitted by using a computer for a year or by using a microwave oven for a year.
Is concrete toxic?
Cement is highly toxic which can cause skin and respiratory tract irritation. Cement dust contains calcium oxides, chromium, and silica. Inhalation of calcium oxides are corrosive to human tissue, chromium can trigger allergic reactions, and silica can lead to asthma, tuberculosis, and kidney disease.
Is concrete bad for soil?
Concrete affects the soil by raising the pH of the soil. The calcium carbonate component of concrete once leached to the soil increases the pH making it more basic.
References:
[1] Mittelman, E. The cement industry, one of the world’s largest CO2 emitters, pledges to cut greenhouse gases. Yale Environment 360 (2018). https://e360.yale.edu/digest
[2] Ehrlich, B. Reducing environmental impacts of cement and concrete. Building Green (2010). https://www.buildinggreen.com
[3] Ozcan, O., Musaoglu, N., Seker, D.Z. Environmental impact analysis of quarrying activities established on and near a river bed by using remotely sensed data. Fresenius Environmental Bulletin 21(11):3147-3153 (2012).
[4] Adeyanju, E., Okeke, C.A. Exposure effect to cement dust pollution: a mini review. SN Appl. Sci. 1, 1572 (2019). https://doi.org/10.1007/s42452-019-1583-0
[5] Zainudeen, N., Jeyamathan, J. Cement and its effect to the environment: A case study in SriLanka. Fraunhofer IRB: 1408-1416 (2002). https://www.irbnet.de/daten/iconda/CIB11336.pdf
[6] de Best, R. Global construction industry spending 2014-2019, with forecasts up until 2035. Statista (2020). https://www.statista.com/statistics/788128/construction-spending-worldwide/
[7] Watts, J. Concrete: The most destructive material on earth. The Guardian (2019). https://www.theguardian.com/cities
[8] Revels, G. 19 Eco-friendly concrete alternatives. Pro Crew Software (2020). https://procrewsoftware.medium.com/19-eco-friendly-concrete-alternatives-6382658800ac
[9] Rodgers, L. Climate change: The massive CO2 emitter you may not know about. BBC News (2018). https://www.bbc.com/news/science-environment-46455844
[10] Dezem, V. Cement produces more pollution than all the trucks in the world. The Economic Times News (2019). https://economictimes.indiatimes.com/news/international/world-news.
