Cement is one of the most widely used materials in construction. Applications include concrete floors, walls, and pavement; concrete blocks; and different mixtures of mortar and grout.
Thousands of construction workers are exposed to concrete every day without harm. But anyone who uses or supervises the use of cement should know its health hazards and the safe working procedures necessary to minimize exposure.
Manufacturing the stone-like building material is responsible for 7% of global carbon dioxide emissions, more than what comes from all the trucks in the world.
Tremendous Pollution Impact
World production of cement is currently around 3.6 billion tons per year and this is set to rise to around a billion tons by 2050 as the standard of living in developing countries continues to accelerate. In fact, in terms of volume used, it is the most important substance on Earth bar water.
Though cement is extremely useful and an integral part of modern society, it is not environmentally friendly.
To create cement, the constituent limestone must first be heated, and this is undertaken on an industrial scale using fossil fuels, which inevitably leads to CO2 being poured into the atmosphere. Cement production is one of the worst polluting industries in USA, and accounts for 5% of all carbon dioxide emissions globally. In general, every ton of cement produced leads to a ton of carbon dioxide gas being released into the atmosphere. Other harmful emissions from the Portland cement manufacturing process include nitrogen oxides, sulphur oxides and carbon monoxide.
There is also the inherent environmental impact of quarrying the limestone for production and transportation of the finished product. The mining of the constituent minerals needed for cement can cause large amounts of subsidence and various types of pollution.
Cement’s contribution to emissions is especially immense because of the chemical process required to make it.
About two-thirds of the polluting gases that come from cement production stem from burning limestone. Kilns are heated to more than 1,400 degrees Celsius (2,600 Fahrenheit), about four times hotter than a home oven set to the self-clean cycle. Inside the kiln, carbon trapped in the limestone combines with oxygen and is released as CO2, the most abundant greenhouse gas.
A ton of cement yields at least half a ton of CO2, according to the European Cement Association. That’s more than the average car would produce on a drive from New York to Miami. And a single mixer truck can carry about 13 tons. Hundreds or even thousands of tons go into ordinary office buildings.
The scale of the problem has drawn the attention of research groups like the IEA and Chatham House along with policymakers from the C40, which represents the world’s largest cities. The IEA estimates cement production will rise 12% to 23% by 2050, though it could cut emissions with a series of actions. All the groups are looking for levers to prompt change.
Move towards green cement
Today green cement production accounts for 3.5% of global cement, but is forecast to grow to over 13% of the market by 2020.
Large cement producers have realised the environmental impact of cement for quite some time and have trialled eco-friendly alternatives.
Early attempts to produce ‘green’ cement included adding by-products to reduce the amount of limestone needed: steel by-products (slag), ash and more magnesium oxide have all been trialled with varying levels of success.Furthermore, by adding more magnesium oxide to Portland cement it was hoped that the temperature of production could be lowered to a temperature that was achievable by heat produced using biofuels. Unfortunately, as the heating of magnesium oxide produces substantial CO2 the use of MgO did nothing to reduce emissions of the overall process, sometimes doubling emissions relative to traditional production.
Other temperature reducing minerals were also tried, but the exact chemistry of Portland cement is not well known and it is hard to predict how the chemical reaction which hardens the cement would be affected by the addition of extra minerals.
However, there are many companies that are still working with different blends of Portland cement to try and create a sustainable alternative.
Brazil is one place making rapid progress, partly because of the availability of raw materials such as pozzolan, a type of siliceous and aluminous material that results in a product with the same technical properties as the traditional cement.
Although green cement production will, initially, be confined to developed countries, China and India will catch up quickly given their dominance on the world cement scene.
These are the conclusions from a new study entitled The Future of Green Cement to 2020. Based on extensive primary research and expert technical and market insight, the study also reveals how demand for alternative cement-like materials will grow from almost nothing to just under 17 million tonnes over the next ten years.
Cement is perhaps one of the most necessary and widespread resources in the world. At the same time, there is no viable replacement for cement, and the cement industry has a heavy impact on the environment. In terms of carbon dioxide (CO2) emissions alone, the cement industry produces about 5% of man-made CO2 emissions globally.
Fortunately, many practices are increasingly proving to reduce or eliminate the environmental impact of the production process without degrading the quality of the end product. Such practices include:
- The use of recycled materials
- The use of alternative fuels
- The use of value-added raw materials such as geopolymers
- Industrial symbiosis (synergy)
- Sequestration of carbon dioxide
- Dry process technologies
- Oxygen kilns.
Several technologies have been developed that can promote sustainable practices in the cement industry. Implementing environmentally and socially beneficial practices can often be economically beneficial as well in the long term, directly or indirectly.Cement production trends will be the continual development of more sustainable practices, and the industry will experience more societal and legal pressure to implement these practices.
The focus is on efficiency and using fossil-fuel alternatives for heat. The European Cement Association says its producers already get 44% of their energy from cleaner sources and wants to raise that proportion to 60% by 2050. Instead of using coal, it’s creating heat with used tires, mineral oil and industrial waste.
The next frontier would be using carbon capture and storage devices to siphon off pollutants and trap them underground permanently. That technology isn’t in widespread use and would be expensive – hundreds of millions of dollars for each factory – but it could reduce emissions 80% by the middle of the century.
Conclusion
The cement industry faces a number of challenges that include depleting fossil fuel reserves, scarcity of raw materials, perpetually increasing demand for cements and concretes, growing environmental concerns linked to climate change and an ailing world economy. Every tonne of Ordinary Portland Cement(OPC) that is produced releases on average a similar amount of CO2into the atmosphere, or in total roughly 6% of all man-made carbon emissions. Improved production methods and formulations that reduce or eliminate CO2 emissions from the cement manufacturing process are thus high on the agenda.
