Positive:
When built well, concrete can last for hundreds of years. It can be seen that concrete structures built in the 1800s were still in good condition in 1983. There are even specific types of concrete that are designed to last wherever it is built, such as earthquake-proof buildings in Japan. Once concrete is built, it can be safe to say that it will stay there for at least few thousand years, if not a few hundred thousand.
The raw materials to make cement is generally evenly distributed around the world. This means that all the material to make cement and the cement itself can be sourced locally. Therefore, there is no need for additional emissions from transportation to deliver materials to make the cement. (MEKA, 1987)
Negative:
Concrete is so widely used that it produces over 7% of the world’s CO2 emissions. Producing one tonne of Portland cement releases around a tonne of carbon dioxide into the atmosphere. (UNEP, 2011) The production of cement releases CO2 from the heating of limestone, and the burning of fossil fuel to heat the kiln. When calcium carbonate (limestone) is heated, it goes through a process called calcination where it breaks down into calcium oxide and carbon dioxide. It is estimated that this reaction emits 530 kilograms of carbon dioxide per tonne of portland cement produced. In 2014, the top 10 producers of cement have produced 4,045 million tonnes of cement. This shows that about 2 billion tonnes of CO2 has been released in 2014 from the calcination of limestone related to cement productions. (Netherlands Environmental Assessment Agency, 2015)
Calcium Carbonate -> Calcium Oxide + Carbon Dioxide + heat
CaCO3 → CaO + CO2 ΔH = 178 kJ/mol
Fossil fuels are burned up in order to heat up the kiln to reach the temperatures needed to create cement. Fuel combustion emissions used towards the production of cement is approximately equal to the total emission of calcination, which means that roughly 8% of the world's CO2 emissions in 2014 come from the production of cement. (Netherlands Environmental Assessment Agency, 2015)
Although this is a concerning issue, cement, per tonne, requires much less energy than other building materials such as steel or wood. It is only because we use so much of concrete that the carbon emissions are this high. Currently, scientists are trying to find different ways of producing concrete that doesn't produce that much carbon dioxide. One of the areas of research is making a super-strong concrete - so that less concrete is needed to do the job.
When built well, concrete can last for hundreds of years. It can be seen that concrete structures built in the 1800s were still in good condition in 1983. There are even specific types of concrete that are designed to last wherever it is built, such as earthquake-proof buildings in Japan. Once concrete is built, it can be safe to say that it will stay there for at least few thousand years, if not a few hundred thousand.
The raw materials to make cement is generally evenly distributed around the world. This means that all the material to make cement and the cement itself can be sourced locally. Therefore, there is no need for additional emissions from transportation to deliver materials to make the cement. (MEKA, 1987)
Negative:
Concrete is so widely used that it produces over 7% of the world’s CO2 emissions. Producing one tonne of Portland cement releases around a tonne of carbon dioxide into the atmosphere. (UNEP, 2011) The production of cement releases CO2 from the heating of limestone, and the burning of fossil fuel to heat the kiln. When calcium carbonate (limestone) is heated, it goes through a process called calcination where it breaks down into calcium oxide and carbon dioxide. It is estimated that this reaction emits 530 kilograms of carbon dioxide per tonne of portland cement produced. In 2014, the top 10 producers of cement have produced 4,045 million tonnes of cement. This shows that about 2 billion tonnes of CO2 has been released in 2014 from the calcination of limestone related to cement productions. (Netherlands Environmental Assessment Agency, 2015)
Calcium Carbonate -> Calcium Oxide + Carbon Dioxide + heat
CaCO3 → CaO + CO2 ΔH = 178 kJ/mol
Fossil fuels are burned up in order to heat up the kiln to reach the temperatures needed to create cement. Fuel combustion emissions used towards the production of cement is approximately equal to the total emission of calcination, which means that roughly 8% of the world's CO2 emissions in 2014 come from the production of cement. (Netherlands Environmental Assessment Agency, 2015)
Although this is a concerning issue, cement, per tonne, requires much less energy than other building materials such as steel or wood. It is only because we use so much of concrete that the carbon emissions are this high. Currently, scientists are trying to find different ways of producing concrete that doesn't produce that much carbon dioxide. One of the areas of research is making a super-strong concrete - so that less concrete is needed to do the job.