It is the teenagers and twenty somethings that are pointing their fingers at the system saying we need change to avoid environmental collapse. It may come as a surprise, but let’s think about it, this is the generation that has advanced to boast the most considerable rights, considering that their life expectancy is more than double compared to that of a fifty-year-old today. It will be them, their children, their grandchildren, and so on, who will have to take charge of a planet on the brink of collapse. All this is imbued by the rhetoric of the climate summits where the governments solely promised that by 2020,,,30 and…40 emissions will be reduced by a huge amount. Then let’s start the electric cars, the self-extinguishing shopping bags, the towels that should not be thrown away after the first use and all the other technologies that are rising to face this challenge. In all this dramatic change of climate there is a substance or rather a material that, despite being one of the main culprits of global emissions almost never brought to the dock. If this substance were a country, it would alone be the third largest producer of greenhouse emissions after China and the USA. Since no one speaks of it clearly, I have called it the “silent killer” of the planet, but it has a name and is called cement.
A few months ago, a friend who was stuck in traffic told me on the phone that he couldn’t stand to queue up for most of his daily transfers. “All this,” he said, “would inevitably lead to the collapse of our system. The enormous quantity of emissions that our cars release into the atmosphere is killing us”. I tried to reassure him by saying that cars aren’t the greatest killers. He replied with a questioning grunt: “What then would this first killers be?” “Cement,” I told him. Frustrated, he cut off the call, adding that the cement was a “neutral substance.”
It is difficult to explain the consequences of a process only known to experts. When you see being poured from a cement mixer, it is hard to guess it as a killer. Or better saying, it has been, because in the moment it leaves the duct, the crime has already been committed. The crime proofs must be sought in its manufacturing process in form of milions of tons produced and exponentially accumulated.
In 2018, the global production of cement was 4.1 billion tons. In this case the equation is simple: for every ton of cement produced, one ton of greenhouse gases is released into the atmosphere.
To be precise, there are two leading causes of emissions in the production process. A chemical reaction causes the first one. The calcareous rock extracted from a quarry is progressively crushed and reduced to granules of about 3 cm in diameter. Later, binding substances are added and the obtained substance is conveyed to industrial rotating kilns – about tens of meters long and up to six wide.
Here limestone and clay are cooked together at a flame temperature of about 2,000 degrees. At the operating temperature of 1500 °, the limestone dissociates into calcium oxide and carbon dioxide. Thus clinker is formed, an artificial mineral that comes out of the oven and is then air-cooled. Gypsum and ash from thermoelectric power plants are then added to the clinker, and the mixture is further ground. Cement is obtained as a final result.
The second cause of emissions is the energy consumption required to activate the process. In a cement plant, 60% of CO2 emissions come from the decarbonation of limestone, which is formed by calcium, carbon, and oxygen. Vast amounts of heat must be provided to activate this process.
The cement industry is an energy-consuming hell.
To manufacture one ton of clinker, it requires 3,200 to 4,200 MJ (Mega Joules). On average, the Italian cement industry consumes 2.3 million tons of non-renewable fossil fuel each year. If the CO2 emissions due to decarbonation are unavoidable, it is still possible to intervene by reducing the remaining 40%, deriving from the use of fossil fuels in the kiln.
The use of alternative fuels such as biomass produced from urban waste could lead to a reduction in emissions. According to Aitec (the Italian technical and economic association of cement), the use of alternative fuels in Italian cement plants, at current levels of use, makes it possible to avoid the emission of over 300,000 tons of CO2 per year. Nonetheless, this proposal tends to clash with the general idea that any waste used in a combustion process leads to further emissions; ; this is untrue, as far as bio-masses. managed in a controlled process, are concerned.
Even though we are witnessing more and more attempts to “green cement” production, we realise that this expression is almost an oxymoron. There is very little in the current process and in the additives to be able to mitigate the environmental impact of cement, indeed. A chemical reaction is always a non-return reaction. What is extracted from the soil and forced into an industrial process cannot be redefined as sustainable: it is merely a subtraction of resources leading an irreversible process.
It is from here that we need to start again.
Consider a tree, as a sustainable alternative: after cutting it, you can, at least, replace it with a new one. These joint actions become a sustainable one. Precisely because it is implemented organically and reversibly: the cut tree is replaced. Simple right?
The Mass Timber industry, or in other words, the engineering of a reversible process, is the only real viable alternative to cement.
Cement is a great invention that will always be present but indeed confined to areas where it is essential, and when there are no other chances. Cement is a great invention that will always be present but needs to be confined to areas where it is essential, and when there are no other chances.
When Waugh and Thistleton Architects designed their first multi-story timber building in London in 2009, they showed that an equivalent concrete and steel building would release up to 125,000 kg of carbon into the atmosphere. The use of CLT saves 185,000 kilograms of CO2, for a combined saving of about 300,000 kilograms of carbon. CO2 savings can only happen through the downsizing of carbon-emitting industries and the acceptance of a technology able to learn from nature.