The Guardian is treating us to an entire week’s worth of stories about how evil concrete is. It paves over the land the bugs live on d’ye see? The bit about us being able to live efficiently on our concrete platforms, thereby leaving more land available for the bugs, rather passes them by.
However, there’s a rather larger lack in their analysis. They insist that concrete manufacture produces CO2 emissions. They’re right there, it does. It’s not entirely obvious that there’s a solution here for the manufacture of concrete is, at a certain level of understanding, the production of CO2 emissions. We’re actively trying to drive the CO2 out of the source materials in our manufacturing of concrete, that’s the point.
So, much for concrete then and the 6% or so of global emissions it causes.
Except we do rather need to ask why are we making the concrete? The answer being that the value of it comes from the absorption of CO2 over the life of the concrete in use. We drive it off to make something we can play with, then once we’ve played we allow it to set. Concrete setting being, again at a certain terribly simplistic level of understanding, allowing CO2 back into the concrete.
That’s something we really should be told, don’t you think?
Concrete: the most destructive material on Earth
Seems a bit de trop doesn’t it? I’d put human idiocy as the most destructive thing upon Earth but if we’re to restrict ourselves to materials I’d suggest study guides in any of the grievance studies.
It also magnifies the extreme weather it shelters us from. Taking in all stages of production, concrete is said to be responsible for up to 8% of the world’s CO2. Among materials, only coal, oil and gas are a greater source of greenhouse gases. Half of concrete’s CO2 emissions are created during the manufacture of clinker, the most-energy intensive part of the cement-making process.
OK, but we really do need to be told the other part of this:
What most people do not realize is that the release of carbon dioxide from calcination in the manufacture of portland cement may also be part of a cyclic process and is partially carbon neutral in smaller timeframes such as decades and may be fully carbon neutral in longer timeframes. It is easy to picture the organic portion of the carbon cycle with respect to plants as previously mentioned; carbon is absorbed through photosynthesis and released through respiration or decomposition. Inorganic forms of solid carbon such as rock are also part of the carbon cycle. Rocks and other minerals are by far the largest sinks of carbon on Earth and they can weather or decompose, either naturally or through anthropogenic processes such as in cement kilns. The carbon dioxide released to the atmosphere is naturally in constant flux with other large sinks, such as the oceans and other surface waters, where it dissolves and through a variety of both organic and inorganic calcareous processes, such as reef formation and precipitation, settles back into the Earth’s crust.
However, concrete can also absorb carbon dioxide and store it in a process commonly referred to as carbonation. This may be viewed simply as an additional, alternative loop of the complex carbon cycle. Carbon dioxide may be absorbed by concrete in its many forms such as buildings, bridges and pavements (Figures 1a, b and c). Concrete does not even necessarily have to be directly exposed to the atmosphere for this process to occur. Underground concrete piping and foundations can absorb CO2 from air in the soil, and underground and underwater applications might absorb dissolved carbon dioxide (carbonates) present in groundwater, freshwater, and salt**ter.
The Guardian. Partial, alarmist and misleading. Who would have thought it, eh?