Projects

Pollution and Cement

Earth building and rammed earth have very low carbon emissions. In this recently updated section the projections from 2007 have been left in to show how much faster cement emissions have grown in the past four years than our estimates at the time. Even with a global recession cement emissions are some of the fastest growing human impact.
Cement is a huge polluter. Some 10% of total carbon emissions are from the manufacture of cement, to say nothing of the associated transport burden. For every bag of cement there is a one and a quarter bag weight equivalent of carbon dioxide released. This is because the limestone which is burned to make cement is more than twice the density of water and has to be heated to 1,450 degrees C. In addition to the energy load to heat the limestone, the stone itself is composed of calcium and carbon. To make cement the extremely stable carbon, the living part of the creatures whose remains make up the limestone, has to be made into CO². In this way we have made two sources of very stable fossilised carbon into a huge amount of CO².
In doing this for the last 100 years we have produced a global construction sector which is now entirely client to the cement industry. Through legislation cement has become a monopoly material throughout the world, and for increasingly minor structures. Not only has cement dominated the legislative and codified areas of construction, it has dominated education in the professions and trades too. Most western educated engineers know nothing of any other form of construction, and as we are driven by an increasingly style oriented architecture the results are ever heavier burdens of pollution.
Other misconceptions about cement include its longevity. Not only has concrete cancer been identified as a big killer of concrete structures, users also destroy buildings with the same lack of concern over their consumerist values as with all other forms of consumption and waste. The difference is that cement has such a high burden of embedded energy that is not justified by the short life span of so much modern building, destroyed through internal faults or changes in fashion.