People seem to have a reluctant relationship with Earth’s natural world. We know that nature provides us with our necessary food. But most of us buy it in shops. And, with most of us living in cities, even our homes and workplaces are removed from nature. For these, concrete is the most effective separator. It’s a human invented material that is the foundation for most of our civilization.
Concrete results from mixing cement with water and with a suitable filler such as sand or gravel. Its use in the Roman era Pantheon demonstrates its durability. Its longevity can be further enhanced as we use rubble from destroyed concrete structures as filler for new concrete structures. However, cement can’t be re-used. New concrete requires new cement. And cement is costly.
Let’s scale the cost. Annually we produce over 4×109 tonnes of cement, equivalent to the cement for about 1000 dams the size of the 3 Gorges Dam. This amount is to remain constant to well past 2050. Its production calls for an annual expenditure of 3.5GJoules of energy per tonne. This amounts to an allocation of 1.4×1019Joules of energy annually, about 3% of total energy consumption. As most of the energy comes from fossil fuels then there’s resulting pollution at a rate of 0.54t of CO2 per tonne of cement, about 8% of global CO2 emissions. Because of this, cement is a significant parameter when modeling future climate change. Over history, humans have used about 128×109 tonnes of cement to enable living apart from nature, which is almost a thousand times greater than the weight of all humans. Concrete is costly both in energy consumption and pollution emission.
Concrete separates us from nature. And estimates are that we will continue this separation for decades to come. Should we continue to separate ourselves from the ecosystem? Or are you willing to fight this apparent primal urge to treat nature as a threat? For a prosperous future, we recommend you look for ways to live with nature rather than apart.