Since I mentioned eco-products previously, I wanted to expound a bit on one aspect of them, embodied energy. Following is an excerpt from my presentation at the Living Green Workshop.
…Choosing sustainability often involves sifting through these options and finding the ones that are best suited to your site. Using a great eco-friendly, recycled product may not be the best sustainable choice if it requires being shipped clear across the world.
This ties to the topic of choosing appropriate building materials based on the concept of Embodied Energy. Embodied energy in buildings can be broken down into 2 categories: initial embodied energy and recurring embodied energy.
Initial embodied energy is the energy used to acquire, process and manufacture the building materials as well as the energy used to transport the products to site and construct the building.
The recurring embodied energy represents the non-renewable resources used to maintain, repair and replace components during the life of the building.
We can actually add another category that represents the energy used to dispose of the building components once they have reached the end of their life cycle. Embodied energy is an important measure of sustainable design.
According to the World Watch Institute:
Each year, 3 billion tons of raw materials are used for construction.
Buildings account for ½ of the global output of carbon dioxide.
Production of cement used in concrete accounts for 5-8% of that carbon dioxide.
To illustrate embodied energy as well as introduce you to the idea of exploring how our products are made I want to talk about concrete, more specifically the production of cement. Compared to other products, cement, the binder in concrete is high in embodied energy.
Cement starts off as raw materials, limestone and sand that are quarried from the earth using heavy equipment.
The materials are then crushed and mixed by more powered machinery then fed into a tilted rotary kiln. These rotary kilns are the largest piece of moving industrial equipment in the world. The mixture moves through the kiln, which gets progressively hotter to a temperature of approx. 3,000 F as it is continually fed coal or natural gas. This causes a chemical reaction and the materials fuse into what’s called clinker then the clinker is sent to coolers. Once cooled the material is crushed to a fine powder and ready to be bagged or sent directly to a concrete supplier. As you can see, a lot goes into making the glue in concrete before it even reaches our foundations. There are innovations in concrete production. Fly ash, a byproduct of coal burning plants can be substituted for a percentage of the cement. Also, pozzolan (volcanic ash) and magnesium oxide, which is mined or processed from seawater are other alternatives to cement….