What is the energy use to produce a piece of burnt clay bricks ?

Question

What is the energy use to produce a piece of burnt clay bricks ?

Answer 1

For burned clay bricks ( not sun-dried mud bricks ) you need to heat clay to a temperature of close to 1900 degrees Farenheit, just at the edge of melting point for silica.  Sitting in the sun won't ever do that, it will take a lot of energy.  Something to keep in mind though, clay brick factories keep their kilns hot 24 hours a day almost all year, so they almost never have to start from "room temperature", they only need to maintain the heat they already have.  The ultra-heated bricks are let out of the kiln slowly, and the heat that dissipates from them keep the area close to the kiln hot, so the heat isn't totally wasted to the air outside.  Heat is used efficiently to save costs, to run the equipment efficiently and to prevent too sudden cooling of the bricks which could cause heat-shock / shrinkage cracks.  

If you're worried about the environmental impact of clay bricks, think of all the other issues, the raw material is natural, chemically stable material with no poisons, the finished product, likewise.  Clay brick can last centuries and never emit chemicals or metalic oxides, and almost all of it never need to be replaced.  Even if bricks are torn down and put in landfill, its just clay, virtually rock that's been reconstituted, and will change its  form back to clay.  No poisons.

Answer 2

If the process is heated by the sun, fired clay brick takes  time  and a bit of reflective material, but not a lot of energy. A well designed solar kiln will usually have a wheel turning horizontally, carrying the brick to provide even firing. It may take 200 watts to run that wheel.

Most kilns designed to be fired by wood will not be extremely efficient, so the energy lost may far exceed the energy actually needed.