It's been said that building materials should be so healthy that you could eat them. Foam insulation doesn't usually meet that criterion, being made from fossil fuels, foamed with greenhouse-gas propellants and filled with flame retardants. But here is a recipe for a new kind of foam, cooked up by Chinese researchers led by Yibin Li at the Harbin Institute of Technology, that might change that picture. It is something you might bake up at home, if you had a laboratory oven filled with argon gas. It is essentially bread that has been cooked until there is nothing left but a carbon foam.
Just follow the recipe:
- Mix up flour, yeast and water, hold the salt, knead, let rise.
- Bake for 18 hours at 80°C (~175°) until dry.
- Do second bake in laboratory tube furnace filled with argon gas until completely carbonized.
- Slice and serve as fireproof rigid insulation, electromagnetic shielding.
- Tune and adjust recipe "by changing the amounts of yeast and water, which would allow it to be used for a variety of different applications."
Really, making healthy, fireproof insulation could be as easy as baking a cake, resulting in a pure carbon foam, and probably not very expensive at that. And such a simple, logical, "why didn't I think of that" idea, as Charlie Sorrel of Fast Company notes:
The combination of low-cost, tunable inner structure, and ease of manufacture could make carbon foam into a very useful material, with all kinds of applications. And to think, you could have invented it yourself, if only you hadn’t lent your argon-filled laboratory tube furnace to that cousin who never returns your stuff.
Technical stuff from the abstract:
In this work, lightweight and stiff carbon foam (CF) with adjustable pore structure was prepared by using flour as the basic element via a simple fermentation and carbonization process. The compressive strength of CF exhibits a high value of 3.6 MPa whereas its density is 0.29 g/cm3 (compressive modulus can be 121 MPa). The electromagnetic interference (EMI) shielding effectiveness measurements (specific EMI shielding effectiveness can be 78.18 dB·cm3·g–1) indicate that CF can be used as lightweight, effective shielding material. Unlike ordinary foam structure materials, the low thermal conductivity (lowest is 0.06 W/m·K) with high resistance to fire makes CF a good candidate for commercial thermal insulation material.