Artisans have been cooking limestone to make lime based paints and plasters for thousands of years; They still do it in traditional kilns near Seville, Spain, in a process that is recognized by Unesco. Graphenstone uses this lime to make paint, which it mixes with graphene, the wonder material that is, according to the UK distributor of Graphenstone paint, quoted in Dezeen,“ the strongest material now known to science. It was discovered in 2004 by two Nobel Prize winners at Manchester University. It is a highly inert, innocuous, nontoxic pure carbon.” It sounds like an interesting product, wonderful and green, so I thought TreeHugger should have a look.
They claim that the paint is sustainable and “carbon neutral –as the paint cures and over its lifetime each square metre of Graphenstone paint absorbs 120 grams of CO2 from the local environment where it’s applied.”
This is a function of the lime cycle; you make the stuff by heating limestone to make quicklime. This releases a lot of Carbon Dioxide, and is why the production of cement is responsible for over five percent of the world’s CO2 production. As the lime sets or in this case, the paint cures, that CO2 is re-absorbed as it reverts to calcium carbonate. The problem is that fully half of the CO2 produced by the conventional lime industry comes from the natural gas or coal used to heat the limestone. So you cannot call conventionally made lime carbon neutral.
But in the case of Graphenstone, the limestone is cooked in traditional wood-fired kilns. Because trees sequestered carbon as they grew, many people (particularly in Europe) claim that burning wood is carbon neutral. But wood actually produces a lot of CO2 per unit of energy. Using wood to make lime in a hundred and fifty year old kiln design is going to be hugely inefficient, its going to release a big whack of CO2 that was stored over centuries right now, along with a lot of particulate pollution.
I do love supporting artisan craft production, and acknowledge the claim of carbon neutrality (even though I do not believe that burning wood is carbon neutral) but in my opinion burning wood to make lime cannot possibly be considered sustainable and green.
That’s the low tech part of the paint, now the high tech. Graphene Company director Patrick Folkes tells Dezeen about its wonderful properties as a paint:
For the first time in history you've got this fusion of one of the oldest and most trusted building materials, lime, with the very latest nanotechnology….
Graphene is indeed very cool, high tech stuff. It is also very hard to make. According to the Cradle to Cradle certification, this graphene is made by "gas deposition, which enhances properties of flexibility, hardness, and thermal conductivity." It's also not very green; "the gaseous by-products of the process are usually very toxic. This is because the precursor gases used must be highly volatile in order to react with the substrate, but not so volatile that it is difficult to deliver them to the reaction chamber. " it takes a lot of graphite, chemicals and energy to make the stuff. It may be carbon, but it is not carbon neutral. But it does have magical properties when mixed with the lime paint:
When used on interior wall surfaces, rather than heat being radiated through the walls, the graphene within the paint captures the heat. It then conducts the heat through the paint, and across the whole Graphenstone-painted surface of interior walls. This enhances the insulation measures used in buildings by slowing heat conduction through walls and out of buildings.
On the Graphene Company website they say that graphene fibres are “1000 times more conductive than copper” and “As graphene is a conductive material, the paint improves the thermal regulation of buildings, saving energy by requiring less heating and air conditioning.”
Now I have no idea how much graphene is mixed into the plaster, (which is what the paint actually is) but it is expensive stuff, US$ 97 per gram so there probably isn’t a lot of it. It is a conductor, so I do not see how it enhances insulation. I am also dubious that anything the thickness of a layer of paint can make much difference at all. (Insulating paint, anyone? ) In fact I will just say that none of this makes any sense to me at all.
On the gorgeous Graphenstone website this paint is advertised as “the most advanced solution of ecological and natural, paints and coatings in the market.”
Lime and graphene combined form the ultimate ecological, natural coatings and paints in the world. This is why the Graphenstone products have great performance and covering properties. Thanks to their flexibility the coatings does not crack or flake off. It also contributes to energy savings due to its great reflective power. Moreover, thanks to its mineral character it reduces the reverberance of the sound. We design and manufacture with respect for the environment, the circular economy and energy efficiency; this is the reason why our products fit perfectly in Green or Eco Buildings, Passive Houses, and Smart Cities.
But when I look at how the lime and the graphene are actually made, I cannot call the lime ecological or the graphene natural. I just don’t get it.