Dwelling on Drawdown Part IV – About Grout (with biochar, of course!)

I absolutely love it when I come across contractors willing to consider more sustainable ways of doing things. Too often in my Dwelling on Drawdown (D0D) home-building journey the opposite has been my experience. But recently when I had my shower floor installed by Charlie B from Skip’s Custom Flooring, not only was Charlie willing to consider using biochar in the project, he was downright enthusiastic! I was a bit shocked to find out he’d been reading up on biochar for years and was hoping to build a kiln to char through lots of tree debris on his acreage. (Biochar is still mostly unknown in my part of the world.) We discussed possible ways of using biochar on this small project and tested it as a tint for the grout. Charlie also had other ideas about how biochar could be used in buildings but also knew that it is likely used in certain types of pottery (see La Chamba pottery from Colombia, or Raku from Japan). That was news to me – yet another tantilizing biochar rabbit hole for exploration.

The grout sample dried nicely so we mixed up a batch to use on the 48sf shower floor. It took a lot more biochar than I thought we’d need and we never got it to turn black though that wasn’t really my intent on this project. Roughly one pound was added to 2 gallons of grout . I’ve used Aries Clean Technology’s powdered biochar for other D0D projects and was a little surprised that it didn’t turn a darker shade of grey as it definately tinted my walls a very dark black as I’ve written about before. The only difference Charlie observed was that the mix was a bit ‘greasier’ than a more commercially available tinted grout, meaning it was slightly more difficult to wipe off the tiles when grouting was finished.

Black iron oxide or magnetite is what is commonly used as a black tint for grout and a whole host of other materials. Both natural and synthetic types are used in everything from construction materials, paints, coatings, and plastics, cosmetics, pharmaceuticals and even ceramics, and toners (Pfaff 2021). Imagine if we could start displacing some of that with different types of biochar?! We just need to understand the tinting abilities of different types of biochar across they gray to black spectrum. On our recent EPA project focused on using biochar in drywall we observed quite a variation in coloring based on feedstock types, particle size and obviously amount used.

How else could biochar be used in bathrooms? The plan for the shower walls is tadalakt plaster with a just a touch of biochar to tint it a lighter shade of gray. I’ve tested it out and it works great with a wide variation of grays possible (see picture). Next up though is my sink vanity top which is being custom made using epoxy and biochar. The epoxy artist has already done a test run and is now very interested in using biochar as his black tint is about $60 per pint! More on that soon.

[I know my BURN co-author would remind me that it can be used in composting toilets. Though I I didn’t go that route for my Dwelling on Drawdown, I do have an ‘emergency’ toilet in the basement with biochar in a bucket!]


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