Biochar Plaster and Biochar Bricks — 11 Comments

  1. I imagine the biochar plaster is very dark (nearly black). Is it generally used as a base coat then, with another layer on top that is lighter? I would love to see some pictures of biochar plasters with different pigments–this may provide some interesting artistic opportunities.

  2. What sources other than rice hulls are being marketed as biochar? Cotton seed hulls are available in our area but I am unsure how to turn them into biochar.

    • You should be able to use lots of different biomass products — whatever is cheap and abundant in your area. With a little experience you’ll figure out what works best.

  3. This is a top coat plaster which is suitable for a great finish on all the other surfaces. It’s main purpose it to be used as a finishing plaster when there are a variety of different backing surfaces to be covered. This is similar to Browning plaster, apart from that it offers a higher impact resistance and is a quicker drying surface. This is the most commonly used undercoat plaster used these days and can be applied to most masonry surfaces. This is an undercoat plaster, so the first coat, or undercoat, that would be applied. After being trowelled off, it is scratched with a nail to give a ‘key’ for the top coat, or finish plaster to adhere to. This plaster has real ‘stickability’, without needed an absorbent surface to bond to. This is a cement-based plaster which can be used when resurfacing a wall after the installation of a new DPC.   A full list of our different plaster types can be found on our Building Materials webpage.

  4. I did some trails using biochar/cement for agricultural fencing posts, made from balsa biochar (very common feed stock in rural Ecuador). Very interesting concept.

    My mix was about 4:1 biochar to cement, no sand, using 5.5mm rebar in a 15cm square, tied at 50cm intervals. Once dried the post was light weight and seemed to be strong – I didn’t get around to really testing it, and only made a couple. My problem was getting sufficient biochar, I need to make a proper kiln… but then there is the opportunity cost, is it not better to use the char for soil improvement than in construction?

    I don’t know if I would use it for anything structural, but that isn’t the idea!

  5. very interesting. I have used charcoal in earthen plaster before and it was quite successful. I’ll be following this development. Great post.

  6. In my area biochar is a low cost by-product of drying rice at a rice mill. The rice hulls are first removed from the rice kernels. Then the hulls are turned into biochar with controlled burning. The hot air from this process slowly dries the rice. We spread biochar on our garden every so often to build the soil.

    They sound pretty confident about biochar bricks. I’d love to get more info on this. Hopefully they’ll write some simple open source directions for owner-builders like the biochar plaster article above (great job).

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