Using bacteria to 'grow' concrete

[awhicker84]

Hi,

About 6 months ago, I learned about the possibility of a microbe that uses urea, carbon dioxide, and calcium to create Calcium Carbonate. It's an interesting microbe because it could help to sequester CO2 in the air. Problems of Cradle to Grave carbon cycles probably make it a bad candidate to simply use with shipments of urea and calcium, something that I haven't looked into yet.

I was interested in looking into the possibility of using this microbe in sanitation. (That requires a ton more research) However, a few others have found this microbe useful in the creation of concrete. I build furniture on the side (mainly woodworking). I am almost done with a dining room table project which should free me up. I came across this article of a guy making simple furniture from microbial concrete. I'm thinking I'd like to try and make an above the counter 'concrete' sink with this method.

https://www.zdnet.com/article/for-a-better-concrete-mix-sand-with-bacteria-and-urea/

https://www.matec-conferences.org/articles/matecconf/pdf/2017/17/matecconf_iscee2017_05016.pdf

Anyone have experience that would help?

Cheers,

 

[moltenmetal]

I'm afraid that someone with an inadequate understanding of chemistry is claiming that this process doesn't generate greenhouse gases.

Calcium is added to this process in the form of calcium chloride. How is calcium chloride made? One of two ways: a) by reacting natural magnesium chloride in brine with calcium hydroxide or b) reacting calcium carbonate (limestone) with hydrochloric acid. In both cases, what's the source of calcium? Calcium carbonate, i.e. limestone. And where does its CO2 (i.e. the carbonate) go? To the atmosphere. The CO2 in limestone is fossil CO2, just like what you get when you burn coal or petroleum or natural gas.

Similarly: how is urea manufactured? Though obviously we produce it as a byproduct of metabolism and excrete it in urine, industrially it's produced from ammonia and CO2. How do we make ammonia? By reacting hydrogen with nitrogen. Where do we get the hydrogen? And the CO2 to make the urea? Both come from natural gas. Though it's possible to make hydrogen, and hence urea, using solar or wind electricity by electrolyzing water, in practice 95-99% of hydrogen production is derived from fossil fuels.

At the end of all of this, you're trying to re-generate calcium carbonate as a kind of "glue" that holds other materials (sand) together. In artificial concrete, carbonate rocks and silicate clays are roasted using fossil energy, releasing CO2 both from the firing of the kiln and from the roasting to produce calcium oxide and silicates. Over the ~ 100 yr curing process of concrete, some but not all of that CO2 emitted by roasting the rocks is re-absorbed by the concrete, producing calcium carbonate. But all of the CO2 produced by burning fuel to run the kiln, ends up in the atmosphere.

What this microbial process does is replaces some of the energy use in conventional cement-making with energy use to make urea and calcium carbonate. It does nothing for the environment.

Want to make something out of calcium carbonate without generating much fossil CO2? Find a chunk of limestone, then carve what you want out of it using either manual labour or electricity derived from wind or solar. Or you could fire a kiln electrically to make conventional cement.

 

[awhicker84]

I recognize that it creates CO2 / greenhouse gases. It 'may' create less than normal concrete manufacture. A cradle to grave would need to be done.

 

[awhicker84]

https://link.springer.com/article/10.1007/s00253-016-7370-6

It's being studied quite a bit. Don't quote me, but I think that concrete production accounts for 5% of the greenhouse gases added to the atmosphere annually. Even a small decrease in the energy required would be a big win.

 

[awhicker84]

It's also fair to point out that you start with the simplest method: pure urea. After you are comfy, you can start attempting to work with more complicated materials, like urine, to replace the more expensive urea.

You have to start somewhere.

 

[moltenmetal]

Involving an organism in converting A to B using an energy source that you provide, is generally not a way to decrease energy consumption. Organisms are not very energy efficient- they tend to spend most of their energy staying alive and reproducing.