Green Building Forum - Biogenic limestone

Biogenic limestone

djh — Tue, 03 Oct 2023 18:16:53 +0100

Just came across an article about growing limestone using algae and then using the limestone to make cement.

https://www.ribaj.com/products/microalgae-grown-limestone-for-concrete-university-of-colorado-boulder

The algae absorb CO2 from the environment as they grow and that is released when the cement is made, using an electric furnace of course. So carbon neutral cement; and if the limestone is also used as aggregate, carbon absorbing concrete.

They talk about cost parity with conventional cement and using 1-2 million acres of land to generate limestone for US building.

Which all sounds very promising. If they just produce limestone perhaps it's also a practical carbon capture method.

What's the gotcha?

Biogenic limestone

tony — Tue, 03 Oct 2023 23:16:06 +0100

! Sounds like snake oil accounting. I am not big on carbon but making cement releases it into the atmosphere so does burning algae.

I like trees they absorb carbon, lime realeases carbon when it is being made and recaptures it over the next 100 years, concrete is inert burning itâ€™s life

Odd claim

Biogenic limestone

WillInAberdeen — Wed, 04 Oct 2023 13:57:47 +0100

Algae have been suggested for all kinds of useful things - food, fuel, medicine, bioplastic - but so far it hasn't happened.

They don't grow on (farm)land and it's expensive to build artificial ponds and find enough water to keep those filled, and displace whatever wildlife/carbon/usage was already there. They need chemical nutrients added, and there are millions of other bugs that would like to grow in your nutrient ponds so more chemicals needed to kill those off. Then it's difficult to harvest and dry out the algae, separate out the useful products and dispose of the rest. The used water is an effluent problem.

Probably these are all solvable at some cost, but if the desire is to make biogenic limestone, then all limestone is biogenic. So use existing limestone for cement and make new limestone somewhere else. Schemes are proposed to create algal blooms in the sea by dumping in excess nutrients, which would fix carbon and then sink. There are obvious problems with this too.

Biogenic limestone

jms452 — Wed, 11 Oct 2023 19:47:23 +0100

Posted By: tony! Sounds like snake oil accounting. I am not big on carbon but making cement releases it into the atmosphere so does burning algae.

I like trees they absorb carbon, lime realeases carbon when it is being made and recaptures it over the next 100 years, concrete is inert burning itâ€™s life

Odd claim

Calcining the limestone rereleases the carbon captured during growth so the key (as dgh says) is also using the uncalcined carbon negative limestone in the mix to (either as an SCM or aggregate).

Having worked in this area the carbon story believably adds up although the cost parity is going to be hard, really hard, for all the reasons given by Will.

Biogenic limestone

djh — Wed, 11 Oct 2023 20:40:34 +0100

"The project was recently awarded a $3.2 million grant from the US Department of Energy and was recently selected by the programme Harnessing Emissions into Structures Taking Inputs from the Atmosphere, to develop and scale up the manufacture of biogenic limestone-based portland cement.

'"The only challenges that we face are cost and scale,' says Srubar. 'We are addressing this through the $3.2 million project. We have a clear pathway to deliver biogenic limestone at cost parity to traditional limestone and at a scale that can meet the demand of US cement production.'"

So it seems the US DoE believes in the project to some degree, and the PI seems to have a decent CV and something of a track history, so maybe they can make it work. (fingers crossed emoticon)

BTW, whilst googling for more info I came across this: https://www.treehugger.com/build-beyond-zero-book-review-5536909 Now King & Marwood are both very well known to me, since they've written books about building straw houses So I've ordered a copy

Biogenic limestone

WillInAberdeen — Wed, 11 Oct 2023 23:15:50 +0100

"at a scale that can meet the demand of US cement production.'"

Taking a step back, there are lots of minerals that can be used as binders for concrete, and there are lots of ways to use concrete more sparingly, and lots of ways of building without using concrete.

The reason why such huge quantities of limestone-based Portland cement concrete are used, is that it is amazingly cheap. The raw material is literally found lying around.

If limestone Portland cement were made even a little more expensive, people would choose alternatives instead.
- silicate rather than carbonate binders
- thinner concrete slabs and tapered beams
- block walls that are just as thick as necessary, rather than 215mm every time
- refurbished structures rather than rebuilds
- sites in places that dont need such difficult foundations
- timber, stone, clay, composites, biopolymers, earth, etc

All research is good, but the efforts seem misplaced to make the same old cement from different raw materials (but inevitably more expensive than just digging them out of the ground). JIMHO. Bit like making plant-based petrol to keep combustion engines running - better to use electric cars instead, or ride a bike.

Using algae to sequester CO2 into limestone seems great if the expensive bits can be worked out, [and the algae ponds couldn't be used for growing something more urgent.] The best thing to do with that limestone would be tip it in a big heap, rather than cook it back down to release the CO2 and make cement!

Edit to add: a lot of methane gets emitted from shallow rice-growing ponds/paddies, would be a problem if the million acres of algae ponds did the same.

Biogenic limestone

djh — Thu, 12 Oct 2023 11:55:43 +0100

The US DoE is investing in a whole raft of projects looking at new ways of building and making materials etc etc, so all power to their efforts. I support each of their efforts. We need more of them.

Biogenic limestone

fostertom — Thu, 12 Oct 2023 15:30:52 +0100

Posted By: djhI came across this:https://www.treehugger.com/build-beyond-zero-book-review-5536909" rel="nofollow" >https://www.treehugger.com/build-beyond-zero-book-review-5536909Now King & Marwood are both very well known to me, since they've written books about building straw houseshttps:///newforum/extensions/Vanillacons/smilies/standard/cool.gif" alt="" title="" >So I've ordered a copyhttps:///newforum/extensions/Vanillacons/smilies/standard/bigsmile.gif" alt="" title="" >

Glory be - at last! Someone's really named that game - been searching high and low for the concept.

Mind you, it's not just buildings that should be consciously designed to draw down carbon and lock it away (at least till the world has more headroom for allowing an interrupted carbon cycle to resume).

Not just buildings, but everything that humans make, from nanobots to phones to cars to houses to giant infrastructure, should be treated as an opportunity to not just shave %age points off its release of CO2e into the environment (which however worthy is still accumulation), but to actually leave the atmosphere better than if nothing had been made.

And not just carbon - likewise, everthing that humans do should be designed to actively remove, re-purpose or safely stash the vast number of other environmental pollutants, from bio-active electromagnetic radiation, to chemicals and inorganic wastes (plastic) to noise to light pollution.

The ability to conceive of the concept, and the science to make it all possible, is growing. This book sounds to lay it out very specifically. I've ordered mine - cheapest seems to be
https://www.ebay.co.uk/itm/314145503088?_trkparms=amclksrc%3DITM%26aid%3D1110006%26algo%3DHOMESPLICE.SIM%26ao%3D1%26asc%3D20201210111314%26meid%3Dc65d51dfdf2f427bab3c69d1936f1c35%26pid%3D101195%26rk%3D1%26rkt%3D12%26sd%3D355096036363%26itm%3D314145503088%26pmt%3D1%26noa%3D0%26pg%3D4429486%26algv%3DSimplAMLv11WebTrimmedV3MskuWithLambda85KnnRecallV1V2V4ItemNrtInQueryAndCassiniVisualRankerAndBertRecallWithVMEV3CPCAuto&_trksid=p4429486.c101195.m1851&amdata=cksum%3A314145503088c65d51dfdf2f427bab3c69d1936f1c35%7Cenc%3AAQAIAAABcObhgc4Nk8%252BdtAwOww4FKLaj%252FQ5qqgDlQCuqZA43WcPFUWDERCUugbbOk7XQv0JXlBfqCg2xKF3WcPghxGMFw2oSlXvfExEaMYr7I7LmrHcP6czY1wIMt0ORyKiCWt95xldincyyBx3g%252BNDW%252B%252FhWUgTaBhK6xAm%252BJIbCOMehu%252BdwmimyPh%252BWYNLm%252FAXz%252BxC2fJwkatgpGUFvbGYiRK95OrEEtggncuCA9V%252Btz%252BrnMvzX4x06KBn5wjXX6zLSSwt1I%252F9bFrN26inl2QZxZmBnJAKuQvrzLJSxcG%252FBk2GF%252F4wMuT1Fo96nUyx8zB9ExnYvZIO0n2XBapychQTW%252Fh7jEEyhuMUYSBAnvITT7UrH6Eodc7jS3itTkLCWybNaFsr6hzf3Kyo1i9URHc8XM8WJ7IkoDyhlg1%252BUisAyJaA5Xe2q1HNWMdivDqhezMPZBGNwY79d7vLScIEACfhd%252FqIbPFm6fQcRE%252FDGBPHV%252BY2revLd%7Campid%3APL_CLK%7Cclp%3A4429486&epid=20054676612

Biogenic limestone

jms452 — Thu, 12 Oct 2023 16:36:23 +0100

Posted By: WillInAberdeenAll research is good, but the efforts seem misplaced to make the same old cement from different raw materials (but inevitably more expensive than just digging them out of the ground). JIMHO. Bit like making plant-based petrol to keep combustion engines running - better to use electric cars instead, or ride a bike.

Agree with the sentiment - the challenge is that concrete is the most used material on earth (lots of sensible substitutes like wood are already heavily utilised and just don't exist in the requires volumes to be even close to a replacement). Concrete is also well understood in a conservative industry where newfangled concrete like materials from yesteryear keep biting us on the ass.

The vision (e.g. CBAM) is that the carbon externalities get priced-in, making high-carbon materials like concrete more expensive and encouraging more efficient use, 'green' substitutes and other alternatives. Industry then does what it does best picking the cheapest option (but now with the externalities priced in).

Biogenic limestone

djh — Thu, 12 Oct 2023 17:17:30 +0100

Here's another wild idea: https://www.degruyter.com/document/doi/10.1515/eng-2022-0390/html

I imagine 'regolith' is available on the earth too.

Biogenic limestone

jms452 — Thu, 12 Oct 2023 19:43:18 +0100

It's very cool!

made this co: https://www.deakinbio.com/s-projects-side-by-side

note that 'Starcrete' is made with a starch binder so not 100% waterproof - hence the Starcrete concept (i.e. not much liquid water up there)!

Biogenic limestone

djh — Thu, 12 Oct 2023 20:23:21 +0100

Ooh thanks. I hadn't realised it was a UK thing. Starch has been used for quite while as a binder. According to https://www.roquette.com/innovation-hub/pharma/expert-opinion/starch-wet-granulation-binder it isn't soluble in cold water? I've asked the company about its use on earth

Biogenic limestone

fostertom — Mon, 23 Oct 2023 09:56:13 +0100

'Build Beyond Zero', as mentioned above, is the new book everyone should get - a revelation and practical source-book, recasting and updating our ideas of what the task of Green Building should now be. Buildings not merely nett-zero, but as active carbon-drawdown machines.

If 'in use' energy is by now a 'known' science and practice (even if pathetically un-adopted), the focus shifts to the newer science of embodied energy (esp the manufacturing industries, such as glass), as it's where greatest carbon draw-down/sequestration can happen, has the most up-front immediate climate impact, and has the longest-term effect on the total impact of a building's lifetime.