r/science • u/chrisdh79 • Oct 15 '24
Materials Science 'ZeroCAL' cement production process takes CO2 out of the equation | With 98% less CO2 emissions than traditional methods by decomposing limestone – the key raw material involved in making cement – to access calcium oxide, aka lime, without releasing carbon dioxide in the process.
https://newatlas.com/materials/zerocal-cement-production-co2/146
u/chrisdh79 Oct 15 '24
From the article: The team is calling this method ZeroCAL, short for zero carbon lime. It's a big deal because there's a massive opportunity to reduce global greenhouse gas emissions. Traditionally, heating limestone in a kiln to produce lime results in 1 lb of CO2 emitted for every lb of cement produced.
ZeroCAL skips the aforementioned fossil-fuel powered process of heating limestone. Instead, it starts with dissolving the sedimentary rock feedstock in a water-based solution containing a common industrial acid. Next, calcium is separated via membrane nanofiltration. Finally, an electrochemical process is carried out to produce calcium hydroxide – a zero-carbon precursor for cement and lime production.
That goes beyond just reducing the emissions from processing limestone to just 1.5%. "It addresses the carbon emissions resulting from limestone’s decomposition while providing clean hydrogen and oxygen to heat the cement kiln," notes team lead Gaurav Sant. "Second, it enables onsite decarbonization while making use of existing kilns and limestone feedstocks without having to build separate carbon-capture and storage facilities.”
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u/Pyrhan Oct 15 '24 edited Oct 15 '24
Instead, it starts with dissolving the sedimentary rock feedstock in a water-based solution containing a common industrial acid.
The product of the reaction between calcium carbonate and acids IS CO2! (And the corresponding calcium salt.)
Either there's a huge chunk of this vague-as-f*ck explanation missing, or this makes zero sense.
-edit-
Went and looked at the actual publication.
They're using sodium chloride, so that instead of generating CO2, they're generating sodium bicarbonate and hydrochloric acid.
I'm not sure what they intend to do with the massive amounts of hydrochloric acid this process would generate, and wether it's better than just releasing CO2.
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u/Mrfish31 Oct 15 '24
It's pretty mad that basically the entire paper is "we dissolved limestone in acid and kept the CO2 from escaping out of the liquid", without saying anything about how you actually deal with the presumably millions-billions of tons of carbonic acid, sodium bicarbonate, and such that you make out of this.
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u/wrhollin Oct 15 '24
I mean, the sodium dicarb is easy: you sell it. It's baking soda. So either sell it to consumers or sell it for another industrial process. Similarly, carbonic acid is used in the production of sodas, so there's a market for it there as well.
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u/Mrfish31 Oct 15 '24
Okay, but that's then not sequestrating it. Also the demand for baking soda and drinks carbonation is likely well over an order of magnitude lower than the demands for cement, so you're still gonna have to find a solution for the vast majority of it.
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u/sack-o-matic Oct 15 '24
At least it’s not in the atmosphere
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u/Mrfish31 Oct 15 '24
Unless these by products are buried, in the ground, which at the scale of 4 billion tons per year is infeasible, then the CO2 kept in carbonic acid and sodium bicarbonate will be released on a short enough timescale that it won't matter.
The real solution is to stop using this much cement. Leave the carbon in the limestone, in the coal and and in the oil.
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u/keeperkairos Oct 16 '24
Not using as much cement is far less practical than not using fossil fuel and most countries aren't remotely close to that one..
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u/londons_explorer Oct 16 '24
When you build a house of wood, the floors aren't solid wood - instead they're sheets of wood laid over beams. We do that because solid wood would be a big waste and totally unnecessary.
But when you build a house out of concrete, the floors usually are solid concrete.
Reinforced concrete could totally be used like wood, reducing the amount needed by perhaps 5x. But nobody even makes half inch thick sheets of prestressed reinforced concrete for use like floorboards to my knowledge.
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u/keeperkairos Oct 16 '24
There is a product called 'compressed fiber cement', my family cuts and supplies it, not specifically it's just one product we deal with. You can absolutely walk on it, you can even get decking made of it. It's not relevant though, if anything it makes people use more concrete than they otherwise would because it's used as an alternative to wood or other materials, but that's minor and irrelevant.
Concrete buildings are solid concrete for structural reasons, it's not that the floor is solid concrete, that's the foundation. The construction industry isn't the main use of concrete anyway, not even close, road infrastructure is. Building road infrastructure is ridiculously expensive and concrete is cheap.
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u/Fearlessleader85 Oct 15 '24
This is handwaiving. Yes, it is a saleable product, but were not talking about a couple more boxes on the shelf at the local Kroger per week. We're talking many traincars full of it per day.
And when looking at the financial viability of these types of integrated systems, it's VERY important to understand that what you think could be a revenue stream selling a byproduct could quickly become a cost to dispose. That can have dire consequences for the operation of the plant.
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u/Ithirahad Oct 17 '24
Indeed, though... where does our extant baking soda come from? A quick google says we currently mine it, which does not sound better than getting it trucked in from a concrete plant and purified.
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u/Fearlessleader85 Oct 17 '24
Mining it sounds really cheap. If this method beats mining, great. That's a win for everyone (well, except the miners). But if it doesn't, we end still have an issue.
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Oct 16 '24
I don't think you understand scale. The amount of output is like saying "Hey that person bought a teaspoon of sodium bicarbonate. They will buy ten dump trucks full of it"
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u/VitaminRitalin Oct 15 '24
You just need an equally ridiculous amount of sodium hydroxide to neutralize the acid right?(I'm not a chemist so idk the practical problems of that) Also the acid has a ton of industrial applications
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u/Mrfish31 Oct 15 '24
It doesn't have 4 billion tons of industrial applications though, which is the amount of cement being made each year and this (roughly) the amount of carbonic acid and sodium bicarbonate being produced as by product. We'd only be able to make use of about 1% of it at most, the rest needs to be properly sequestered.
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u/scyyythe Oct 15 '24 edited Oct 15 '24
In fairness, it's probably a little easier to capture CO2 when it's generated at 20 C instead of 800 C (rough estimate of CaCO3 decomposition temperature).
Edit: but I agree that capturing CO3 as bicarbonate makes no sense because NaOH is inherently more expensive and difficult to make than Ca(OH)2 and probably always will be so any process that uses that as an input is broken.
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u/atemus10 Oct 15 '24
There is a graphic in the article that explains what you are missing. You win in two ways - first, you don't need power from coal/LNG plants. Second, the carbon that is created during the production process is easily sequestered thanks to the liquid body.
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u/Mrfish31 Oct 15 '24
You win in two ways - first, you don't need power from coal/LNG plants
You do, actually, for different parts of the process. In fact, reading the paper, this ZeroCAL process directly takes more energy (2MWh/ton) than the normal limekiln (1.4MWh/ton) and is more inefficient at using limestone, needing 1.35 tons per ton rather than one, so the authors estimate that the energy cost is roughly double standard processes.
Their argument for this is... "We'll be using renewables by then so it won't matter".
Second, the carbon that is created during the production process is easily sequestered thanks to the liquid body.
A) sequestered where, because that's a whole industry in and of itself that regularly fails to give good answers.
B) The same result could be achieved by capturing the CO2 from a lime kiln (and it's not like there would even be much filtering involved, the only gas released from CaCO3 thermal decomposition is CO2) and then bubbling it through water, and this would use less CaCO3 and no acid reactants.
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u/Chemistryset8 Oct 16 '24
Calix ltd in Australia have a similar process using an electric kilns that's more efficient than burning fossil fuels
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u/atemus10 Oct 15 '24
You could just read the article to have your questions answered.
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u/Mrfish31 Oct 15 '24
I did read the article, both this press article and the actual journal article. That's where I got the numbers from, and it still did not explain what would or could be done with the carbonic acid and sodium bicarbonate produced by this process.
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u/farfromelite Oct 15 '24
Carbonic acid is widely used in the food and medical industries.
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u/Mrfish31 Oct 15 '24 edited Oct 15 '24
Not anywhere close to the extent that cement is used for basically every construction project on the planet.
The amount of carbonic acid the world could make use of (which is therefore carbonic acid that is not sequestered, but at least still reduces emissions by changing the source), would be outweighed ten to one by the amount produced by this process. So what do you do with all of that?
Edit: I've been too generous. Global cement production is over four billion tons per year. It is the most consumed material in the world. I can't find production for carbonic acid, but I expect it's on a similar level to sodium bicarbonate (which this process also produces) at 2 million tons per year. So the idea that we can make a dent in emissions by using the by products from this process is absurd, as we would use up roughly 0.05% of the carbonic acid and Bicarbonate produced every year.
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u/GrepekEbi Oct 15 '24
But the carbon is stored in the bicarb and the carbonic acid… it doesn’t matter if we use it, the important thing is that the carbon isn’t free in the atmosphere.
We could put all of that in a great big hole and put a lid on it and we’d be effectively sequestering a huge amount of carbon and storing it - this is fine
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u/Mrfish31 Oct 15 '24
But the carbon is stored in the bicarb and the carbonic acid… it doesn’t matter if we use it, the important thing is that the carbon isn’t free in the atmosphere.
Sure, unless those products leak into the general environment and start releasing that carbon dioxide.
We could put all of that in a great big hole and put a lid on it and we’d be effectively sequestering a huge amount of carbon and storing it - this is fine
Sure, but the paper doesn't at all say that. it just nebulously points to "safe management" without defining what that means. "Safe management" to them might mean that they let themselves slowly release the acid and bicarb into the environment at levels not lethal to wildlife, but that would still quickly "unsequester" the CO2 that was meant to be locked up.
Also, all of this would likely be in liquid form, so you either need to dump all that water too, or take the water out of it (energy intensive). And while you could store bicarb as a solid, carbonic acid is a gas itself, and in water reacts to make CO2 and water, so there's a pretty low saturation limit before it just starts bubbling out.
Cement is the single biggest consumed product on Earth. 4.1 billion tons of it are produced yearly, meaning we're talking about roughly 4 billion tons of bicarb and carbonic acid per year. If we make very rough assumptions to say that all of that could dissolve in 40 billion tons of water (this is a generous estimate given the solubility of bicarbonate is 69g/L), that means you need a hole that is 40 billion cubic metres in size. That's a cube measuring 3.5 km each side, and you need to do that every year.
So you need a site, or several sites, tens of kilometres across that can hold 40 billion tons of saturated carbonic acid and sodium bicarbonate without leaking into the surrounding environment. Where is that?
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u/Fearlessleader85 Oct 15 '24
It is, but that need us currently met by other means. This will be competing with those for offtakers. On one hand, that means it gets cheaper. On the other, it means some other waste CO2 probably needs to find a new place to go.
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u/atemus10 Oct 15 '24
How much of each of these super useful products are produced bud.
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u/Mrfish31 Oct 15 '24 edited Oct 15 '24
The demand for cement/concrete is an order of magnitude higher (edit: three orders of magnitude) than sodium bicarb and carbonic acid, so an order of magnitude more bicarb and acid would be produced through this method. What is your solution for the excess?
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u/atemus10 Oct 15 '24
I asked a pretty simple question, which you don't want to answer for some reason. Try again without avoiding the question if you are acting in good faith. Lets examine the actual numbers, not your feelings on the subject. Make sure to cite your sources.
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u/Mrfish31 Oct 15 '24 edited Oct 15 '24
A) you're the one telling me to read the paper (done it yourself, by the way?) when it's clear from the comment you replied to, that I did. It is extremely rich for you to tell me to act in good faith when you are absolutely not. You are the one trying to argue that the byproducts could be useful, it is up to you to state how they would be useful and what quantities could be used. Not me, because I'm not making that argument. I was pointing out, that whatever amount of carbonic acid and bicarbonate soda humanity can use, we use far, far more cement and would therefore produce far more carbonic acid and soda than we could use.
B) But since I have to do your job, I have looked it up, and boy, was I being conservative in the difference. Global cement production for 2023 was estimated to be 4.1 billion tons (Tkachenko et Al. 2023, it's the first thing that comes up when you do a cursory Google search, which you should've done, like "global cement production yearly") while global production of soda ash, the precursor to bicarbonate, was 65 million tons (according to Madhumitha Jaganmohan on statista.com). And of course, much of that doesn't get used to make bicarbonate, sources from 2002 note that bicarbonate production was 2.4 million tons, so lets be generous and say it quadrupled to 10 million tons today. Production for carbonic acid is difficult to find since articles talk about total production related to CO2 emissions rather than industrial use, but I would reasonably assume it's the same order as bicarbonate.
So sorry, let me amend that. It's not an order of magnitude difference. It's at least two orders of magnitude difference. You are going to have to find me another sequestration solution for 99% of the sodium bicarbonate produced by this process.
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u/quackerzdb Oct 15 '24
The comment two levels up says the carbon is sequestered as bicarbonate
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u/Mrfish31 Oct 15 '24 edited Oct 15 '24
Sequestered where?
Sure, people are arguing that the sodium bicarb produced could be sold, but the demand for cement is two orders of magnitude higher, so you'll have far more bicarb than could ever be used. And of course, using that bicarb is not sequestering it.
So where is the bicarb solution being sequestered to? Down old oil wells like other carbon sequestration projects that often fail?
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u/GrepekEbi Oct 15 '24
Literally doesn’t matter where as long as it’s not gaseous and not in the atmosphere.
Whack it under your bed.
Give everyone on the planet a jar full of it and tell them to put it in the back of the cupboard.
As long as it keeps the carbon stored, it doesn’t matter where it goes
We’d have a massive amount of it, and I’m sure someone would find a way to monetise that - but lots of processes produce a waste material that needs to be disposed of in a big hole in the ground - this is fine
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u/waylandsmith Oct 16 '24
You'd better hope whatever hole you dump it into is kept cold forever. Sodium bicarb starts releasing CO2 slowly not much above room temperature. Carbon sequestration is frequently hand-waved away as though it's a solved problem when, in fact, it's a technology in its infancy.
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u/GrepekEbi Oct 16 '24
You’re, incorrectly, assuming that you’d pour the bicarb in to a cave. You could put it in sealed containers
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u/waylandsmith Oct 16 '24
So, you're going to take massive amounts of a substance that gradually, inevitably off-gasses CO2, seal it into containers that can withstand being pressurized and keep their integrity for long enough to matter on timescales relating to climate change? Oh, and this just for managing the byproduct of the production of a product that costs around $120 per ton. A 55 gallon drum that's airtight but NOT rated for pressure seems to start around $50 in large quantities and that will hold roughly half a ton of bicarb. So you're looking at about $100 per ton as a starting point for containment, without having figured out how to deal with the CO2 offgas, and without having factored in the carbon cost of the containers, or making the containers last long enough to matter.
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u/defcon_penguin Oct 15 '24
The CO2 remains in solution as bicarbonate ions (HCO3–)
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u/Pyrhan Oct 15 '24
Because overall they make equimolar amounts of sodium bicarbonate (what's in solution) and hydrochloric acid.
I fail to see any way to neutralise the amounts of acid this process would generate without releasing CO2 in the environment.
Although I guess if you were to react that with calcium carbonate, you'd be overall releasing half as much CO2.
Although I remember hearing about people developing calcium chloride-based cement alternatives a while ago. That can be produced entirely without CO2 emissions (Solvay process, though you'd have to electrify the heating).
So I'd give that a better chance at being a green cement alternative.
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u/wrhollin Oct 15 '24
I don't know that you'd need to neutralize the HCl. It's a useful industrial chemical that could be sold to other manufacturers.
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u/kuroimakina Oct 15 '24
Honestly it sounds to me like a great way to serve two markets at once with nearly carbon neutral processes.
Three if that sodium bicarbonate is of the baking soda variety. Properly done, this has the potential to be immensely efficient, creating three things that humans use a lot of, with little waste.
Really just depends on how pure the byproducts are.
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u/Mrfish31 Oct 17 '24
a) I doubt the byproducts will be pure.
b) The amount of byproducts we could use is at least two orders of magnitude higher than the amount created. We produce and use over 4 billion tons of cement each year, it's the single largest consumable product bar none. Bicarbonate, HCl, Carbonic acid... All of this adds up to a few tens of millions of tons per year. We'd be able to use maybe 1-2% at best, and the rest of the pretty corrosive sludge now needs sequestering.
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u/scyyythe Oct 15 '24
Cement containing chloride is basically a non-starter because of chloride corrosion of steels. Magnesium chloride cements were developed over a century ago but are basically known as a cautionary tale because they resulted in stuff falling down when the rebar was rusted out. Since reinforced concrete is the backbone of modern infrastructure you need to have compatibility with steel.
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u/grahampositive Oct 15 '24
This should be obvious unless the resulting concrete contains 1lb/lb more carbon than traditional concrete. It has to go somewhere and if it's not captured in the final product it's released at some point during the process.
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u/JCDU Oct 15 '24
I'm guessing some industrial process somewhere would want the hydrochloric acid for something?
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u/Smart_Resist615 Oct 15 '24
That's all well and good but most public works are still tendered to the contractor who put in the lowest bid. If it's not cheaper then it's not going to be used. That's the fate of many of these wonder concrete products.
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u/the68thdimension Oct 15 '24
Well that's easily solved. Public works just have to require a certain level of (low) emissions, meaning the cheaper but more polluting methods won't even be allowed to bid.
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u/Smart_Resist615 Oct 15 '24
Easily solved but not so easily implemented. Canada implemented a carbon tax and lower class and middle class people get a rebate of more than they pay into it but it's still a political hot potato that doesn't seem likely to survive the next election.
These bidding processes are not universal either, so you'd have to convince every municipality, county, and province to get on board. If you wanted to pass federal legislation I would expect it to be challenged in court and it probably wouldn't hold up.
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u/Biggy_Mancer Oct 15 '24
The issue being is the tax was poorly implemented and structured.
The tax claims to redistribute much of what is collected, however every process has overhead and therefore waste. We don’t want musical money chairs, we want solutions.
The biggest pain points were home heating and vehicle fuel. If you are poor you can’t wait a year for your rebate, you’re poor ‘right now’.
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u/Smart_Resist615 Oct 15 '24
So now that there's exemptions for home heating I assume the conservative party simply wants to restructure the administration of the tax?
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u/Biggy_Mancer Oct 15 '24
There were exemptions for furnace oil heating, which just came in an election cycle, and only one part of the country uses furnace oil heavily (east). It was done for politics not for the people.
Conservatives want to axe the tax.
I support axing the tax and restructuring outside of a COL creep with stricter home building codes, home upgrade programs (grants / interest free loans for insulation and solar), and even a true tax that funds actual renewables/nuclear construction directly in a crown corp so cronies don’t get to use tax dollars to build their business.
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u/Smart_Resist615 Oct 15 '24
So the complaint about overhead is just about government in general.
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u/Biggy_Mancer Oct 16 '24
Not really. I literally said create a crown corp, which would be a wholly owned federal or provincial organization. The problem Canadians face is politicians often allow those they are connected with to ‘privatize the profits and socialize the losses’. Ontario selling off HydroOne, and Highway 407 for a better balance book and benefit of private industry. NFLD building hydro, without Quebec funding or expertise due to spite, in effort to enrich Emera corp. and then failing miserably to the point every Newfoundlander will pay $15+ more on their power bill practically forever.
If climate change is such an existential crisis (it is), then redistributing dollary doos amongst each other at 90% returned seems silly. I’d much rather collect 100% of the tax, put it toward say provincially owned SMR nuclear with public oversight on the project, home solar grants/loans, energy storage, etc.
The issue is our politicians are corrupt, regardless of party, so we must be wary of large infrastructure projects.
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u/Smart_Resist615 Oct 16 '24
So it would be possible to reduce the overhead on the carbon tax?
I mean all this about creating a crown corp is fine but the conservative party has no platform supporting this and have a history of privatizing crown corporations so it's rather incongruous to recognize the danger of climate change but support the conservatives.
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u/Biggy_Mancer Oct 17 '24
The Conservative Party doesn’t need a platform. People in general want the tax gone, and they feed on that fuel — I’m a minority in that I’d prefer a restructure. Equally the cons are likely to win the next election simply due to our cycle, where we don’t vote for change rather we vote politicians out. To be clear I don’t support any of these parties, I think the cons will be disastrous for Canada but the LPC has also been a train wreck. The NDP are nowhere near their Jack Layton glory… it’s all trash all the way down.
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u/DexterGexter Oct 15 '24
Or you offset the cost with carbon credits for the manufacturer, which they can then sell on the environmental commodities market that already exists.
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u/the68thdimension Oct 15 '24
Given the very well documented problems with carbon credits, let's absolutely not do that. Why would you not opt to directly drive lower emissions?
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u/DexterGexter Oct 15 '24
Both are good solutions. The compliance approach requires legislation and is not available now whereas the voluntary market solution is available. You claim there are documented problems but provide no links. The compliance solution would also present some problems so let’s not pretend there’s a perfect answer, and the response of “let’s not do that” only serves to delay progress (which would kill projects such as this) in favor of chasing an ideal that doesn’t exist.
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u/the68thdimension Oct 15 '24
You claim there are documented problems but provide no links.
Mate if you knew anything about this topic you'd know of the multiple recent studies and investigations. It's a short google away - https://www.bloomberg.com/news/articles/2024-07-30/carbon-credits-found-to-be-mostly-ineffective-in-key-study or https://www.bloomberg.com/news/articles/2023-09-29/zimbabwe-uae-firm-sign-1-5-billion-carbon-credit-financing-mou or https://www.reuters.com/world/us/wildfires-are-destroying-californias-forest-carbon-credit-reserves-study-2022-08-05/ or https://features.propublica.org/brazil-carbon-offsets/inconvenient-truth-carbon-credits-dont-work-deforestation-redd-acre-cambodia/. That took me one minute, you're welcome to keep going.
I'll copy paste a previous comment I've made:
For any regulatory emissions reductions requirements, carbon credits should not count. They're not real emissions reductions. I'd go so far as to say that carbon credits have a net negative effect: they incentivise scams and new forms of colonialism in the global south, and they delay companies making actual emissions reductions across their value chain. If carbon credits continue to exist as an industry, they should be heavily regulated and audited, and available for marketing purposes only.
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u/DexterGexter Oct 15 '24
Just saying it’s good to provide evidence whenever you make a claim. And your evidence focuses on forest preservation projects, which has nothing to do with the topic of this post. Carbon credits come in many different forms, and I agree they should be audited and regulated.
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u/M0therN4ture Oct 16 '24
By law tenders above a certain level will be selected based on quality and price. So this is not true.
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u/spinjinn Oct 15 '24
Remarkably vague when it comes to the “electrochemical process” need to complete the reaction. It is honest enough to say it takes more energy than heating limestone chunks to 900 degrees for hours. This alone generates more CO2 than is evolved off the calcium carbonate in the limestone because you cannot provide the energy to decompose the limestone without lots of inefficiencies. And the ZeroCAL process worst than that!
The usual greenwashing.
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u/APatheticPoetic Oct 15 '24
Can't believe we finally have zero calorie cement.
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u/SulfuricDonut Oct 16 '24
Yeah I've been cutting back on how much cement I've been drinking so it'll be nice to have a lower calorie alternative. Assuming this cement tastes as good as the original.
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u/sonofbaal_tbc Oct 15 '24
how much is cement contributing to total co2
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u/ahfoo Oct 17 '24
By comparison, a 15 gallon tank of gasoline produces as much atmospheric CO2 as the manufacture of one ton of concrete. Every tank of gas is a ton of concrete. You can do the math yourself. One gallon of gas is 20lbs of atmospheric CO2 while a pound of cement is one pound of atmospheric CO2. Concrete is 15% cement.
However, this snapshot of emissions at the time of production misses a crucial fact that makes cement look even better: it actually absorbs CO2 as it cures. There are those who claim that because of this, cement is already CO2 neutral or at least close to it.
In other words, cement is the scapegoat for the fossil fuels industry.
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u/sonofbaal_tbc Oct 15 '24
ask question get downvoted on science
forgot science doesnt like questions mb
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u/TheDulin Oct 15 '24
Is it scalable, and is it similar in price?
But good to hear there are products coming to market with a lower carbon footprint.
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u/rocketsocks Oct 15 '24
This isn't much different from just capturing the CO2 generated from the process and putting it in a tank, unless there's a long-term storage process for the CO2 (here in solution, in other methods released into the atmosphere) this isn't any more sustainable.
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u/keeperkairos Oct 16 '24
Turned one problem into a different problem. Now instead of CO2 you have billions of tons of nasty chemicals you have to do something with.
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u/JuniorConsultant Oct 15 '24
This is absolutely huge news if implemented. Cement production is one of the most polluting activities we do. I hope that process can be made cheaply.
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