Scientists Strengthen Concrete By 30 Percent With Used Coffee Grounds (engadget.com) 84
According to a team of researchers from RMIT University in Australia, coffee grounds can be used as a silica substitute in the concrete production process to yield a significantly stronger chemical bond than sand alone. Engadget reports: "The disposal of organic waste poses an environmental challenge as it emits large amounts of greenhouse gases including methane and carbon dioxide, which contribute to climate change," lead author of the study, Dr Rajeev Roychand of RMIT's School of Engineering, said in a recent release. He notes that Australia alone produces 75 million kilograms of used coffee grounds each year, most of which ends up in landfills. Coffee grounds can't simply be mixed in raw with standard concrete as they won't bind with the other materials due to their organic content, Dr. Roychand explained. In order to make the grounds more compatible, the team experimented with pyrolyzing the materials at 350 and 500 degrees C, then substituting them in for sand in 5, 10, 15 and 20 percentages (by volume) for standard concrete mixtures.
The team found that at 350 degrees is perfect temperature, producing a "29.3 percent enhancement in the compressive strength of the composite concrete blended with coffee biochar," per the team's study, published in the September issue of Journal of Cleaner Production. "In addition to reducing emissions and making a stronger concrete, we're reducing the impact of continuous mining of natural resources like sand," Dr. Roychand said.
The team found that at 350 degrees is perfect temperature, producing a "29.3 percent enhancement in the compressive strength of the composite concrete blended with coffee biochar," per the team's study, published in the September issue of Journal of Cleaner Production. "In addition to reducing emissions and making a stronger concrete, we're reducing the impact of continuous mining of natural resources like sand," Dr. Roychand said.
What about tea leaves? (Score:4, Interesting)
Is there something unique to coffee or will other organics, such as tea leaves, work just as well?
Re:What about tea leaves? (Score:4, Insightful)
Coconut and walnut shells will probably work like coffee beans.
My main concern, when I read about innovative concrete recipes, is "how will this scale?". I haven't looked up the numbers, but I have the feeling that concrete and coffee production operate on vastly different material quantity levels.
Re:What about tea leaves? (Score:5, Informative)
My main concern, when I read about innovative concrete recipes, is "how will this scale?". I haven't looked up the numbers, but I have the feeling that concrete and coffee production operate on vastly different material quantity levels.
I took a cursory glance at the numbers and one paper suggests SCGs (spent coffee grounds) from industrial sources alone (the only sources we can reasonably expect to capture, without significant additional infrastructure) total about 6 million tons per year. [mdpi.com] But that's a weight for wet coffee grounds, which are approximately 40% water [mcgill.ca], so call it 3.6 million tons of actual coffee grounds. This should be removed before transport, to reduce costs, so some additional infrastructure will probably be required at the source (instant coffee and coffee concentrate manufacturing plants.)
Every year we use roughly eight billion tons [theworld.org] of sand to make concrete. Consequently, we could only reasonably enhance a very small percentage of concrete with biochar made from coffee grounds, at best. Still, there's no good reason NOT to do so. Direct solar thermal pyrolyzation could be used both to drive out the water (with relatively little collector area) and to perform the final process of conversion into biochar, and this seems like the only significant infrastructure requirement.
Re:What about tea leaves? (Score:4, Funny)
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Heating to 350C you'd likely have much of the original material burn off as well, I wouldn't be surprised if that drops it another 20-30%.
Though I'd be surprised if there was anything special about coffee in this application, the result is really just carbon. Someone mentioned tea leaves likely reducing to strings, if anything that seems like it would add strength and used textiles is another possibility. It could even be the case that it is worthwhile to utilize fast growing and renewable organics like bam
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I could believe that the physical structure of the coffee grounds was beneficial in some way related to processing. Which then makes me wonder if they would be a good source of carbon filter material, like coco coir.
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I have a suspicion that coffee grounds are far more expensive than sand. I don't want anyone mining my compost heap either.
Re:What about tea leaves? (Score:5, Interesting)
Actual paper on the topic [semanticscholar.org].
I'm no expert in concrete, though I read up on it some in college. Also seen a lot of "Here's how we can make concrete better!" articles.
Basically, mixing good concrete is actually pretty tough, and there are so many variables that just making some using your proposed ingredients and testing it is the only way a lot of the time. Even the sand can vary and alter the strength.
In general, sand's big advantage in concrete is that it is cheap and doesn't decompose. That's it. Even the grade of sand matters. For example, ocean sand is, even rinsed of salt, horrible. It's too worn down. Sand from mountain streams is better. Even better than that is mechanically crushed rock - but that is more expensive. It's basically more microscopic shards are better, and ocean sand has too many of those worn away. Some fraud involving ocean sand is how a couple buildings in China collapsed, I remember reading. Supplier substituted ocean sand for river sand, resulting supports weren't strong enough, building goes down(fortunately) during construction and didn't kill anybody(the workers saw the signs soon enough to get away).
Then you have that there's a huge amount of stuff you can add to concrete to make it "better", IE stronger or whatever. Iron/Steel rebar is the most commonly used, but you can also do fiberglass - including what are basically just fiberglass whiskers poured into the mix. They help prevent cracking.
In this case, it specifies that they "pyrolyze" the coffee beans first. What this means is that they're basically reducing the grounds to charcoal. You heat it up to 350-500C(660-932F) in an oxygenless environment. This will cause all the volatile chemicals to off gas. Not exactly charcoal because it's coffee grounds rather than wood, but the same sort of process. And found another article, yep, they reduce it to "biochar". [rmit.edu.au] Looking up biochar in concrete, it might be useful for building offices and apartment buildings out of, because the concrete is lighter and more sound absorbing. Ergo, fewer complaints about neighbors. But it also specifies that the concrete has less strength [sciencedirect.com]. So this concrete being stronger? So much stronger? That's iffy.
But you're still baking your coffee grounds for at least a few hours, so you have to create an oven, clear out the O2, heat to that temperature, do intermittent processing, etc... It's going to be a fairly pricy process. Even if you can get the grounds for free - say, from an instant or canned coffee factory, the processing will be the expensive part.
Remember me mentioning that freshly ground stone is actually a very good aggregate material? That's a 14% boost in strength [sciencedirect.com].
So it sounds like it's possible, but there's more to concrete than just strength - How well does the resulting concrete weather/age, for example? That bit might take a decade or two to test.
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Well, you're never going to get organic, but "ethically sourced" is totally a thing. It's actually become a problem because of China's building boom. They like building with concrete a lot more than the USA(we use more wood), such that getting enough of the correct grades of sand have become a problem. Ergo shit like selling ocean sand. You also can't take too much river sand - otherwise you make the river too big, etc...
Crushed rock is superior and sustainable. In the sense that we're not going to run
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Sand from streams is rounded by abrasion, so there are fewer sharp angles for cement to grip, so crushed rock works better.
Adding fiber also helps strengthen concrete. Coconut fiber is used in some countries. It prevents cracking and makes the concrete more shock-resistant. It can also improve acoustical damping.
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Yeah, I mentioned that crushed rock works better a couple times, and yes, it's basically because of microscopic sharp angles. As you move closer to the ocean, those get ground down and you end up with sand that is finer and finer, closer to microscopic spheres. You want nice big sharp particles for good concrete.
But river sand is usually good enough and cheaper...
The fibers I'm familiar with are fiberglass ones, and as I mentioned in my first post in this tree, it helps prevent cracking. Wasn't aware of
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Great comment, thanks.
This is interesting research but surely the pyrolization generally produces far more C02 than composting, so that part is effectively bunk.
Once a paper starts with a half-truth it's hard to justify trusting my next deck pier to its conclusions.
Probably a public-money-ruins-science-again artifact to meet a grant, but still.
Pyrolizing [Re:What about tea leaves?] (Score:4, Informative)
Great comment, thanks.
This is interesting research but surely the pyrolization generally produces far more C02 than composting, so that part is effectively bunk.
Not.
Pyrolyzing requires heating in the absence of oxygen, so it doesn't produce oxides of carbon, it produces just carbon.
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Presumably they're referring to the source of energy used to produce the heat, not the pyrolysis itself. But then that depends on the source of the energy.
Re: What about tea leaves? (Score:2)
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"This is interesting research but surely the pyrolization generally produces far more C02 than composting"
Not necessarily because that carbon doesn't stay in the compost over the long run and the output of this process basically is the carbon when then gets locked up in the concrete.
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Coffee grounds hit the reuse element but I wonder if growing some other organic material at scale for use in this process would be a better plan. Instead of tearing up the ground mining silica [which there is plenty of] we pull carbon out of the air rapidly growing organics and then lock that carbon up construction.
That might be more scalable for industrial demand and drastically cut the added negative impact of transporting coffee grounds from wherever they are used to where concrete is needed and mixed be
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I doubt that Keureg pods would ever hit the critical threshold for being "worth it", recycling wise for something like this.
Ironically enough, the Folgers Crystals factor would be the first spot I'd head for lots of coffee grounds.
I'd see a processing center pop up adjacent to something like a instant or canned coffee factory first - industrial brewing, industrial amounts of used grounds.
After that, maybe recycling from coffee shops and restaurants. You can ge a minor pile from a McDonalds that brews a big
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Is there something unique to coffee or will other organics, such as tea leaves, work just as well?
Since they first step is reducing it to char, I'd think pretty much any plant material would work equally well
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I don't see any reason for any organic material to "Strengthen" concrete, After it decays after a few months, it would leave voids in the surface, allowing easier ingress of rain.
That said, this is also not the first time and organic material has been used to strengthen concrete. Coconut fiber and Bamboo have also been used. Coconut replaces silica, bamboo replaces rebar. You also can't just dump this material straight into it, it has to be treated so it adheres.
This is why I suspect the story isn't as simp
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My thought is also that bulking a batch of concrete with carbon chunks made from charred biomatter is essentially the same as concrete with air bubbles. Maybe we should be looking into other things that result in making a sponge structure in the concrete.
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Although it doesn't make a sponge structure, volcanic dust in concrete strengthens it enormously when you mix the concrete with sea water. The sea water and volcanic ash react generating (a) a fair bit of heat, and (b) large crystals that act like rebar, only they're completely chemically stable. I suppose these crystals could be considered bubbles of a sort, just not air bubbles.
climate change? (Score:1)
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Actually, this would be "one of those projects" that are done by a professor and a handful of graduate students who are currently lacking any major funding to get something under their name published.
Consider, the coffee grounds can come from their own personal pots, they specify "used" for a reason.
A 94 pound bag of portland cement runs $20.
Concrete sand is $7/50 pounds.
So for ~$50 you get enough material to do a bunch of testing. Concrete is typically 1 part cement to 2 parts sand and 4 parts larger aggr
not relevant (Score:5, Insightful)
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... ground coffee is not produced in industrial scale facilities ...
Tell that to all of the industrial producers of instant coffee. I'm sure they will be quite surprised!
Re:not relevant (Score:4)
I noted the producers of instant and canned coffee as possible sources for this, thinking of the hassles of collection from small scale sources.
Still, that raises the question - what proportion of coffee is used by industrial sources, compared to locally brewed? I'm not a coffee drinker myself, I know that my dad(the only drinker I'm familiar with) has both instant coffee and a small grinder in the house.
So I did some searching. almost 50% [beanground.com] prefer instant coffee, surprisingly enough. I must be around a bunch of coffee snobs then, because I'd have guessed it to be much lower. That said, my brother also drinks coffee - but only store bought fresh stuff. Think brewed coffee from gas stations and fast food joints. Maybe a starbucks occasionally. But those are all "freshly" brewed. I'm also getting $30B [statista.com] for the instant coffee market, $88B [statista.com] for coffee in general. Given that instant coffee tends to be cheaper, but also probably more efficient in beans? I'd say that expecting 30-50% of beans to be used in factory conditions would be a reasonable estimate.
And from my time working in a McDonalds, decades ago, you'd be lucky to get a kitchen garbage bag's worth of grounds (~40 Liters?) in a day. It'd also be a wet hot mess, so mold and such would probably be a concern. A lot of resources needed to collect that stuff up specifically. Before you go baking it into biochar(non-wood charcoal, basically).
I think university students like studying coffee grounds because it's a locally generated resource for them in quantities sufficient to test with.
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And yes, lots of people do instant coffee. When you need something to wake up to, it's literally instant coffee and hot water. The fancy coffee drinks from the shop or other stuff can come later. Unless there are people who can work a cappuccino maker first thing in the morning but can't do anything else?
Go old school - drip machine. Put in filter and coffee grounds, possibly the night before, add water and maybe hit a button in the morning. No cappuccino maker needed. Still generates used grounds though.
I wouldn't rate restaurants as "industrial" - industrial would be the sites making instant coffee and such. And like I said, the amount of coffee grounds even in a McD's is fairly limited, compared to the volume you'd see with industrial concrete. Not sure a separate truck would be worth it.
Hell, you m
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Go old school - drip machine. Put in filter and coffee grounds, possibly the night before, add water and maybe hit a button in the morning. No cappuccino maker needed. Still generates used grounds though.
I make drip coffee in the morning, then I drive right past a drive through coffee shop where people are paying ten times more per cup than I'm paying per pot. I haven't bothered to try their coffee since I hear it's terrible. The only person I know who goes to that shop gets infused red bull there, not coffee. What a world.
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That is a drastically different industry size though. Look how much coffee is in your home and then look at the amount of concrete used in your street, foundation, fence posts, etc. Then consider those coffee grounds are 40% water and probably reduce another 20-30% in that heating process.
Based on numbers someone found above used coffee grounds [total] won't put a very significant dent in replacing the sand used for concrete. But I doubt there is anything magic about coffee grounds here. Hemp or Bamboo migh
Re: not relevant (Score:2)
Ground coffee is also produced in industrial locations. That's the buy-product of soluble coffee production. I know of at least one soluble coffee factory in Australia.
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They compare to standard concrete while several higher strength concretes even way beyond their performance is available. So it is all about price or sustainability they could improve.
Standard concrete is where the biggest bang for your buck is.
And ground coffee is not available on any relevant scale. They used the unusal 75 mio kg notion instead of 75 000 t and missed to give that australias concrete production is 29 mio m ~ 70 t as reference, so even in most optimistic collection scenarios less than 1% could benefit from their research. Not to mention that ground coffee is not produced in industrial scale facilities but at home, offices and coffee shops: All small scale places and therefore high effort to establish collection. Transport will ruin even any remaining sustainability claim.
In principal 100% of SCG could be used, in practice it's not really feasible.
But that doesn't mean irrelevant.
I don't know how all those coffee pods get recycled, but if that's an automated process that's another potential source of SCG.
And I don't know about the cost of sand, but it may turn out feasible to buy back the coffee ground from restaurants, which again could scale it up.
And SCG are probably not the only good source of concrete enhancin
Cost of sand (Score:2)
For the cost of sand, from a hardware/home supply store, it's $7/50 pounds.
If you want a truck full of the stuff, it's $300-700 per dump truck full, or $15-50 per cubic yard, and a cubic yard is 2600-3200 pounds, or 1.3-1.6 tons.
If sand is still an option, you're probably not going to see companies buying used coffee grounds for anything at all, because they're like 40% water by weight(unless the site is running them through some sort of dehydration process), then after you dry them out you need to bake the
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"Transport will ruin even any remaining sustainability claim."
I'm assuming we already have to transport the waste coffee grounds someplace (to a landfill, or composting site).
There may be some added cost for using a unique transport, that would be a partial loss to total sustainability.
And perhaps all the new infrastructure needed would end up in a total loss.
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I'm assuming we already have to transport the waste coffee grounds someplace (to a landfill, or composting site).
Coffee grounds are going to be a rounding error for most trash collection vehicles. I'm not sure you'd see any fuel savings from the reduced weight, and having a separate vehicle collecting the grounds would be all new fuel use.
It's like how many recycling collection programs are actually net negative for the environment over just throwing the recyclable products away, because of the extra fuel use in sending a big dirty diesel to pick everything up, stopping every hundred feet or so.
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i was assuming industrial scale, not residential.
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Ah, that makes sense. But from my limited research, you might be able to get 30-50% of the total stream if you concentrate just on industrial sources - basically instant and canned coffee manufacturers.
You can also expect more processing, such as drying, from an industrial producer, which would drop weight considerably.
Though that does bring to mind that if you're drying the stuff out, you might be able to reduce it to biochar in the same step - even less to transport to the concrete plant.
Pyrolyzing (Score:3)
No (Score:2)
Look up how charcoal is made. The process releases more than enough flammable gases which are used to heat the kiln. It is essentially an incomplete burning.
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They used a coffee powered plant, they burned coffee to burn their coffee. You get double the pyrolized coffee that way, it's double green aka green green.
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In this case, probably an electric oven - easier to control temperatures.
As Wdi mentioned, in an industrial process, they'd probably use the gasses generated by the charing grounds to fuel the process. Making at least that part carbon-neutral, especially given that carbon is what's mostly left afterwards.
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Check my math (Score:4, Insightful)
The article begins,
"Humans produce around 4.4 billion tons of concrete every year. That process consumes around 8 billion tons of sand ..."
Are we to assume that somehow billions of tons of sand are 'consumed' during the process, never to reappear?
And I agree with the other poster: while this might make an interesting doctoral thesis, I can't see how collecting coffee grounds on that kind of scale could consume less energy than using sand.
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A google search would indicate this has already occurred.
No, seriously.
https://www.bbc.com/future/art... [bbc.com]
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https://www.bbc.com/future/art... [bbc.com]
tldr: not all sand is the suitable and worldwide consumption is up (China, mostly).
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Sheesh. Editors.
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Are we to assume that somehow billions of tons of sand are 'consumed' during the process, never to reappear?
It only reappears when the concrete is recycled, and generally not as a pure sand product again. It's reused as "aggregate" which is a different component in concrete from the sand. Both are required for the "best" concrete.
It's still going to be out of the system for the next 40-100 years, on average.
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About half the sand mined for concrete is not of the proper grade for it, and gets used for other things. When the sand particles are too round, they make poor concrete.
The same basic issue exists with biochar. You can make biochar out of any organic, however, you face the same rounding issue. Coffee grounds produce fairly uniform biochar with the sharp edges needed for the mechanical interlocking that gives concrete its strength.
There is some work being done on hot mixing coffee ground biochar in concr
What? (Score:3)
Help the planet by removing nutrients and putting them in concrete?
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We're not exactly short of anything left over in the biochar - that's mostly just carbon.
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We are sealing them in for freshness.
Controlled environment (Score:2)
Anecdote. Where I live, environmentalists pushed municipality to mandate mulched tire additions into asphalt. This resulted in asphalt pavement failure in just a year, when regularly it would last here almost a decade. So now we have a number of roads tha
Going to coffee shop to do my part for production (Score:2)
Have they tried spinach? (Score:1)
It works for Pop-Eye.
Wake up (Score:4, Funny)
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Finally I'll get to work on time.
Natural carbon cycle (Score:2)
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By now nobody should have to tell you that as an element, carbon is fungible. It doesn't matter if we emit carbon from oil and then fix carbon currently held in SCG, what matters is whether we maintain a balance. Doing this clearly would not restore the balance, but it might be one of many strategies that help form a complete solution.
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If they are landfilled, very likely true, the decomposition is anaerobic.
If they are used as compost, probably not. They are usually used as top dressing, not turned in while fresh. They are especially beneficial for roses...
Burn the fertilizer? (Score:2)
"Coffee grounds contain approximately 2 percent nitrogen, 0.06 percent phosphorus, and 0.6 percent potassium by volume. They also contain many micronutrients including calcium, magnesium, boron, copper, iron, and zinc."
https://www.uwyo.edu/barnbacky... [uwyo.edu]
It would make far more sense to haul the grounds to a farm than to calcine them into a concrete additive.
Coffee grinds are plentiful and mediocre fertilize (Score:2)
It would make far more sense to haul the grounds to a farm than to calcine them into a concrete additive.
There are many better fertilizers. If this improves concrete by 30%, I can see many scenarios where the coffee grounds are more useful as an industrial additive.
I've been gardening with used coffee grounds for 10+ years. I'm a coffee fanatic and like recycling my food waste. I honestly have never noticed the difference between soil with any degree of coffee grounds. I go through a pound of coffee in a week or 2. By Spring, I have probably 50lbs of composted coffee grounds to work with and I have tri
The best part of building up, (Score:1)
Isn't this just ash? (Score:2)
Isn't this just ash from burning up the coffee grounds? They are already mixing ash into concrete.
I think this is more of a "sustainability" project, but it's not going anywhere. Nobody is going to set up the infrastructure to gather up and process coffee grounds at any useful scale. Concrete makers produce specific mixes with characteristics for specific applications. They won't use this unless they can be assured of a reliable and cost-effective supply with consistent properties.
A more interesting and p
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Isn't this just ash from burning up the coffee grounds? They are already mixing ash into concrete.
No, not ash-- char.
Ash would be if you burn it in air; char is what you get if you pyrolize it without air.
(ash tends to be a bit basic, since it's the oxides left after the gaseous oxides go away. Might work for cement, for that matter, since cements use alkali, but too much alkali makes cement weak).
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Isn't this just ash from burning up the coffee grounds? They are already mixing ash into concrete.
No, not ash-- char.
Ash would be if you burn it in air; char is what you get if you pyrolize it without air.
(ash tends to be a bit basic, since it's the oxides left after the gaseous oxides go away. Might work for cement, for that matter, since cements use alkali, but too much alkali makes cement weak).
Interesting, didn't make the distinction between ash and char.
Info from the DOT on the use of fly ash in cement: https://www.fhwa.dot.gov/pavem... [dot.gov]
Carbon (Score:1)
I guess the industry is bound ... (Score:2)
...for a big brew-haha.
And now? (Score:2)
Call the plumber (Score:1)
Exchanging one kind of emission for another? (Score:2)
The disposal of organic waste poses an environmental challenge as it emits large amounts of greenhouse gases including methane and carbon dioxide, which contribute to climate change
So we replace the emissions from composting, with emissions from making concrete? Concrete making accounts for about 8% of all greenhouse gas emissions worldwide. https://www.cbsnews.com/news/c... [cbsnews.com]. So how have we gained something here?