Some way to use up recycled glass cullet has potential. There's a glut of that.
We'd have to see a fuller lifecycle analysis of a variety of construction scenarios.
We need new materials here urgently. Ideally something which, like plants, would pull the carbon from the air during the curing process. Whoever creates such a material is going to get very very rich..
The C in that would be the carbon sequestration. :)
For example, "the wall". Obviously advocates of the wall for the most part don't give a crap about the environmental impact. But even on the Left I don't hear this cited often as a reason to oppose it (amongst many). The CO2 emissions from constructing a several hundred mile long concrete or steel border would be enormous. (Steel is also a major emissions source.)
Even urbanists, who generally talk a lot about denser construction as having environmental benefits and are kind of "lefty", don't generally talk about the counterposing cost of concrete & steel emissions. I'm not saying it doesn't pencil out, but let's please always talk about it.
You probably don't hear this approach taken very often because most people won't consider it persuasive when they remember that we have nearly 50,000 miles of interstate highway and many many times more miles of lesser highways and roads. The concrete and steel needed for a couple hundred miles of wall would be a drop in the bucket of infrastructural concrete and steel across the country.
You can of course argue that every drop counts, but that sort of argument isn't going to impress many people, which explains why you don't hear it very often. Arguments against the necessity of the wall have more bite.
This might still be worth if it prevents illegal migration of 1 million people per year from countries with much lower CO2 emissions per capita (e.g. Venezuela 6t/year) to the USA (16.5 tons/year).
http://greennews.ie/carbon-footprint-of-trumps-proposed-us-m... estimates the carbon footprint of the „Wall“ as 48m tons - once. With my simplistic numbers above it saves up to 10.5m additional tons per year (i.e. N times that amount in N years). So its carbon footprint is amortized in less than 3 years.
That said, I have no political opinion about the „Wall“ (being in Europe), I just like analyzing both sides‘ arguments.
> The estimated CO2 emissions of the average immigrant (legal or illegal) in the United States are 18 percent less than those of the average native-born American.
> However, immigrants in the United States produce an estimated four times more CO2 in the United States as they would have in their countries of origin.
So I suppose the overall logic still holds, just slightly adjusts the math.
A while ago at dinner a friend said she was trying to do the right thing environmentally, but it was just too complex. (The case in point was her wanting an EV but hearing that while the car would be clean, there would still be emissions back at the power plant producing the electricity - true in many places but not in my country which has around 78% renewable grid energy).
Your comment clarifies just how very complex it is understanding the overall impact on the environment of our actions.
(No comment on whether a wall would actually prevent 1M illegal migrants a year).
That is absolutely absurd as only 190K/year cross that border illegally to begin with. Most undocumented immigrants in the US enter legally and just overstay their visas.
1. It assumes that each immigrant’s carbon footprint will suddenly leap to typical American consumer levels. But desperately poor immigrants are likely the lowest producers of emissions. Thus, admitting more would actually lower America’s per capita carbon footprint.
2. Addendum: This "1M/year kept from entering" hypothetical is utterly ridiculous to begin with. Even if the wall was 100% effective -- which is absurd given it can be climbed over with a ladder or tunneled under -- only 190K/year cross that border illegally to begin with.
And what is absurd about an unguarded wall being very ineffectual? As an obstacle it represents a rather modest practical challenge compared to walking the length of Mexico for example. A tall enough ladder isn't a very exotic object, and rudimentary training of its handling will be provided by the same people who teach how to cross the desert.
So putting up a wall on some parts of the border makes it not worth the the effort and risk of crossing at those parts, but if you put it up all over the border you only modestly increase the total risk.
Not saying sprawl doesn’t have its own impacts, just that we should properly account for the footprint of concrete and steel construction.
Many of the densest neighborhoods in the world have no buildings taller than 5 or 6 stories.
But I would be surprised if a 40-story apartment building and the infrastructure to service it required more concrete than housing the same number of people in a low-density suburb. Consider all of the sidewalks, sewers, parking lots, concrete foundations, elevated highways, bridges, .... involved in building and servicing a low-density car-commuter neighborhood.
You make good points about sidewalks etc. but at the same time that stuff needs to be built bigger and stronger and renewed more in dense urban areas. All I’m arguing for is let’s run the numbers. Don’t just assume city living is more ecological because it’s denser.
With that in mind, it's now possible to construct dense urban areas without relying on carbon-emitting concrete or steel going into the structure. Only wood, which is a carbon sink and can be sourced sustainably.
Given that this is fairly well-known - and that the impact of concrete on the environment well-studied - what is it that leads you to think that the numbers have not in fact been run?
It's of course possible to construct all sorts of weird versions of this comparison (tiny houses vs McMansions, ultra-modern mid-rises made from timber, etc. etc).
I suspect it's all moot given that transport is such a substantial component of energy use and these houses/apartments should last a long time.
All I’m saying is I don’t hear urbanists talking about the carbon footprint of construction. It’s like an article of faith that high density is ecological.
Eg just becuase it's short doesn't mean it's efficient, and tall doesn't mean inefficient.
What it means is we're all just arguing based on no data and instead preferences.
Hyper density isn't going to work in rural/farm/resource areas where people essentially need to spread out. Nor does super low density work where everyone essentially comes together to do things.
In the end I think you need to assume that all of the arrangements exist for a point on the multi-variate optimization curve, and just figure out commonalities that make them all more efficient overall, instead of re-aligning all living on a current single local optima.
Unfortunately politically it’s not so easy.
Nice Aptronym there
Are typos a known issue in searches? 1, I, or l, 0 and O
There are literally mountains of flyash laying around in Europe without anybody wanting to use them for concrete.
So, in other words bought and paid for by the taxpayer, and sold to the highest bidder on the commercial market.
So much for encouraging use of this stuff. It'll be priced right out of the market because it's "green".
Yes. And why this has become common practice might surprise you.
Universities used to try to open technologies up to anyone who might want to use them. Cool new thing, come use it, free to all humanity! Problem was, for the most part nobody wanted the free thing. University outputs typically require some non-trivial amount of investment and work to actually be commercializable, and few companies want to invest when they can't know they'll get a commercial advantage over the competition out of it.
Selling it on the commercial market, on the other hand, accomplishes two things. First, it puts some money back into the university, which might allow for more research for the taxpayer dollars (cool, right?). Second, it offers improved chances that the patents might actually turn into real stuff now that the owners of it have both a commercial interest and temporary exclusivity.
Some formulas on concentrator efficiency:
It looks like the highest temperature achievable for a trough-shaped solar collector is about 400 C, whereas for a parabola, it's closer to the temperature of the sun (at least 2000 C). Note that the maximum possible temperature achievable for any concentrator is the temperature of the source, by the laws of thermodynamics:
I don't have time at the moment, but maybe someone could derive the maximum temperature for a parabolic trough? I feel like it might be approximately the square root of a parabolic dish, but I don't know for certain.
I could put together buying ferrock in large quanties (over $1 million) because of the many bike paths and greenbelts that still need to be poured along the river, canals and train tracks in my city. But using concrete or asphalt is perhaps too environmentally unfriendly, and I haven't found a good alternative (say pavers) because we still want people to be able to skate and have a comfortable bike ride. We also have football field-sized piles of glass bottles waiting to be recycled that would be another free input along with solar heat.
Also if it wasn’t available 20 years ago there’s your reason.
I'm having trouble finding infrared conductivities:
So looks like aluminum nitride might be best (first made in 1877 so we have the technology!) with a melting point of 2200 C:
Portland cement (the basic ingredient of concrete) is made at 1450 C:
And looks like any aluminum from the crucible wouldn't contaminate the concrete. Not sure about the nitrogen, but since the air is nitrogen/oxygen, it should be ok:
But I think it's important to flip the problem on its head. Since solar thermal energy is essentially free after the solar furnace is manufactured, then we might as well scale it up to provide 2-10x more heat than we need, and then choose a ceramic with the material properties we want, even if its thermal conductivity isn't as efficient as we'd like.
Keep in mind that any heat we get from this will be roughly 4 times cheaper than from photovoltaics (running at 25% efficiency) since we avoid the light->electricity->heat conversions.
If you don’t do this then all the air in the room is also heated up to ludicrous temperatures, and that tends to be bad for any other equipment or people nearby.
As for iron dust, I have to agree. The only way I could see iron dust being practical is if this tech was able to repurpose industrial waste (rusted up sheet metal, old rebar, etc).
> It’s actually created from waste steel dust which is normally discarded from industrial processes and silica from ground up glass. The iron within the steel dust reacts with C02 and rusts to form iron carbonate. It’s this that is fused into the matrix of Ferrock and, like concrete, after it’s dried, it cannot be melted back into a liquid form but retains its hard, rock-like qualities.
> ... But there’s skepticism from the cement industry that while Ferrock could be great for niche projects, it isn’t practical for large-scale industrial use, like highways for example. If steel dust suddenly goes from being a “waste” material to a highly-prized building resource, it’s price will increase exponentially and the costs of producing Ferrock may limit its application.
"Large Saharan Collider – not what you think it is!"
That's why the Middle-Age alchemists couldn't make one.
Now we can.
To manufacture rock dust you:
1. Quarry rock.
2. Pulverize it.
1. Quarry ore.
2. Pulverize it.
3. Smelt it (which requires coke, a basket of worms in itself.)
4. Cast it.
5. Grind it.
5 times harder.. superlative concrete?