Cement recycling method could help solve one of the big climate challenges

the normal kind of arc furnaces are shut down many times a day; it's a batch process, not a continuous one

You may be thinking of aluminum plants which can’t be shut down and restarted without significant damage, but they are indeed still throttled up and down. In that case it’s electrochemistry at high temperatures to strip the oxygen off of aluminum. If it gets cold the apparatus gets damaged, but it can be throttled down a significant percentage.

Arc furnaces tend to be first in line to voluntarily shutdown to deal with grid instability, or projected power shortages. Network operators will basically pay them equivalent amount of money as they would to buy electricity, if the furnace operator is happy to shutdown at a moment’s notice.

After, to a power grid, removing large loads are functionally equivalent to adding additional generation. So if you’re operating an arc furnace, and can shutdown quickly (which arc furnaces can), then grid operators will pay you for privilege of being able to shut you down at moments notice, and then pay even more for the electricity you’re not consuming, if the grid is forced to call upon that additional “capacity” due other issues on grid.

I’m not sure if arc furnaces today vary their usage in direct response to variable electricity prices through the day, rather than only acting as emergency ballast to be jettisoned in an emergency. But I would be very surprised if they didn’t, they’re a large enough load that they’ll have coordinate the usage with their local grid, and large enough that shifting the usage pattern to avoid high cost peaks would save them a very material amount of money.

Did you miss the stat directly underneath that?

> Heating and other energy-intensive water uses in homes and businesses make up almost 90% of water-related energy use, while treatment, pumping, and conveyance of water and wastewater account for the rest.

That's 2% for everything which isn't heating water. Pumping is some smaller fraction of that.

There's been other responses here pointing out that municipal water delivery pumping probably isn't a large electricity consumer, but it's also worth noting that even if it was you can't voluntarily shutdown water-delivery in large distribution systems - you have to maintain pressure and flow to prevent back contamination of the system from leaks. It's why you get boil-water advisories when there's a general outage - because dirt and bacteria can get back into the pipes and it takes time to be sure they've been flushed out of the system.

it's pretty moderate amounts of voltage actually, only about 300-900 volts, just a little higher than i plug my phone charger into. it's just massive amounts of current, resulting in massive amounts of heat, which sets fire to the impurities and/or boils them off. you need low voltage because the arcs are pretty low resistance, so getting the necessary power requires tens of thousands of amps, about the same as a lightning strike. an hour-long lightning strike

(the power of a lightning strike is much higher than that of a steelmaking arc furnace because it has much higher voltage, possible because the conductive path through the plasma is kilometers long instead of centimeters long)

youtube has automatically translated subtitles which worked pretty well here. the relevant yt-dlp flags are i think --write-sub --write-auto-sub --sub-lang en,es (season to taste) and then the j key in mpv cycles through the languages you chose. this is also possible from youtube's web ui but enormously more awkward

so, because this is steel recycling rather than smelting, almost exactly none of the energy used in the process ends up in the final product; 99% or more of it is lost as heat during the manufacturing process. one of the things mentioned in the video is that this furnace uses more electrical power than the entire neighboring town of witten (population 0.1 million), which means that you could heat all the houses. but you'd still need the big basins, because all the houses might not be enough to cool the furnace; certainly in the summer they wouldn't want to

creating electricity is unfortunately somewhat less practical due to the low temperatures of the water, although there are some interesting experiments with deriving power from low-temperature geothermal resources using n-pentane-blown turbines, and you might be able to use that work. getting the furnace's water jacket hot enough to boil water would create the risk of a steam explosion as well as increase plumbing corrosion problems

i mean, it would create a larger risk than the one that already exists due to having a water jacket in a place where a furnace damage could mix water with molten steel—as it turns out, cooling water is already the major cause of fatal accidents in electric arc furnaces, causing several fatal electric arc furnace explosion accidents every year: https://www.aist.org/AIST/aist/AIST/Publications/safety%20fi... and this is stimulating a movement away from pressurized water jackets for electric arc furnaces (at least, if we can believe this marketing white paper from a company that sells non-pressurized electric arc furnace water-cooling systems)

you could conceivably use a different, higher-temperature coolant than water, such as molten salts or sodium, as is done in nuclear reactors, so you could have an unpressurized coolant loop (maybe even using a coolant that wouldn't react violently with molten steel the way water does) but these do have disadvantages; water has a really astonishing ability to transfer heat by nucleate boiling

but then you run into the cost issue: the reason coal plants are not able to produce electricity at a price that is competitive with solar farms is, as i understand it, that the steam-turbine and electromechanical generator part of the plant still cost more than solar power, even in very polar countries like germany, whose utility-scale photovoltaic capacity factor was 10% last i checked. it's not because of the cost of coal; even if coal was as free sunlight, they'd be uncompetitive. and the same cost problem would make it uneconomic to generate electricity from the waste heat from electric arc furnaces, even if you could get the heat out at a more useful temperature. every million dollars you hypothetically spend on recycling eaf waste heat into electricity would have produced more electricity if you had spent it on solar farms and wind turbines instead

district heating is a good idea tho. i wonder if witten is already doing it?

I dont think that suggests there is a high demand for used concrete. It does however highlight the fact that there may be insurmountable transportation and handling costs for recycled concrete.

It is hard to imagine it being cost effective to transport it to recycling centers.

old concrete is not in high demand. unfortunately, when i try to follow your link it just says 'fuck you, wetback scum', like every home depot page, so i'm not sure what your evidence is. are they offering you money for your old concrete? how much are they paying?

something like 15% of the material that gets carted to landfills is old concrete

generally speaking, old concrete is used in new concrete as (very) coarse aggregate. alternative coarse aggregate is mostly angular crushed stone, like the track ballast you see around railroad tracks. this is made by dynamiting deposits of limestone, granite, or basalt and feeding it through a rock crusher. while this sounds violent and energy-intensive, it's nothing compared to running a cement clinker kiln. most of the cost of coarse aggregate is from the cost of shipping it, not the cost of the energy needed to crush it; as wp says

> Large stone quarry and sand and gravel operations exist near virtually all population centers due to the high cost of transportation relative to the low value of the product. Trucking aggregate more than 40 kilometers is typically uneconomical

Putting old concrete into roads loses almost all of its value and is a pretty atrocious form of downcycling; notice that the linked article is literally about “disposing” of concrete, not re-using it meaningfully. Most of concrete’s primary use case is as a structural material in buildings/infrastructure - beams, columns, slabs, etc, and we unfortunately have very little by way of re-using concrete structurally, partly due to demolition processes, documentation, rebar etc etc. While pre-cast concrete is potentially more up-cyclable, again, it’s not really designed for disassembly, re-assessment, etc, and there are very few actual use-cases/projects that have done anything of the sort, though some very cool research is being done on this at places like MIT and EPFL, including novel pre-cast concrete systems specifically designed for dis-assembly and re-use.

Part of what makes the article and methodology linked here interesting is that it a) uses waste heat which b) is already theoretically able to come from renewable sources and c) can be used to to support manufacturing of structural components further upstream in the lifecycle of cement/concrete.

Steelmaking takes place around 1650C. Getting up to molten steel temperatures is hard.

Yes, you could potentially use waste heat from a reactor to preheat the tundish, and maybe the scrap and ladle. Nucor preheats using natural gas to save on electricity. No need to bring everything up from room temperature on electric power. A nuclear reactor immediately adjacent to a steel caster is probably not a great idea.

Wind and solar supplied 12% of global electricity in 2022 up from 10% in 2021 and things are still accelerating. You can’t keep this kind of growth rate up for long before things change. https://www.cnbc.com/2023/04/12/wind-and-solar-generated-a-r...

Your capacity factor numbers are also off ex: 29.7% capacity factor averaged over 3 years https://en.wikipedia.org/wiki/Mount_Signal_Solar.

Thermal is also much lower than your suggesting. China the world’s #1 coal consumer has capacity factors under 50% because they are using them for load following. France’s nuclear averaged ~70% for years for similar reasons. It’s only where the there’s excess natural gas and minimal solar/wind that thermal can keep high capacity factors but that’s becoming rare.

This logic does apply to fossil fuels because fossil fuel plants cannot compete on cost with renewables when they’re running at full capacity. In terms of actual production, many fossil fuel plants are running at lower than their potential production.

Probably because the base is changing fast enough that it’s hard to compare percentages of the total population over time. Geometric growth is kind of hard to follow.

My numbers might be slightly out of date. It makes sense for energy generation to have grown recently.

For oil and gas energy usage, you should take into account that usable energy and energy consumption are two things. When electrifying, you typically end up needing less energy overall. The notion of replacing oil twh with solar twh is simply wrong. This is something the IEA gets wrong in most of its reports. Which is one reason why their estimates and predictions keep having to be corrected by them every few years.

A good example is ICE cars vs. EVs. A gallon of gas represents about 33.7 kwh of energy. A Tesla can do over 4 miles per kwh. Most ICE cars get nowhere near 120 miles per gallon. Anything over 1 mile per kwh of gas is actually pretty good. Especially for bigger cars. So, an ICE car wastes about 70-80% or more of its energy (heat, noise, vibrations, friction, etc.). You see the same pattern in other sectors where electrifying usually also means improved efficiencies. Most Teslas only have 2-3 gallons worth of kwh in the car. An ICE car with a tank that small would have a terrible range.

So, a doubling or tripling of electricity generation might actually be good enough to replace most fossil fuel usage.

Northern Africa has a lot of cheap land and a lot of sun. Wind, too. Steel can be then transported (it is already shipped across large distances). You would have to solve maintenance, but that should be doable.

The main obstacle for investment is political stability and alignment.

There's another catch to your calculation: arc furnaces use scrap steel, which is only enough to supply 30% of the world's demand at this time. That's why 30% of steel is from electrical power. AFAIK most of the furnaces are already built in places with plentiful renewable power to take advantage of negative power prices. There are furnaces in Europe that operate only when the power is free.

Most of the world's steel is produced from ore, which not only requires three times the energy of recycling scrap but also vast quantities of carbon from fossil fuels to incorporate into the alloy. I believe there's a relatively new electrolytic process for the ore but at far smaller scale and it requires even more power.

Of course, but in cases where there's a defined endpoint we also know that the decay from the exponential looking phase is going to happen well before we get there.

i.e. the solar industry won't start installing solar panels at an ever higher rate if the amount of solar penetration is almost 100%. In fact the relative value of installing panels will decline as we get nearer to it. Arguably that's already happened - i.e. power prices going negative scrapes a lot of the shine off private industry funding them.

Versus say, a natural process where while this might happen, the bounds aren't limited by humans making economic decisions for themselves (which of course, when you think about it also implies dangers in extrapolating effects of natural processes like climate change - the rate of some downstream parameter going up and looking linear and shallow could just be a very large system in the middle of moving into an exponential phase which extends well beyond our ability to manage it).

Counter-intuitively, wooden buildings when properly designed are not especially dangerous from a fire safety point of view.

I do have blog posts about all of those things, but that's more my "shower thoughts" pile:

• https://benwheatley.github.io/blog/2022/05/14-17.06.59.html

• https://benwheatley.github.io/blog/2021/07/31-13.37.34.html

• https://benwheatley.github.io/blog/2017/04/20-14.32.32.html

• https://benwheatley.github.io/blog/2024/04/24-10.42.51.html

I like the implication that FTL is closer on the horizon than electoral reforms

Within their corp? Or throughout their whole supply chain + peripherals?

Is their cleaning contractor also net zero?

With promises like these the devil is in the details. You could have one true in spirit net zero company on the one side and another net zero shell company that has 1000 crazy polluting sub-contractors.

Given the fact that many big corps can't even prevent child and slave labor within their supply chain, I have to say I believe it when I see it.

Thats just a “commitment” - not in any sense an achievement. That its only half, at this late hour, rudely betrays how badly the market is failing to solve this problem.

It's not happening at any pace. CO2 is going up like it always was. No dent. We need to destroy society, not develop more technology.

> Why is it a limited resource world?

That is probably a more profound question than you might think. But one answer is, because we are in the saturation area of the logistical curve. Just like the feedback of a guitar amp infinitly amplifying itself, there is a point where it won't get any louder as you run into the physical limits of its electrical components, changing the sound of everything fundamentally.

We are limited because our earth is a globe with a atmosphere so thin, if you scaled the earth down to the size of an apple its peel would be way thicker than the Earth's. It is limited for the same reason my living room is limited: It has a certain geometric extent and that's it.

Let's say I put stuff into this room. If my goal was to put 5% more stuff into that room each week you probably would angle your head and ask me if I was crazy. Rightfully so.

Now my point was precisely this: growth sucks as an organizing principle in a world of limited resources. It would be better to figure out how to make use of the resources in a better way. Ans we even know how to do this on a smaller level.

But somehow we ended up with a ruling class that well.. doesn't profit from extracting value from putting more stuff into the room, so we do just that.

Because the USA can export their problems to the rest of the world.