Dave & Rebecca - this interview was amazing! Thanks so much. Rebecca is a fount of knowledge and a brilliant speaker/teacher. Such lucid, systematic thinking.

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Hey Awesome. Rebecca is a former AAAS Science and Technology fellow like myself and we overlapped at DOE. Great guest!

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Thanks for a really useful overview. A few of us at 350 Seattle had a call with some national folks yesterday (nonspecialists in concrete, so they didn’t want to be quoted on all this), and they raised some issues with how Dell talked about concrete (specifically, the fact that she thinks this is where we should learn to love CCS). This is an abbreviation of my notes:

Concrete has 3 sources of CO2 emissions:

Power (40-45%): can be electrified

Process emissions: they say the fossil fuel industry is banking on concrete helping to sell CCS more broadly, but <6/10% of all US emissions come from concrete, across 96 facilities. So there aren't large volumes of emissions in one spot. Cement factories generally have 3 factors that drive where they’re built: proximity to limestone quarries (limestone is heavy), proximity to end use markets (concrete is heavy), and proximity to water (they need lots of water). None of that has anything to do with good locations for stored carbon, so CCS is not appropriate in that sense, except in Texas. In the PNW, if you look at geological survey reports on viable CCS storage areas, we have the fewest anywhere on the continent. Would have to move it through zillions of miles of pipeline….and, of course, most CO2 captured is just used to get more oil.

No one talks about the third source: transport. The US imports 10x as much cement as it exports. One of the best ways to reduce emissions is to produce it domestically using renewables. Also electrifying mixer vehicles, prime candidate, freightliner has electric semis that already have a million miles on the road, same platform as the mixers (semi class 8).

Re: clinker adjustment, they think this goes to solutions convenient to industry, and isn't very effective. It uses things like fly ash, steel slag….this takes toxic waste & uses it. The major downside is that putting these wastes in concrete leads to leaching of heavy metals. If you put combustion waste or slag in the cement, you’re reducing the amount of new material, but it’s not meaningfully positive.

Blue Planet tells story of captured CO2 used IN the cement, but they don’t say how much (very little), and the slag is the vast majority of avoided emissions.

But we can also use recycled cement in the mix (this involves only crushing emissions, not manufacturing emissions).

In EU, they already have electrified cement trucks. Built on a semi class 8 platform. We have those, but not the mixers. Freightliner's E-Cascadia, which has gone 1 million+ miles. Everyone is developing them now, including local Paccar.

In short, it seems like the best routes forward for greatly reducing emissions from concrete seem to be:

1. Stop wasting it, immediately (almost free!)

2. Don’t import cement (currently comes in from both BC and China)

3. Electrify the manufacture

4. Use more recycled concrete in the mix

5. Electrify the transport

Would you agree that that's basically right? The numbers are very complex, but my hunch at this point is that if we can do all this in the next 5 years (locally, I mean), concrete may be better than wood even just on the basis of CO2, let alone the other benefits of forests. (Those of us on the call had different reasons for being there, but mine is that we're starting up some forestry work, and I'm trying to get a good sense of what our possibilities for dense affordable urban housing, if we ALSO want to retain our legacy forests, which absorb more CO2 than any others in the world.) Of course it also matters what happens with steel...

Lastly, do you have any idea what policies might effectively mandate big reductions in wasted concrete, as described on the podcast? Has anyplace even tried to do this? How do we get around the fact that it’s so cheap compared to labor, that GC’s are happy to waste it if it saves a few minutes?


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This was a fascinating episode!! Thank you I needed all of it :)

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Fantastic interview—so nice to hear clearly delineated solutions in a thoughtful and organized manner! Both of you keep up the good work.

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I enjoyed this podcast episode a lot. I'd love to hear more from Rebecca on this podcast. And yes, I was one of the folks who made it all the way through to the end! 🙂

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Not only made it to the end, but wanted more! Very informative, especially the part about plastics.

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Finally got around to paying for a subscription. Thanks Dave for all you have been working on, I really value your writing and podcasts. This was an exceptional interview and I learned so much about a topic that I knew very little about previously. It's exciting to see that in almost every domain there is a feasible roadmap toward a clean future if we have the political will to make it happen (looking at you, Manchinema).

I found the discussion about the economic importance of steel mills and the political implications very interesting. Very grateful that there are methods for decarbonizing existing mills (via CCS or hydrogen-based shaft furnaces) as it seems like that would be a very difficult political battle if it were truly necessary to move mills geographically to areas of cheap electricity.

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Best in a while. Breaking down the sectors into discrete non-overlapping areas is tough to do but necessary for rational policy. So, that's good. I would like you to do a thought exercise. If you were empowered to lay our the most rational cost-effective and efficient pathway to emission-free energy, what would it be? The path must keep modernity largely intact and include policies that protect the people (not the financial interests of interested parties) who will be impacted in the transition. In other words, lay out the fastest, simplest, and cheapest way. Then go back and suggest high-level policies that will deal with the social impact. So often we are sidetracked on political and social and technical issues. Then we try to figure out the best outcomes for the vested interests, and the sphere of vested interests keeps expanding. We're not just dealing with fossil fuel interests, we have the utilities and their business models that actually incentivize more expensive energy. We have the tribes who supply workers at coal plants, we have hydrogen which is more a less of device to boost natural gas use, and so on. We shouldn't allow ourselves to be sidetracked. We need practical solutions, not market solutions.

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For a much more skeptical data based take on industrial decarbonizing see Alice Friedemann’s Life After Fossil Fuels. I hope Rebecca is correct in her optimism but Alice seems to have the upper hand at least from the perspective of this non technically sophisticated climate policy nerd.

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Thanks. We get notified, right?

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Amazing interview - well done David and thanks Rebecca.

Points I'd be interested in following up:

1. In aluminium production, it's pretty hard to utilize renewable electricity, because the power supply needs to be very stable - if the molten alumina gets too cold, it freezes and destroys the equipment. Is this also true if you electrolyze molten iron ore? That would essentially rule out direct electrification, I would think, and basically leave DRI with green hydrogen as the only pathway.

2. I've read that recycling has become much easier for cement, in recent years - what are the prospects here?

3. How many different plastics are actually needed to do the majority of things we need them to do? Could policymakers restrict plastics (at least, in common use, e.g. packaging) to a low enough number that recycling becomes easy, or even a profitable enterprise?

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