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> there are applications like long-haul jets and cement production where eliminating emissions isn't that easy. I disagree, there's an easy solution to elimina

> there are applications like long-haul jets and cement production where eliminating emissions isn't that easy. I disagree, there's an easy solution to eliminating those emissions: have zero long-haul jets and zero cement production. Before this gets (inevitably) downvoted, the more interesting question is why do we need either, what alternatives are there, how fundamentally we're willing to question our biases and expectations over what counts as a necessity. If saving our environment is an overriding priority, then the extent of the compromises we have to make can be made clearer.

HPsquared 5y ago
It's not actually easy to ban long-haul travel. It's technologically simple, which is probably the angle you are looking from, but politically very difficult.
- ashtonkem 5y ago
  We can drastically reduce our usage of jets though. There is no reason why people should be flying between SF and LA, or NYC and Boston. Those are well within comfortable range of high speed rail, which is electric. Once we’ve shifted all the excess air travel over to rail, that will leave a much smaller set of jet travel to offset.
  - spfzero 5y ago
    If you look at a map of all airline flights there are many thousands of short-range flights. Replacing them all with trains would be interesting. Just the right-of-way property transactions would be daunting. Look at California as a lesson in how this can't be easily done. The other thing is, people move around. Airlines can change flights easily to map to demographic changes; that's a major strength of air travel. Not as easy to rip up tracks and start over.
    - Robotbeat 5y ago
      It's much easier, IMHO, to switch over these short haul flights to electric aircraft than to High Speed Rail in the US. By the time even one major new HSR route will be finished, we'll have certified and be flying electric passenger aircraft with just as much speed and just as long of a route (500 miles) BUT with ability to go anywhere in the country by hopping.
      - GekkePrutser 5y ago
        I kinda doubt it will go that quickly. See how many problems Boeing had with their lithium batteries in the 787. And those were just auxiliary power. This will take a hundred times that many batteries with the scale bringing many engineering challenges. And then the totally different engines.. I think it'll take a long time to have a battery powered airliner built, in mass production and as reliable and safe as current airliners. There's a lot of stuff to be built from scratch without half a century of trial and error to learn from. I think biofuels might be a better option for aviation until the tech has time to catch up.
      - ashtonkem 5y ago
        I'd love for that to be true, but I am quite dubious. Flight technology tends to be very weight sensitive, and our battery densities are just nowhere close to the density that flight needs. Current batteries have an energy density of 90-190 Wh/kg, depending on the specific chemistry. Jet fuel on the other hand has an energy density around 12,000 Wh/kg. Obviously some amount of that will be made back up with the relative light weight and high efficiency of electric motors, but that is a very step energy difference to overcome. A quick bit of Googling says that turbofan engines are about 40% efficient, while triple phase electric motors are roughly 85% efficient. Given the 3,000 nautical mile range of a 737NG, some back of the envelope math says that an EV equivalent would have a range of about 100 miles at best[0]. Forget LAX -> SFO, this isn't even enough to get you from LA to Bakersfield. And even 100 is optimistic, given that the FAA requires that all planes have extra fuel for diversions, weather, holding, etc. At this point, I suspect it might be easier to refine kerosene out of capture CO2 using excess renewable energy than it would be to make an EV 737 replacement. 0 - I'm obviously not accounting for weight and aerodynamic differences, which are beyond my capability to estimate, but I doubt that would make a significant difference. I'm also assuming that we're using Li-Ion Cobalt batteries, which have the highest density. The more common Phosphate chemistry makes these numbers even more bleak.
deleted 5y ago
[deleted]
jjk166 5y ago
This would be a lot more insightful if we hadn't already spent decades and billions of dollars looking for greener alternatives only to find that they don't exist.
karaterobot 5y ago
Upvoted, because I think it's a legitimate question. I don't think you're actually saying let's stop all long-haul flights and cement production. You're saying that if we actually believed something was an existential risk to civilization, we'd put almost any option on the table for mitigating it, even if only to rule it out. I assume there is a list of sacred things we wouldn't even consider doing without, no matter the cost in human lives. But is jet travel and cheap construction on that list or not? Maybe, maybe not.
- Robotbeat 5y ago
  Concrete and jet travel are not existential. They're a few percent of the total. 3% for cement and 2% for aviation. Less than 1% for long haul aviation. If that was it the only thing left, we'd have no problem. That's at pre-industrial emissions level. https://ourworldindata.org/uploads/2020/09/Emissions-by-sector-%E2%80%93-pie-charts.png https://ourworldindata.org/uploads/2020/09/Emissions-by-sect... Long haul aviation makes immigration feasible without dangerous long ship trips, which are worse emissions than long haul aviation. So we should keep them around in some form, but we can improve the efficiency and even electrify them.
Robotbeat 5y ago
I would say it's pretty dang tough to not have cement. What do you use for a house foundation? Many apartments are made of cement and essentially every building uses a cement foundation. Luckily, cement is not a big part of the total emissions. Neither is long haul travel, particularly. Short haul flights are about half of all passenger-miles in air travel, can be made fully electric, and long-haul and medium haul flights can be split up into multiple legs for almost every route. EDIT:I will say there are ways to reduce CO2 emissions from cement. You can make clinker with electric heat just fine. But half the CO2 is from the clinker itself. Over time, cement will absorb the CO2 it emitted as it fully cures, but that can take a century. It’s possible to accelerate that process. It’s also possible to use alternatives, like sulfur cement.
- loufe 5y ago
  > Luckily, cement is not a big part of the total emissions. This is patently false. A quick search shows a number of 8% of global CO2 going to cement production and use emissions.
  - Robotbeat 5y ago
    “Patently false?” No, I see 3% in direct emissions from the cement itself: https://ourworldindata.org/uploads/2020/09/Emissions-by-sector-%E2%80%93-pie-charts.png https://ourworldindata.org/uploads/2020/09/Emissions-by-sect... (As far as indirect emissions like transport, the heat to make the clinker, etc, then yeah, I can believe that it gets to 8% total.)
- vbezhenar 5y ago
  > What do you use for a house foundation? Rocks. > Many apartments are made of cement Make them from wood.
- Emma_Goldman 5y ago
  >Neither is long haul travel, particularly. Aviation and shipping make up 5-6% of GHG emissions, not a trivial amount. Aviation is projected to expand several-fold by 2050 which, in the context of decarbonisation, means it will take up a progressively larger fraction of global emissions over time. It will be one of the last and greatest challenges - which is exactly why it will require offsets, carbon capture or otherwise. The aviation's offset market, CORSIA, is already one of the most developed in the world. Your optimism about electrifying aviation is not shared by the industry.
Dylan16807 5y ago
But why make it so binary? We can make biofuel at some price. We can capture CO2 at some price. Build that into the product and there's no reason to reduce to zero.

HPsquared 5y ago

It's not actually easy to ban long-haul travel. It's technologically simple, which is probably the angle you are looking from, but politically very difficult.

ashtonkem 5y ago
We can drastically reduce our usage of jets though. There is no reason why people should be flying between SF and LA, or NYC and Boston. Those are well within comfortable range of high speed rail, which is electric. Once we’ve shifted all the excess air travel over to rail, that will leave a much smaller set of jet travel to offset.
- spfzero 5y ago
  If you look at a map of all airline flights there are many thousands of short-range flights. Replacing them all with trains would be interesting. Just the right-of-way property transactions would be daunting. Look at California as a lesson in how this can't be easily done. The other thing is, people move around. Airlines can change flights easily to map to demographic changes; that's a major strength of air travel. Not as easy to rip up tracks and start over.
  - Robotbeat 5y ago
    It's much easier, IMHO, to switch over these short haul flights to electric aircraft than to High Speed Rail in the US. By the time even one major new HSR route will be finished, we'll have certified and be flying electric passenger aircraft with just as much speed and just as long of a route (500 miles) BUT with ability to go anywhere in the country by hopping.
    - GekkePrutser 5y ago
      I kinda doubt it will go that quickly. See how many problems Boeing had with their lithium batteries in the 787. And those were just auxiliary power. This will take a hundred times that many batteries with the scale bringing many engineering challenges. And then the totally different engines.. I think it'll take a long time to have a battery powered airliner built, in mass production and as reliable and safe as current airliners. There's a lot of stuff to be built from scratch without half a century of trial and error to learn from. I think biofuels might be a better option for aviation until the tech has time to catch up.
    - ashtonkem 5y ago
      I'd love for that to be true, but I am quite dubious. Flight technology tends to be very weight sensitive, and our battery densities are just nowhere close to the density that flight needs. Current batteries have an energy density of 90-190 Wh/kg, depending on the specific chemistry. Jet fuel on the other hand has an energy density around 12,000 Wh/kg. Obviously some amount of that will be made back up with the relative light weight and high efficiency of electric motors, but that is a very step energy difference to overcome. A quick bit of Googling says that turbofan engines are about 40% efficient, while triple phase electric motors are roughly 85% efficient. Given the 3,000 nautical mile range of a 737NG, some back of the envelope math says that an EV equivalent would have a range of about 100 miles at best[0]. Forget LAX -> SFO, this isn't even enough to get you from LA to Bakersfield. And even 100 is optimistic, given that the FAA requires that all planes have extra fuel for diversions, weather, holding, etc. At this point, I suspect it might be easier to refine kerosene out of capture CO2 using excess renewable energy than it would be to make an EV 737 replacement. 0 - I'm obviously not accounting for weight and aerodynamic differences, which are beyond my capability to estimate, but I doubt that would make a significant difference. I'm also assuming that we're using Li-Ion Cobalt batteries, which have the highest density. The more common Phosphate chemistry makes these numbers even more bleak.

deleted 5y ago

[deleted]

jjk166 5y ago

This would be a lot more insightful if we hadn't already spent decades and billions of dollars looking for greener alternatives only to find that they don't exist.

karaterobot 5y ago

Upvoted, because I think it's a legitimate question. I don't think you're actually saying let's stop all long-haul flights and cement production. You're saying that if we actually believed something was an existential risk to civilization, we'd put almost any option on the table for mitigating it, even if only to rule it out. I assume there is a list of sacred things we wouldn't even consider doing without, no matter the cost in human lives. But is jet travel and cheap construction on that list or not? Maybe, maybe not.

Robotbeat 5y ago
Concrete and jet travel are not existential. They're a few percent of the total. 3% for cement and 2% for aviation. Less than 1% for long haul aviation. If that was it the only thing left, we'd have no problem. That's at pre-industrial emissions level. https://ourworldindata.org/uploads/2020/09/Emissions-by-sector-%E2%80%93-pie-charts.png https://ourworldindata.org/uploads/2020/09/Emissions-by-sect... Long haul aviation makes immigration feasible without dangerous long ship trips, which are worse emissions than long haul aviation. So we should keep them around in some form, but we can improve the efficiency and even electrify them.

Robotbeat 5y ago

I would say it's pretty dang tough to not have cement. What do you use for a house foundation? Many apartments are made of cement and essentially every building uses a cement foundation. Luckily, cement is not a big part of the total emissions. Neither is long haul travel, particularly. Short haul flights are about half of all passenger-miles in air travel, can be made fully electric, and long-haul and medium haul flights can be split up into multiple legs for almost every route. EDIT:I will say there are ways to reduce CO2 emissions from cement. You can make clinker with electric heat just fine. But half the CO2 is from the clinker itself. Over time, cement will absorb the CO2 it emitted as it fully cures, but that can take a century. It’s possible to accelerate that process. It’s also possible to use alternatives, like sulfur cement.

loufe 5y ago
> Luckily, cement is not a big part of the total emissions. This is patently false. A quick search shows a number of 8% of global CO2 going to cement production and use emissions.
- Robotbeat 5y ago
  “Patently false?” No, I see 3% in direct emissions from the cement itself: https://ourworldindata.org/uploads/2020/09/Emissions-by-sector-%E2%80%93-pie-charts.png https://ourworldindata.org/uploads/2020/09/Emissions-by-sect... (As far as indirect emissions like transport, the heat to make the clinker, etc, then yeah, I can believe that it gets to 8% total.)
vbezhenar 5y ago
> What do you use for a house foundation? Rocks. > Many apartments are made of cement Make them from wood.
Emma_Goldman 5y ago
>Neither is long haul travel, particularly. Aviation and shipping make up 5-6% of GHG emissions, not a trivial amount. Aviation is projected to expand several-fold by 2050 which, in the context of decarbonisation, means it will take up a progressively larger fraction of global emissions over time. It will be one of the last and greatest challenges - which is exactly why it will require offsets, carbon capture or otherwise. The aviation's offset market, CORSIA, is already one of the most developed in the world. Your optimism about electrifying aviation is not shared by the industry.

Dylan16807 5y ago

But why make it so binary? We can make biofuel at some price. We can capture CO2 at some price. Build that into the product and there's no reason to reduce to zero.