Air Travel Emissions Vastly Outpace Predictions • Hacker News Board

Re: Air Travel Emissions Vastly Outpace Predictions

#231

Post by mehrdadn » Fri, Sep 20, 2019, 9:10 PM UTC

sokoloff wrote: post #224

mehrdadn wrote: post #211

Earlier quoted context omitted.

Well, to be blunt, so what? That sucks for sales stuff, it's not like I said conferences are the only things that need to change. Maybe the practices there need to change there just like for conferences and other stuff. Nobody said it's easy or nice or effective or whatever for humans to do long distance. Just that you need to start sacrificing somewhere and I sure as heck find it more reasonable and humane to start…

"So what?" Incentives. If subgroup A doesn't travel for sales, subgroup B who travels will likely outcompete them by more than the cost of the travel, or subgroup C who is large enough to have many local offices will outcompete A, making it harder for new entrants to a market to compete and concentrating business activities in select cities (which is great if you're rich enough to live in those prosperous cities). I'…

Whatever you do, either some subgroup will find a way to take advantage of it, or you'll find a way to mess with taxes and incentives and prices enough to mostly compensate for the side effects. That's not a counterargument for a solution, it's already a given in the problem statement. If you find some magical way to avoid any and all collateral economic damage, I'm all for it, but I don't see why people should just wait for others to come up with miracles that may never come just because some businesses will inevitably win and others will inevitably lose.

Re: Air Travel Emissions Vastly Outpace Predictions

#232

Post by TeMPOraL » Fri, Sep 20, 2019, 9:11 PM UTC

sokoloff wrote: post #202

TeMPOraL wrote: post #124

Earlier quoted context omitted.

Re your first question, quick googling suggests some 37 billion tons of CO₂ per year. So sure, that's a lot. But then again, not that lot. Instead of asking questions, why don't you tell us why we couldn't possibly sequester that much carbon annually? How big is the divide between what we could do and what needs to be done? (I must say the idea of sequestering carbon seems emotionally appealing to me because it turns…

It seems to me like we need to do both: tax carbon (ideally globally, but even if half the developed countries do it, it's huge) AND use that tax money to work on research and deployment of carbon sequestration or carbon to fuel conversion.

That's my current belief too.

Re: Air Travel Emissions Vastly Outpace Predictions

#233

Post by Robotbeat » Fri, Sep 20, 2019, 9:11 PM UTC

I'm convinced we need zero emissions aircraft. Efficiency improvements alone are going to suffer from the Jevons Paradox. In fact, that "paradox" could help explain why air travel emissions have increased so much even as aircraft have gotten much more efficient. https://en.wikipedia.org/wiki/Jevons_paradox

So to avoid the Jevons Paradox, we need actually zero emissions aircraft. Battery-electric or possibly hydrogen are the main contenders, here.

Battery-electric in the near term is limited to about 1000km, maybe 2000km range. That's technically enough to do transatlantic crossings if you stop by Greenland and Iceland or possibly the Azores. And you could do transpacific by following the Aleutians. Pretty much the hardest place to visit is actually Hawaii. But for domestic flights, battery-electric is actually a superior option to high speed rail in the US. Typical HSR routes in the US are only about 300 miles or so, well within range of existing electric battery tech that could be adapted to airplanes, and even a fully subsonic, Mach 0.5 propeller-drive electric airplane would be much faster than even the fastest practical HSR. And operating at high altitude (with far lower air density) would mean that the electric aircraft would be more efficient than a hypothetical Mach 0.5 high speed train. But all of this will require probably non-traditional aircraft makers. The duopoly is culturally unprepared for the kind of radical engineering necessary to make a 1000km battery electric aircraft feasible (almost sailplane-like efficiency, combined with very high battery mass fraction, combined with extremely efficient battery packaging, state of the art structural mass, and transition to higher performance chemistry where possible).

Liquid hydrogen is also a possibility for electric air travel. Compressed room temperature hydrogen is hardly more energy-dense than battery-electric, though, so you're going to have to go at least cryogenic, if not liquid, for hydrogen storage. Liquid hydrogen wouldn't be too bad in this application since the time of storage wouldn't be too long, and the scale would be large enough (if used in a widebody aircraft) that boil-off may not be too much of a problem (besides, you need a constant feed of hydrogen anyway). But a big problem is the fact that anthropogenic high altitude water vapor is maybe even worse (by a factor of 2) for climate change than CO2, so you'd probably want to condense the output. That means using fuel cells and then storing the condensed water on board and doing occasional low altitude dumps (it may even be feasible to store the water for the entire trip, dumping only right before you land) or perhaps freezing the condensate into pellets (small enough to not pose a lethal hazard but large enough to not evaporate on the way down) and then dropping them along the way. So long-haul air is a major challenge.

Re: Air Travel Emissions Vastly Outpace Predictions

#234

Post by vonmoltke » Fri, Sep 20, 2019, 9:11 PM UTC

dredmorbius wrote: post #181

taylortrusty wrote: post #33

Earlier quoted context omitted.

You need to divide that 3.4 tons of carbon by the ~270 people on each flight

Aircraft use a lot of fuel. Roughly half the takeoff weight of an airliner is fuel. The fuel burned on a continental-distance (3000+ km / 2000+ mile) flight is roughly equal to the passenger's weight. CO2 emissions by mass exceed the mass of the fuel by a factor of three , as you're adding the mass of the oxygen that's added, far more than the hydrogen that's split off. https://www.engineeringtoolbox.com/co2-emission…

> At Shanghai-NYC distances, that's 34,300 kg of fuel

That's sounds very low for fuel burn at that distance for a 747. The 747-8 carries over 191,000kg of fuel, yet has a maximum range of only 14,320km.

As an aside, I wonder if using "carbon" as shorthand for "carbon dioxide" does more harm than good.

Re: Air Travel Emissions Vastly Outpace Predictions

#235

Post by Robotbeat » Fri, Sep 20, 2019, 9:12 PM UTC

alex_young wrote: post #120

j-pb wrote: post #101

If I take the train, which is the most green transport (CO2 neutral) from one edge of europe to the other (e.g. Berlin to Sicily), the amount I pay is 500 euros and it takes me 35 hours. If I fly the same distance it takes me 3 hours, and I pay 100 euros. Heres the kicker, it costs me 100 euro to buy CO2 compensation and make the flight CO2 neutral, and whenever me and my spouse fly we always pay twice that so that w…

That sounds great, but how do you manage to offset 2 flights? I don't really understand how money can undo putting a bunch of carbon in the atmosphere.

You're paying for pulling the carbon back out. The cheapest way to do this is to pay someone to plant trees for you.

Re: Air Travel Emissions Vastly Outpace Predictions

#236

Post by jalgos_eminator » Fri, Sep 20, 2019, 9:12 PM UTC

js8 wrote: post #219

blunte wrote: post #136

If you need to travel long distances, there's little substitute for an airplane. If air travel accounts for less emissions than passenger cars, and if the top 15 polluting large container ships produce as much (noxious oxides of nitrogen and sulphur) pollution as all cars, then we need to fix shipping first. And if you look at a lot of the crap that is being shipped, it's stuff we just don't need. A lot of things are…

Actually, there are substitutes. People who need to travel (and most of them don't) can just use trains or ships, and make the overall stay longer (decreasing overall number of trips). It was already possible more than 100 years ago, and it would be much less of a problem in today's digital economy.

There's only so much time each day, and a plane gets you to your destination so much faster. Trains? Maybe for shorter trips like NYC to Philadelphia or DC, but NYC to Seattle? A train going 150mph would take 19 hours for that trip not counting stops. It would probably be more than 30 hours with stops, and significantly longer if the train can't average 150 mph. The flight is 6 hours gate to gate. You can't beat the speed of modern air travel, its just so much better than any other alternative.

And no, most people can't just work from literally anywhere on a ship or train. That probably isn't even workable for a remote programmer let alone a marketing manager, welder, electrician, office assistant, salesperson, etc.

Re: Air Travel Emissions Vastly Outpace Predictions

#237

Post by ekianjo » Fri, Sep 20, 2019, 9:14 PM UTC

umvi wrote: post #58

jcims wrote: post #40

Earlier quoted context omitted.

What's the basic energy equation of sucking CO2 out of the atmosphere using state of the art today? In say megawatt hours per gigaton?

> What's the basic energy equation of sucking CO2 out of the atmosphere using state of the art today? Current state-of-the-art has the following equation[1]: 6CO2 + 6H20 + (photons) → C6H12O6 + 6O2 (sorry, I couldn't help myself, the setup was too good) But seriously, I doubt we can beat plants in terms of carbon sequestration efficiency. [1] https://sciencing.com/photosynthesis-equation-6962557.html

Plants consume about as much CO2 as they create. Its hardly sequestration.

Re: Air Travel Emissions Vastly Outpace Predictions

#238

Post by vonmoltke » Fri, Sep 20, 2019, 9:14 PM UTC

js8 wrote: post #223

TulliusCicero wrote: post #191

Earlier quoted context omitted.

People traveling, the tourism that is so often bemoaned, is a huge part of the connections between countries, a huge part of diversity and understanding. A world with greatly reduced air travel is a more insular and less understanding world.

> A world with greatly reduced air travel is a more insular and less understanding world. I don't think there is an evidence for that. It is more likely that immigration increases cultural understanding rather than travel. In any case, emissions of travel can be greatly reduced by using other modes of transport and by making the stay in the target country longer. Such a cultural shift could actually even improve the…

> It is more likely that immigration increases cultural understanding rather than travel.

What will the affect on immigration be if going back to the "old country" becomes significantly more difficult?

Re: Air Travel Emissions Vastly Outpace Predictions

#239

Post by TulliusCicero » Fri, Sep 20, 2019, 9:16 PM UTC

js8 wrote: post #223

TulliusCicero wrote: post #191

Earlier quoted context omitted.

People traveling, the tourism that is so often bemoaned, is a huge part of the connections between countries, a huge part of diversity and understanding. A world with greatly reduced air travel is a more insular and less understanding world.

> A world with greatly reduced air travel is a more insular and less understanding world. I don't think there is an evidence for that. It is more likely that immigration increases cultural understanding rather than travel. In any case, emissions of travel can be greatly reduced by using other modes of transport and by making the stay in the target country longer. Such a cultural shift could actually even improve the…

> I don't think there is an evidence for that. It is more likely that immigration increases cultural understanding rather than travel.

Disagree that travel doesn't matter, but even then, do you really think it being much harder to visit their home countries again will have no impact on immigration patterns?

> In any case, emissions of travel can be greatly reduced by using other modes of transport

Would love to hear how you propose to let Chinese and Indian immigrants in the states visit home sans airplanes

> by making the stay in the target country longer.

People would already take longer vacations if they could, dude. Making it harder and slower to get there isn't gonna help anything.

Re: Air Travel Emissions Vastly Outpace Predictions

#240

Post by finchisko » Fri, Sep 20, 2019, 9:17 PM UTC

>If you need to travel long distances, there's little substitute for an airplane.

the question if the distance you travel doesn't have substitute. like many business people travel just to meet, which has zero carbon alternative - video call.