[1] https://co2.myclimate.org/en/portfolios?calculation_id=75775...
[2] e.g. https://ieep.eu/publications/carbon-inequality-in-2030-per-c...
To sequester the ~800 Mt of CO2 emitted by aviation annually, you'd need to sequester about 400 billion kilograms of wood. So a finite but absurd amount.
It's just nowhere near in reality, and we're not going to make a large dent via sequestration, the "finite" airports is functionally infinite for our purposes. We have to start making carbon neutral fuel.
That said, manufacturing concrete is incredibly carbon intensive, so avoiding making the amount we would've needed for this building is a pretty good win.
Burying wood that would have taken decades to decay is not equal to instantly releasing the equivalent amount of carbon. I'm not sure it's physically possible to remove CO2 from the atmosphere at the same rate a plane emits it, which would be the only way to genuinely "offset" the emissions.
It looks like Skanska is GC for the Project, and cites it as a 9 acre (!) lumber roofing system[SK], and that it uses 3.5M board foot of Douglas Fir Project Lumber[PL].
Douglas Fir is 3.2 pounds per board foot, or 1.45kg [DFM]. So 1.45 * 3.5M = 5Mkg of lumber for PDX airport.
DF has an Embodied CO2 of 1.6kgCO2/kgLumber [DFC]. A little hard to believe? But maybe that's bc a lot of the mass of a tree is left in the ground. Worth following up.
1.6kgCO2/kgLumber * 5MkgLumber = 8MkgCO2 = 8KtCO2 embodiment/sequestration from the PDX roof project. (tho there's a lot more to the project that probably goes in the other direction)
Global CO2 emissions from commercial flights is ~60MtCO2/month [CF], so we need roughly 12,000 airports per month, 144,000/yr, to offset flight CO2 emissions.
There's 9000 commercial airline airports [NA] (tho obv many smaller than PDX, but they would also represent less CO2 from their flights), so 144,000/9000 is a 16x annual airport rebuild rate we'd need to offset CO2 emissions from the flights they service.
So yeah, this is absurd on the face of it.
But, how much of the mass of an airport is the roof? If it's like 1/100th the total mass, and you start building airports with all wood (foundation, runways, etc) you'd get to 16% annual rebuild rate to offset flight emissions. Still too high to be plausible. But another 10x somehow and you get to ~1% range of annual airport rebuild rate to offset emissions.
Then you'd have something.
[SK] https://www.usa.skanska.com/what-we-deliver/projects/278172/...
[PL] https://www.forbes.com/sites/johnoseid/2024/08/19/portlands-...
[DFM] https://www.globalwood.org/tech/tech_wood_weights.htm
[DFC] https://www.douglasfir.co.nz/net/environment/carbon-footprin...
[CF] https://www.statista.com/statistics/1500409/global-aviation-...
[NA] https://sentinel-aviation.com/blog/over-40000-airports-in-th...
But concrete is not so CO2 intensive. Lumber has a +1.6 sequestration factor of CO2 emitted vs built mass, compared with concrete at -0.8.
So we'd need runways made mostly of wood, or combined with a Woodcrete that was net sequestering, and then maybe there's a way to make even our most CO2 intensive industries net neutral so long as we rebuild continuously.
Also, since construction is about 40% of global CO2 emissions, if it could become a net sequestration as a whole, maybe it could flip the sign to -40% and offset most of the rest of our industrial emissions.
This also got me interested in what's a good number for rebuild rate.
Found a study that concludes the "Apparent ecosystem carbon turnover time [T]" is 43±7 years.
So maybe we should be rebuilding our built environment at 2.3%, or probably higher since species have evolved to be more energy intensive, humans especially.
[T] https://essd.copernicus.org/articles/12/2517/2020/essd-12-25...
I mean, this is obviously why this is just a fun math exercise and not much else. Building an airport, even if you build part of it out of wood, is not net carbon-negative.
Most uncertainty is how much mass the ceiling is compared to rest of airport. Maybe it's more like 1/10th. Hmm
That's 3.364×10^6 m3, 1 m3 of concrete weighs 2.4 tonnes (I'm sure it varies), so roughly 8 million tonnes of concrete.
https://www.concreteconstruction.net/_view-object?id=0000015...
I'm not convinced the wood used in the Portland airport project is net negative in itself, once you factor in the emissions of harvesting, processing and transporting it. I.o.w. leaving the ugly old roof in place would probably have been better, in terms of CO2eq emitted.
The Embodied Carbon figure they use is 1.64kgCO2/kg timber as a rule of thumb [ISE-EC], and agrees with what I posted above
For processing that yields built lumber, they account in stages, with % CO2 emissions added:
A1) Raw Material Extraction, 20-25% A2) Transport to Facility, 8-10% A3) Manufacture, 5-10% A4) Transport to Site, 50-55% A5) Construction, 10-15%
A1 to A3 reduce sequestration by 0.28, for a net of 1.36. They then say A4&5 account for 1.5x more emissions than A1-3, so .42kg total factor, for a net sequestration of 1.22kgCO2/kgBuiltLumber. They separate these as the transport is the largest variable between projects.
These figures are from Austria to UK. From the reporting, the PDX project is using mostly local wood.
So I think they're getting a net sequestration for the roof project.
It's really interesting that building with wood has this major sequestration factor. It'd be really something if we could build our way out of the environmental crisis just by switching to wood! :)
[ISE] https://en.wikipedia.org/wiki/Institution_of_Structural_Engi...
[ISE-EC] https://www.istructe.org/IStructE/media/Public/Resources/ARU..., p17: "The amount of carbon sequestered can be assumed as -1.64kgCOe per kg of timber when product-specific data is not available". I take the e to be emission, so a negative is a sequestration.
https://chancerylaneproject.org/glossary/carbon-dioxide-equi...
https://en.wikipedia.org/wiki/List_of_the_busiest_airports_i...
Train travel is expensive and sparse and slow, biking most places is uncomfortable and unsafe due to crappy infrastructure.
It is dumb to give up modern comforts when we know how to make them green by making electricity renewable and electrifying everything. Changing habits like reducing driving and increasing transit would help. Some things will be hard, like airplanes and concrete.
I agree somewhat that there is lots of distractions. There is a lot of talk about plastic and recycling that really has little to do with climate change.
I accept there is not a story for air travel, yet.
That's kinda the point though. You don't want it degrading in situ. That's why we treat wood.
In a situation indoors like here it will suffer less but still.. I used to live in a wooden house and the maintenance was a PITA. Having to repaint every 5 years or so. And that was wood that was treated already.
That whole Northeast is just screaming for it with easily managable distances. Boston, NYC, Philly, Baltimore, DC.. All easily high-speed-trainable. Boston to Portland too, for that matter.
Instead of spending 1 hour queueing at the airport, spend one hour on the train and you're there.
Vs. high-speed trains went out of fashion (in America) well before most people's memories. And their tracks have to be threaded, foot-by-foot, across a landscape which is overflowing with red tape and jurisdictions and NIMBY's and existing infrastructure. Said threading to be planned by yet more politicians and bureaucrats and planners, then done by America's low-functioning construction industry.
Nations with good high-speed rail systems have quite different priorities and local governance structures than America.
Hmm true but Europe has most of the same red-tape/NIMBY/environmental impact studies etc issues as America. Those are not unique.
However considering climate impact it pays itself back.
It's 3000 miles! I would personally love to live in a world where you can go 200mph on a train and do it in 15 hours but I wouldn't call it easy.
The current track alignment is not conducive to high speed travel, and CT as a state has no interest in supporting a new alignment that is conducive because they would likely get _negative_ value out of it: as it stands, Acela trains pretty much all stop in New Haven and Stamford: why wouldn't they?
If you go with a high speed link that aims to speed up Boston <> New York travel, it's more likely that you have trains that skip those stops, because additional stops are much more expensive for HSR from a speeding up and slowing down perspective, from a percentage of time added to trip perspective, and for an inefficient alignment perspective.
In my view this is kind of a microcosm of the political problems of the geographically small states of the north east: states like CT/RI/DE especially have very narrow and niche concerns but because of their geographical position have effective veto power over regionally important things like "how expensive are the tolls to drive between New York and DC?" and "can you have HSR between new york and boston?"
Which is why proposals to route it via Long Island and building a 16-mile tunnel under Long Island Sound get consideration.
In other countries like Germany, France and Spain the high-speed network works like a dream though. Though the good stuff is all nationally focused.
The German railway network (including the high-speed part of it) has loads of issues, and it's hardly working like a dream. That said, the interconnect between large cities is pretty great when it works. For these intermediate distances (around 500 km) it's about as fast as flying would be once you factor in getting to/from the airport (vs the more central train station), being there early etc; and much faster than driving by car.
Well, yes and no. Most of it goes through the 'green heart' of the most populated area. There's mostly farms there. The route also goes mostly along existing highways and train tracks so it was just a matter of widening the infrastructure zones that were already there. Holland is very planified so usually these things are already taken into consideration. We don't build housing right besides infrastructure anymore.
However, the environmental red tape is pretty heavy these days. The whole country is at a standstill (house building, traffic, farming) due to limits of nitrogen deposits being exceeded.
So I think it was more that than actual infringements on people's living space. Some tunnels and overpasses were made, yes. Those are the ones that are falling apart already after 10 years :')
Amtrak Cascades is very popular for trips to Seattle.
That is to say.. people will take trains as long as they're truthfully better. We should work on making them better. Even the lovely people of Portland, as concerned as we are about the environment, don't take the train out of the goodness of their hearts.
It takes about the same amount of CO2 to carry container across the Pacific as to truck it across the country. Producing it here or there doesn't make much difference. If anything, it is more efficient to produce in China cause they have higher percent of renewable electricity.
[1] https://www.epa.gov/greenvehicles/greenhouse-gas-emissions-t....