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Nice article. Cement’s climate footprint is really big though, so we should be using it in construction much less than we’re doing now. Glulam is the future.
by jstsch 7y ago
Nice article. Cement’s climate footprint is really big though, so we should be using it in construction much less than we’re doing now. Glulam is the future.
- notelonmusk 7y agohttps://news.ycombinator.com/item?id=21438792 https://news.ycombinator.com/item?id=21438792
- rapnie 7y agoAlso see Sand Wars documentary (recently aired on Al Jazeera) https://en.wikipedia.org/wiki/Sand_Wars https://en.wikipedia.org/wiki/Sand_Wars
- twothamendment 7y agoGluelam and CLT (cross laminated timber) could be used in so many places. I live in an area where trees are like weeds, but the logging industry is nearly dead because "we can't cut down the trees!!!". So, environmentalists, which will it be? Concrete or trees? We have to build with something...
- XorNot 7y agoPlantation grown timber is a very different proposition compared to logging an old-growth forest. Frankly you don't have as many trees around you as you think you do (and you're probably a lot more dependent on them then you realize since local forests are usually performing an important ground support function in preventing hillsides washing away in the rain). No environmentalist is opposing sustainable plantation timber operations, and there's plenty of those going on everywhere.
- maxerickson 7y agoIf they live in the US they probably don't live near much old growth forest. For instance, nearly all of Michigan was logged. Someone driving through the state might not think so, but most of the trees here grew back after that.
- klyrs 7y agoOTOH a disturbing amount of oldgrowth is being harvested in Canada to this day
- twothamendment 7y agoFrankly, you shouldn't assume you know how many trees are around me. Plantation grown and old growth are very different. Just because it is a forest doesn't mean it is old growth. I have a lot of trees and the State land next to me has even more that need thinned. I've thinned out my land for better forest health, better wildlife habitat and to reduce fire danger. The State would do well to do the same, but I is very hard to log anything but private land around here. What happened to my logs? They went to a mill and some for pulp. They weren't old growth, that was gone long ago, but new products like CLT can make use of smaller trees. Plantations are great, but this whole county grows trees like crazy. It isn't hard to look around and find something that can be logged in a response way, but getting approval is near impossible.
- XorNot 7y agoAn industrial logging operation fells and transports about 4 trees an hour. Let's assume about 5 productive hours in a day which is on the conservative side. So 20 trees per day. 100 per week. 1200 every 3 months. Taking a reasonably dense plantation size (which we can assume is close to optimal these days) we get 620 trees per acre (https://www.forest2market.com/blog/how-many-tons-of-wood-are-on-an-acre-of-land https://www.forest2market.com/blog/how-many-tons-of-wood-are...). So a single commercial logging operation is going to be able to clear cut 2 acres of dense forest every 3 months - which will then be just gone and not coming back with any type of biodiversity or wild life for at least 10 years probably longer if ever since we're not talking plantation growth here. You don't have as many trees as you think.
- fiter 7y ago1 square mile is 640 acres. At 8 acres per year, this is 80 years to get back to the beginning! I would have expected that commercial logging is much faster because 8 acres is not much!
- maxerickson 7y agoThey go much faster than 1 tree every 15 minutes. It will of course vary based on the terrain and size of the trees, but watch how modern operations work: https://www.youtube.com/watch?v=GLx9HtKJI_0 https://www.youtube.com/watch?v=GLx9HtKJI_0
- jasoncrawford 7y agoHow does engineered wood do on strength and fire resistance? Would appreciate any unbiased comparisons vs. steel and concrete on those points
- twothamendment 7y agoThat is something I've wondered too. I imagine foundations, elevator shafts and other key parts might still be concrete. Buildings like this are fascinating: https://www.dezeen.com/2019/03/19/mjostarne-worlds-tallest-timber-tower-voll-arkitekter-norway/ https://www.dezeen.com/2019/03/19/mjostarne-worlds-tallest-t...
- rapnie 7y agoElevator shafts can be made with CLT too, like for the 9 storey Murray Grove in London built in 2009 http://waughthistleton.com/murray-grove/ http://waughthistleton.com/murray-grove/
- fiter 7y agoBurned wood acts as insulation for the unburned core so large timbers can have long fire ratings. The rule of thumb is 1.5" per hour. [0] I can’t comment on reinforced concrete, but structural steel requires protection to meet 1+ hour fire ratings. [0] https://www.nishkian.com/fire-rated-wood-construction/ https://www.nishkian.com/fire-rated-wood-construction/
- jedimastert 7y ago>Gluelam and CLT (cross laminated timber) I just looked up some picture. Is it just plywood and OSB with 2x4s? It seems so simple.
- dharma1 7y agoI think trees are a fantastic building material. If left to rot in nature, much of the carbon will slowly be released back to the atmosphere. The carbon sequestering abilities of trees also slow down after a certain age. Now this doesn't mean we should clear-cut old forests, or only have short-lived commercial forests. I think we should aim to have mostly natural forests with trees of different ages, up to hundreds of years, and use selective logging instead of clear cutting. Timber buildings can last hundreds of years. In such buildings, using timber is a great carbon sink. Interestingly, it's the glue that will deteriorate before timber does.
- mannykannot 7y agoI was surprised to see that the lime cycle itself is carbon-neutral, if I am reading it correctly. Is cement's footprint due to the energy required to make it? Or is the chemistry of portland cement not carbon-neutral?
- maxerickson 7y agoYeah, you gotta dig the stuff up, heat it to high temperatures and then ship it to where it is used.
- umvi 7y agoDig it with electric mining tools, heat it with a solar furnace, and ship it with electric trucks?
- catalogia 7y agoMaybe, but that's not how it's done today, and it's not the sort of thing you change overnight. Complicating matters is the fly ash component of modern concrete. Fly ash can replace 50% or more of the portland cement in concrete. Fly ash is a byproduct of burning coal. So when you replace the coal plants with solar arrays, you need to create even more portland cement than you would need to if you were burning coal (and using the subsequent fly ash in your concrete.)
- newnewpdro 7y agoI've read that kilns used to produce the clinker are often fueled by burning waste like used car tires. Wikipedia speaks to it a bit: https://en.wikipedia.org/wiki/Cement_kiln#Alternative_fuels https://en.wikipedia.org/wiki/Cement_kiln#Alternative_fuels
- jasoncrawford 7y agoBoth. See the followup here: https://rootsofprogress.org/cement-redux https://rootsofprogress.org/cement-redux
- kragen 7y ago