A loosely moderated place to ask open-ended questions
If your post meets the following criteria, it's welcome here!
Looking for support?
Looking for a community?
~Icon~ ~by~ ~@Double_[email protected]~
Bioasphalts can be made from all sorts of non-petroleun renewable resources, including food wastes and sewerage effluent: https://en.m.wikipedia.org/wiki/Bioasphalt
I think the main challenge now will be determining the ideal mix of ingredients that best suit the purpose of the asphalt.
Good to know! Thanks!
Also another factor is heavy vehicles. I don’t have the article or video, but I remember hearing that a majority of road damage comes from heavy vehicles. I believe the video was also comparing roads to Rome roads where it wasn’t that they were built better (although volcanic ash did help) it’s that horses and people are way less heavy than the 3,000+lb vehicles we have going almost 24/7.
Less road damage would mean less containments/pollution and less need for repair. So the future might be seeing more public transit and more rail transit for materials/products which would mean wherever we need to add more road or re do sections we would replace it with the greener option or potential normal asphalt since it wouldn’t need to be touched for another 20,30,40+ years.
that a majority of road damage comes from heavy vehicles
Specifically, wear and tear on the road surface scales with the fourth power of vehicle weight.
As a worked example, this means that if we compare a 3-ton cargo van and a 1½-ton sedan, the cargo van weighs twice as much as the sedan, but it does sixteen times as much damage to the road.
Axle load, actually. In theory a 1.5-ton car with two axles and a 3-ton truck with four equally loaded axles would cause the same amount of damage. A 1-ton unicycle would cause more damage than the truck.
Note, though, that this is a rule of thumb. A 50-ton tank is still a 50-ton tank even if you manage to make it have fifty tiny axles. But for fairly average motor vehicles under fairly average conditions it's close enough to be useful for planning.
As with all equations in civil engineering, it’s not really derived from physics so much as it’s the curve that best fits the data.
It’s kind of interesting in that way, because it’s an implicit declaration that when shit gets really heavy (pun intended), we trust empirical observations more than we trust our own theories of how things work.
I think it’s a great example of coming back to the roots of science in measurement, as a practical humility we must take seriously because everything civil engineers do is high stakes.
Surely that's damage-per-axle? So it'd be two 1.5-ton cars to match the trucks 4 axles
It could be, but I wouldn’t assume that it is.
I remember when calculating bridge wear, we were discussing the truck arriving on the bridge in terms of impact. It could be the damage somehow comes mostly from the first wheels to encounter the material.
Wow, it makes sense but definitely not good at all
Climate change isn’t caused by just using fossil fuels to make a product, it’s caused by burning fossil fuels releasing greenhouse gasses, (primarily carbon dioxide and methane), into the environment.
Asphalt is a problematic material, but not so much because it’s made from oil. It’s problematic because we burn fossil fuels to harvest the raw crude and to generate the energy needed to refine crude into asphalt. The carbon in the asphalt itself remains sequestered there and doesn’t contribute to the greenhouse effect as long as it isn’t burned later.
If we figured out how to extract crude and generate the vast amount of energy needed to manufacture asphalt without actually burning fossil fuels we’d eliminate the vast majority of asphalt’s impact on climate change.
In fact it’s been shown in a lab that it’s possible to make asphalt from CO2. It’s currently cost prohibitive to do so, but in theory asphalt could be part of the solution to climate change.
Now Asphalt does have other environmental issues, like leaching toxic chemicals into the soil and water table and the fact that it’s usually black which absorbs more the sun’s radiation than almost anything else which would reflect more of the sun’s energy back out into space. But those problems aren’t necessarily solved by using non-petroleum based bioasphault, nor are they unsolvable with bitumen based asphalt.
About 20% of a barrel of oil gets made into products like plastics or foam, that’s not what’s causing climate change. What causing climate change is the 80% that gets refined and burned for cheep energy. So it’s less “Just stop oil” and more “Just stop burning oil”
That's not to mention the reusability of asphalt:
Regarding the circular economy, the data from reporting countries showed that in such countries, 72% of the reclaimed asphalt available for the industry was re-used, 25% recycled and only 3% used on unknown applications or put to landfill.
Thank you for the very detailed answer!
Asphalt is a problematic material, but not so much because it’s made from oil. It’s problematic because we burn fossil fuels to harvest the raw crude and to generate the energy needed to refine crude into asphalt. The carbon in the asphalt itself remains sequestered there and doesn’t contribute to the greenhouse effect as long as it isn’t burned later.
Not to mention the lighter fractions will include things like gasoline, and once you have gasoline it's oh-so-tempting to burn it.
Honestly I doubt the emissions just from heating it in a fractionating tower are all that significant themselves, even if they're not using renewables to do it.
Asphalt is really highly recycled (though I'm sure at a high energy cost), so at least we have that going for us.
It currently takes about 3 to 6 cubic meters of gas to make 1 ton of asphalt. It doesn't really matter if that's new or recycled, and doesn't include mining and transporting the materials.
I do like the brick roads they often have in places like the Netherlands. Example
Not sure how they compare in environmental impact though.
Aren't brick roads bumpy to drive on? It may be fine to put in housing areas where cars drive slow normally, but I imagine it would be a pain in the ass (literally, lol) and dangerous to drive on on high speed roads.
Sure, you wouldn't put them on highways. But I'd like to have less of those anyway. They're decent for cycling or driving at lower speeds.
dunno if I'd call it decent. bumps will wear out suspension components prematurely, meaning they'll have to be replaced more often. so more metal and rubber being produced. is it enough to make brick not worth it? idk. also worth noting that asphalt is far grippier than brick. more grip = safer
I think you really overestimate the bumpiness of those kind of roads. They're not like medieval cobbleroads.
We have all kinds in my city: Medieval cobblestone, brick roads and asphalt. As a cyclist I have to tell you that I hate all kinds of brick roads that I have encountered. Even when they're not the horrible middle age version, they will often get deformed by roots or depression of the ground quite rapidly, making them even more bumpy. For this reason I think, I saw in Sweden in an otherwise bricky city center that they had a narrow asphalt lane on the side of the road for cyclists. I was just amazed that someone would spend that much thought into what's great for cyclists. As a cyclist I really love asphalt :D
Let’s be real here. Asphalt is the result of tens of thousands of years of human decision making, all of it heavily invested in finding the best solution to each problem.
they will often get deformed by roots or depression of the ground quite rapidly
That's true, but more of a maintenance issue IMO. Brick roads do have the advantage that workers can just take some of the bricks out, fix whatever is wrong underneath and put the same bricks back on. Can't really do that with asphalt, which will eventually deform as well.
Asphalt is almost a liquid when it’s hot. That’s a significant advantage in application.
I actually know from watching Formula E, that in order to make their indoor/outdoor track in an exhibition center in London race viable, and would still be able to operate normally after the race, they developed a way to add grip on concrete floors without the use of asphalt.
Article link
YouTube video from Chain Bear on how they made the track
Edit: Link format
...No they are very smooth. I think you are thinking of cobblestones.
Trains
I mean, I'm all for more public transportation (seriously, wtf America?). But in reality, there is still a need for public roads for things like buses in places where subway stations aren't viable, and also for logistics (construction materials, mail, Amazon deliveries, your Uber eats, etc.)
While it's not a full replacement the raw materials making up the road surface can be reduced. Here's an example where books were recycled into the road surface - http://news.bbc.co.uk/1/hi/england/west_midlands/3330245.stm
What ruins the asphalt is the weight of vehicles, and in car-free places, you can see 30+ year old asphalt without potholes or cracks with only minor damage or repairs. If it weren't for the sun making the asphalt pale, you wouldn't know it isn't a recently paved street.
By reducing the number of cars in cities and towns in favour of bicycles and rail, and putting stricter restrictions on the weight of the vehicles, we can make asphalt last WAY longer.
Also, some modern asphalts are more durable than older ones, but I don't know the specifics.
If we eliminate the use of fossil fuel to combat climate change, our agricultural output will drop enormously and a significant fraction of humanity will starve to death.
I think if you‘re driven to find non-fossil road pavement strategies, you should refocus your efforts on finding non-fossil sources of nitrogen for fertilizer.
Food is way more fundamental than roads, and it’s far more heavily reliant on fossil fuels.
Well this thread is a discussion on alternatives and what you think are not talked about enough, so thanks for informing about fertilizers. I certainly didn't know that they were also reliant on fossil fuel.
Your logic doesn't make sense. Reducing the use of fossil fuels in other things leaves more for use of growing food.
Modern farm fertilizers are all made with ammonia which is produced with natural gas. Apparently Yara,a Norwegian company, is trying to replace the fossil fuel with solar power. Source
Of course you could also use manure or compost as fertilizer, but only some of the few small farmers would probably be willing to since it is harder and therefore more costly.
Hmm. Well, the obvious choice would be some kind of tar. Someone mentioned that oil extraction is not as bad if you don't burn it, too. What about a plastic blend?
Extended question: One thing I think of is all the various chemical building blocks that go into synthetic things, like drugs. As I understand it, right now we pull up crude, and then repeatedly process it until we've split it into 1000s of individual component molecules. Pick a chemical, go to the "production" section of the Wikipedia, click on a component and repeat; you'll probably find one.
There's approaches to making individual building blocks green ways, but I don't think there's a fallback for cases where a specific commodity chemical has no alternative. What we really need is a way to make a similar blend of things from pyrolysis of biomass. I assume somebody is working on it.
Roads wear. Plastic dust getting spread everywhere is probably a bad thing.
That's true, but AFAIK asphalt roads don't tend to produce a fine dust (rather, the tires and mufflers do), so there should be some kind of plastic resin that would wear a similar way.
Then we’ve got big chunks of plastic everywhere.
Trouble is that kind of gradual wear pretty much guarantees the material is coming off in tiny chunks that are basically dust.