So as it says. Solarpunk roads. What are we making them out of? The busses and trams and bikes need something smooth yet with good friction and durability to go over. What it is currently made of, bitumen and asphalt is obtained through the fractional distillation of crude oil.
We can’t get crude oil out the ground without the temptation of taking the other parts for fuel, since we can’t put it back and no-one really wants to be storing unsupervised, highly viscous and flammable components indefinitely. Bitumen has a decently high recycling rate 90-100%, but over time, small amounts of new bitumen are needed, especially if you’re recycling roof tiles. They will be worn down slightly less by trams and busses due to purely lower levels of traffic. Still, there will come a time when there is not enough to make new roads / transport systems or resurface old ones.
And here’s the other thing. The power source of the future is a hydrogen cell battery… Which produces water. Either it gets let out of the car to water areas as it goes or it gets stored. And rain, so it’s a good idea to let the water soak in to reduce flooding or be drained away into green grey water storage systems, where the heavy metals can be soaked up by plants (EDIT: the plants bit could be part of some phytomining system.) and water can stay in the environment to keep it green.
I’m guessing either some kind of porous rock like clay, well-drained types of firm soil or something. Maybe we can press algae or fungus into paving stones so they’re biodegradable. (Especially since algae can be used to suck carbon out of the atmosphere and microplastics from the water, so keeping it stored somewhere is of interest.) Idk. This is a very small problem that can wait a few decades, minimum, so it’s not urgent. Anyone have any ideas / have any material on ideas?
"The power source of the future is a hydrogen cell battery"
I know this wasn't the point of your post, but this statement is just flat wrong. Hydrogen isn't a power source, it's are a power storage medium, and it has an incredible list of disadvantages that are disqualifying. Anyone pushing hydrogen fuel is either a fossil fuel shell or a victim of fossil fuel propaganda.
Blacktop roads should last a lot longer if there were fewer/no heavy vehicles on them, so just getting everyone into bikes, busses, and trams is very helpful. Moving more freight by rail is also helpful, and of course moving less stuff generally is very helpful.
But for those times that a road is needed and must be resurfaced, I'm fond of the idea of a computer-controlled water jet cutting up old concrete from buildings, like walls and foundation, into a half dozen standard shapes that can be laid down easily by robots to create a paved surface. We have a lot of buildings tghat were built in silly places, or were built 70 years ago and designed to last 50, that need to be demolished. That concrete could be cut up and stacked in a storage yard until paving is needed.
Old concetrate buildings that's cannot be modernized are already recycable - to aggregate. You can use to build new thing's, from surface hardening to concrete additives. Besides, in my country, the oldest concrete apartment buildings are 70 years old and have been modernized. New windows, insulation, heat pumps, and solar panels , they will last another 50 years.
Apartments complexes, groups of buildings, and individual blocks of flats operate (relatively) efficiently because they are managed by cooperatives of apartments owners or owners/city.
Oh, the water can be reused fairly easily. Collect it, run it through a settling tank, maybe add a flocculant depending on what you are sawing/tank capacity, and it's good to go again.
There will be a sludge in the settling tank, but it's literally concrete fragments and iron dust/rust from the rebar, nothing super toxic about it.
In no way is a water saw like hydraulic fracturing, which uses a chemical slurry to dissolve or weaken rocks.
Both processes use pressurized water to affect rock, so your statement that they are no way like each other is a little absolute. Fracturing is primarily a pressure-driven mechanical process, like your water saw, not chemical dissolution.
As a general rule, anything that can be made from petroleum can be made from other hydrocarbon sources (ie biomass), it simply requires a lot of energy to be put in. We could almost certainly take sustainably sourced wood, convert it into charcoal, then use a combination of the fischer-tropf process and destructive distillation and have something indistinguishable from mined bitumen at the end, just at a much higher energy cost than mining. I imagine no one has ever done this at scale as it would not be economical, but if it's a critical resource we don't need much of (ie, replacing the bitumen that gets lost through normal recycling) and we have renewable energy to chuck at it it's preferable to the Co2 release, in my view.
For starters, bitumen can be - at least partially - re-used. Road works in the Netherlands scrape off the old surface, reheat it, mix in some new bitumen and put it back down in one pass.
A new highway around Antwerp in Belgium has a textured concrete surface. Now, new concrete does expel a lot of CO2 in manufacturing, so that's not ideal, but it's another option. Recycling concrete is possible as well.
Then there's the option of finding new materials. Bitumen is pretty much the sludge left over after all the more volatile hydrocarbons have been extracted through distillation - it didn't become the defacto tarmac component because it was perfect, but because it was cheap.
For starters, bitumen can be - at least partially - re-use
Asphalt is one of the most extensively recycled materials in the world. You just dig it up, crush, heat and occasionally add a bit more bitumen.
Doesn't matter if there are rocks and dirt and stuff mixed in, that just becomes part of the next layer of asphalt.
I work at a university and saw a student presentation a few years ago about adding crushed glass from recycling centers to concrete. Apparently it lowers the cost of the concrete while increasing hardness and durability. They also claimed that through offsetting a portion of the concrete needed and reducing the processing that's involved in traditional recycling, it makes the concrete carbon negative. I'm not entirely sure I trust their math on that last point, but it would definitely be an improvement.
How does it compare with the usual filler material, like pebbles or gravel?
I'm not against using glass in concrete, but glass can be recycled really well into new glass, so I'm a bit on the fence about using it for something where a less manufacturing-heavy material could be used instead. If they only use glass which can't be recycled (like tempered glass, for instance), then I'm completely on board.
No, this is a misunderstanding about glass. It is cheaper to make new glass than ro recycle old glass because the soda acts as a flux which is similar to a catalyst. That lowers the melt temperature and thereby the cost.
About 50% of the charge is cullet or recycled glass in a typical batch. So you need other uses for the remaining glass and unfortunately, ground glass is hazardous and heavy so economically effective uses are difficult to find. Sealing it in concrete or tar is a valid approach.
I couldn't tell you. This was at least 7 years ago and I'm not an engineer or scientist by any measure. It was just one of the more interesting presentations I've seen at this job.
You're describing a paved street. Works well for low speed roads, not so much for high speed ones. Too wobbly.
However, ideally high speed travel is done by train or tram in the future, and small electric city cars for workers in the city, people that need to move from rural areas to towns for groceries etc. For which paved roads will work just fine.
As long as roller skating rinks still get asphalt or concrete, I think most people will be happy :)
This is an excellent question, and it really gets to how much of our civilization is underpinned by petroleum byproducts that are only cheap because they are produced a long with fuel. Plastic is also produced from petroleum byproducts.
For asphalt/ bitumen, there are a few answers. The least cool answer is simply to keep extracting it from Canadian Tar sands, and instead of torturing the molecules to crack them into gasoline, simply selling them as-is. I'm not sure how economical that is, it is expensive to separate tar from sand and asphalt is cheap.
A cool, carbon negative, solarpunk answer is to cook wood in an anoxic environment, it produces charcoal, synthesis gas for chemical production, and a tarry substance that can be used as asphalt. If the charcoal is used in agriculture as biochar, the process is net carbon negative. Envigas is pursuing this commercially It is a bit challenging because the syngas is hard to store and contains carbon monoxide, so it has to produce three outputs simultaneously. Oil refineries do this with much more complexity, but they have money and experience.
civil engineer here, asphalt is pretty recyclable, not at 100% so new bitumen would be needed in the long term. Alternative is concrete which is pretty carbon intensive. Hope for lower carbon innovations on that front. But yeah, realistically, if you are talking about paving, the thing that's made sense for thousands of years is rocks held in place with some kind of binder, and all the binders that don't suck that we have available today have a carbon footprint
Future communities will be designed to progressively factor out car dependence and factor-in rail use, seeking to consolidate the footprint of the built habitat for sake of relocalized farming, rewilding, and simply reducing our energy overhead. Communities will progressively push them to their peripheries and personal car ownership will become pointless in most places. The general reduction in road use with the general reduction of car use will likely produce a glut of surplus asphalt removed from abandoned suburban roads, parking lots, and eventually highways as they are returned to local farming use and lasting for some time with the much reduced demand before it is phased out.
Cars and trucks will be relegated to local rural use, tend to become smaller as they are locally fabricated, operate at lower speeds, and typically utilitarian in design (think kai trucks/vans) and so many areas may need only enzymatically stabilized dirt roads for these needs, which is already common in rural areas and remote industrial sites. There may be some dispensation in farming communities for letting them run vehicles on their own locally-made biofuels. (methanol, woodgas) Trams/streetcars run on rails and busses will be factored out with other automobiles as, regardless of their energy source, they are less energy-efficient than rail (steel wheels on rail is the most energy-efficient means of ground transportation allowed by known physics) and they still shed a lot of plastic and chemical contaminants from tires and lubricants. (obviously, trams and trains aren't free of this either, but they are better) Lighter, slower, local vehicles will be able to transition to the use of recyclable polyurethane tires, rollers, and 'tweels'.
As asphalt is phased out, heavy road vehicles obsolesced, and with much less road surface to maintain, walkable communities will be able to employ alternatives like block and tile street surfaces and new carbonless materials like geopolymers. This will also facilitate the use of permeable surfaces and devices such as integral solar thermal, photovoltaic, and perhaps piezoelectric energy systems, snow/ice clearing and cleaning, municipal irrigation systems for urban horticulture, and in-street lighting and sensors.
Hydrogen fuel cells are probably not a general energy technology of the future and more likely a part of stationary large scale municipal energy systems and see use in long distance train lines and large ships. Hydrogen is a bulky, complicated, way of storing renewable energy for mobile systems (which is why we may never see hydrogen airliners, their operational economies of scale marginally sustainable already) and most other energy packaging mediums --like hydrogen 'sponge' alloys, hydrides, ammonia, redox solutions-- have similar issues or trade-offs. With the reliance on rail, and with most renewable energy produced as electricity, it is most efficient to transport this energy by catenary lines --a century-old technology that is very well developed. Meanwhile, the smaller and lighter 'last mile' mobility vehicles will do fine with human and battery/supercapacitor power. And this is why we also talk about airships which, for all their trade-offs, can still travel at least twice the speed of surface ships with indefinite range using their own photovoltaic power.
The contemporary sprawl, that was facilitated/ forced by automobiles was a mistake (of capitalist greed / sabotage of the electric streetcar and railroad) that solarpunk should seek to resolve in its long term goals. We should return to rail-based transportation and reduce sprawl through TODs (transit oriented development). For example, an ATN (automated transit network) / PRT (personal rapid transit) could be constructed between primary hubs (large cities) and develop housing and town-scale spurs off them in a more linear (built in series along the main transit corridor) to eliminate traditional automobile-based street designs and rely on local public transit options that could also be rail-based. The whole system could be automated and move people and materials (including parcel delivery) eliminating the need for trucks and cars and related infrastructure (the oil-based infrastructure)
Bitumen also naturally burps out of the ground in various parts of the world in natural tar pits, such as the La Brea pits in Southern California. However, the quantity needed for paving all the roads in the manner we currently pave almost certainly cannot be supplied by merely natural tar pits.
Idea. So wind turbines have blades made of fibreglass which are hard to recycle. We could cut slabs out of fibreglass and sand it down to pave new roads. Not a great solution, but it is reusing.
So roads made of fibre-reinforced plastic dust? Doesn't sound ideal. Realistically we are mot stopping oil overnight, and bitumen is a low-grade waste product. There will be multitudes of more complicated problems to solve before this one.
It does not have the strength of aluminum and steel in the application you are proposing. Composite materials take advantage of stress along the direction of fibers being very well translated. Compressive applications are the exact opposite of what you should do with these composites, think about the carbon fiber submarine that crushed lol.
We will need some oil for other materials, bitumin is just byproduct of rafination.
Second, bitumin roads are VERY easy for recycle, you can remove old pavment, mix it with some new material and lay new pavment - with one machine!
"sustainable" means "we did the math, what's efficient and don't stress environment".
Without math its just virtue signaling and wasting work and resources for little effect.
Composite roads are a terrible idea for a multitude of reasons. First of all it’s straight microplastics, second is that when they break drown from sun exposure and wear your essentialist left with a bunch of exposed needles that implant themselves in people and animals with bad health risks, and this is just they the magnitude of fiberglass required is multiple times what we could possibly provide.
Not all reusing is good, it’s like saying let’s recycle asbestos- cause like they are LITERALLY BOTH FIBERGLASS.
Also addressing another comment you had, no, fiberglass is NOT as strong as aluminum and steel. It has good tensile strength that is predictable (pull direction) - and for that is great, it’s also light as you know.
However in compression (ie: a road) it is very unpredictable and subject to abrupt failure.
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