One thing that human space exploration/settlement teaches us more than anything is how to do everything without net carbon emissions. Solar power? Nuclear power? Both essential to and pioneered in part by space exploration. Same for fuel cell tech. On the International Space Station, CO2 is sucked from the cabin air, combined with hydrogen (produced as a byproduct of producing oxygen by splitting water, much of which was recycled from the air and waste water and urine) to make methane and more water.
ISS also is getting a plastic recycling machine that will be used to 3D print replacement parts from plastic waste and old parts.
Human spaceflight is like the Sustainability Olympics.
Aren't CO2 scrubbers chemically based in ways that would never scale? Like the real Olympics, running marathons is a fairly inefficient way to transport people. P
You'd expect a device built for a space station to scale on the ground? The basic fundamental research is there, that's the main benefit of NASA and publicly funded space exploration. Their innovations may or may not scale, that's up to entrepeneurs who try to figure out a way to scale them.
Right, some nice inventions are due to space race but just after two giant boosters worth of propergol were burnt. And making those things that go to space are not completely carbon neutral either.
Rockets seem like giant greenhouse gas emitters because they burn a lot of fuel in a short time. But it turns out, they're actually comparable with airplanes.
Random googling gives following two figures to compare:
"A jumbo jet (Boeing 747-400) flying from London to New York burns approximately 70,000 kilograms of fuel"[0]
Falcon 9 Full Thrust - Takeoff mass (tonnes) 549, Payload to LEO (kg) (from Cape Canaveral) 22,800 (expendable)[1]
So, roughly 70 metric tons of fuel for a London->New York flight, vs. 500 metric tons for a LEO launch. It's quite comparable. Now consider that there's five orders of magnitude more flights than there's rocket launches[2]. Even if you take an order of magnitude off that to account for most flights being shorter than LHR->JFK, you still end up with space launches barely registering. And then some rocket fuels are non-carbon-emitting.
A few things to bear in mind here. The payload of a rocket is far less of that of a 747, so you aren't remotely comparing like-with-like. Unlike planes rockets aren't typically reused, the energy cost of manufacturing is considerable. (SpaceX's reusable first stages are impressive, but there is a fuel and payload cost.) Finally, taking a flight is about the highest carbon-emitting activity we do - one transatlantic trip is roughly equivalent to driving a car for a year.
Agreed. Thank you for adding this, to paint a fuller picture.
Space industry definitely isn't emissions-free, but right now it doesn't even register. We might have a problem in the future, but there's hope in switching to cleaner fuels planetside and eventually sourcing fuel for space operations from space. As it is today, in my opinion space industry has very good value proposition in terms of utility/carbon emitted.
The 747’s net cargo of passengers plus luggage probability amounts to around 300-400 lb per passenger. 22,800 / 400 ~= 57 passanger equivalent to 22,800 / 300 ~= 76 passanger equivalents.
Further people take much longer trips than your benchmark getting them even closer.
The 500 ton figure also includes the oxidizer which contain no carbon. The equivalent of a plane's jetfuel, RP-1, in a current Falcon 9 is just 123+32=155 metric tons [1].
> "A jumbo jet (Boeing 747-400) flying from London to New York burns approximately 70,000 kilograms of fuel"[0]
If numbers like this were regularly given to laypeople, the climate change discussion situation would be much better. That number for a single flight is ENORMOUS!
It's 2-3 tons carbon emitted per person, per flight. One flight like that would be approx. a quarter of the average carbon usually emitted per person. Shorter flights are much less efficient as a large chunk of fuel is used to simply take off.
Perhaps it's better to restrict oneself to flying OR driving that kind of distance. And it adds up - if you drive: do you ever look at your total mileage, then calculate your carbon emissions?
You are off by a few orders of magnitude. Total fuel load is 70,000kg and a 747-400 carries 416 passengers in a typical 3-class configuration[0]. That comes to only 168kg/passenger.
"For many people reading this, air travel is their most serious environmental sin. One round-trip flight from New York to Europe or to San Francisco creates a warming effect equivalent to 2 or 3 tons of carbon dioxide per person. The average American generates about 19 tons of carbon dioxide a year; the average European, 10."
Seems like there's some tricky math going on, notice: "equivalent" in the above quote:
This calculates 180 kg CO2/hour per passenger. So 8 hours or so between NYC and Paris? 1,440 kg. 1.6 tons. Not quite a few orders of magnitude.
Once through all the calculations, the above then states,
"The CO2 emissions are therefore rounded up and the Carbon Independent calculator takes a values of 250 kg i.e. ¼ tonne CO2 equivalent per hour flying."
No idea what they mean by "Equivalent" either, I was just doing the math with the figures quotes up-thread.
Look at the correction at the bottom of the NYT piece:
> "A news analysis article last Sunday about the impact of air travel on global warming referred imprecisely to the environmental impact of one round-trip flight from New York to Europe or to San Francisco. It has a warming effect equivalent to 2 or 3 tons of carbon dioxide per person, but does not generate that much carbon dioxide per person. (The estimate also includes warming from other greenhouses gases.)"
So actual carbon output per person was correctly calculated, but there is some "carbon equivalent" multiplier slapped on other gasses that brings their totals up from 170kg/px to 2-3T/px.
No, but it's not inconceivable to consider electric cars and biofuel powered jets. It's certainly possible to go mostly carbon neutral on our major transportation systems, but it's a lot of work.
Some common carbonless rocket fuels are hydrogen, hydrazine, and aluminum in solid rockets (boosters; ICBMs).
That said, they usually have an even larger CO2 footprint because processes used to make them take natural gas an an input, or use lots of electricity mostly coming from fossil fuels. The main reasons they're chosen are for their specific impulse (hydrogen) or long-term stability and readiness (solid fuel in ICBMs), rather than their CO2 emissions.
Combustion is exothermic oxidization; that's something completely unrelated to carbon. E.g. hydrogen burns in presence of oxygen, releasing water. Or magnesium burns into magnesium oxide. It so happens that most of the fuels we burn have carbon in them, but that's not a requirement.
That's a little thing that they tell you in high school chemistry classes (remember "reduction–oxidation reactions", or "redox"?), which you then promptly forget. I only remembered because of an unhealthy interest in home-made rocket propellants :).
> remember "reduction–oxidation reactions", or "redox"?
Clearly no :P Also I realized that, unless I have a specific problem I need to solve, I don't remember or like reading about things. I have been taught things in school/uni that I thought were terribly boring and was bad at, until I needed to solve a problem with that information and then I had to re-learn everything. Kind of a waste of time, but I can't change my brain!
By oxidizing something other than carbon, e.g. hydrogen. (Keep in mind that this is similar to calling EVs "zero emission": the vehicle itself does not emit carbon, but providing the energy source of course does; making hydrogen doesn't exactly have low energy demand).
Some hypergolic fuels don't even contain any carbon. For example, hydrazine and nitrogen tetroxide. Mostly what you're interested in rocket fuel is an oxidizer and lots of hydrogen.
The highest performing rocket propellants in common use are hydrogen and oxygen, whose product is water. And NASA and others are working on ways to refuel those using just electricity and water.
> The highest performing rocket propellants in common use are hydrogen and oxygen, whose product is water.
Citation needed. Hydrolox has the highest Isp, but for a boost stage, that alone at all costs is not the most important quality. Hydrolox engines, tanks and piping all needs to be much larger and heavier than other fuels, and in practice, this eats the gains that the higher Isp buys you and more.
It's not an accident that basically all the new engine designs, by multiple different companies, have tested hydrolox and then switched to methalox.
Oh, that is a valid point. Dry mass is just as important as exhaust velocity (Isp). However, I should point out that it's easier to make progress in improving dry mass than it is to improve Isp, so as materials and structural technology improves, hydrolox continues to look better.
Additionally: operating oxygen-rich causes the bulk density of hydrolox to improve dramatically. This is relevant for first stages, and if reusable launch vehicles become so cheap that propellant cost becomes a major constraint, then I should point out that liquid oxygen is practically free: less than $100 per ton.
For first stages, you're right (unless you get clever and are able to solve the engineering challenges of running oxygen-rich). For upper stages, hydrolox again looks very attractive (because a first-order optimization shows that it's energetically favorable to use higher Isp on the upper stage than the lower stage if you need to make a choice... of course, commonality of stages is also desirable at lower flight rates).
> so as materials and structural technology improves, hydrolox continues to look better.
The opposite is true. The relevant problem of hydrogen is that it readily leaks through thin walls. This means that as methalox rockets move to ever thinner composite tanks made of better materials, hydrolox really cannot do better than the current state of the art.
> operating oxygen-rich causes the bulk density of hydrolox to improve dramatically.
True. But it also makes your exhaust into a hot, oxidizing torch, meaning you need much more durable (and heavier!) engine bells.
> For upper stages, hydrolox again looks very attractive
The other problem is that it must be cooled much deeper, and takes much less energy to boil off, making long term storage a hard problem. This makes hydrolox less interesting for any upper stages/manouvering engines that do anything more complex than deliver cargo to earth orbit. Once you add long coast times, it gets really bad -- to the point that the SLS moon missions actually get lower efficiency from their upper stages than they would get from kerolox, once you account for the extra hydrogen they have to ferry up just to let it boil away.
> commonality of stages is also desirable at lower flight rates
Commonality of stages is desirable at all flight rates. Paying for the highest possible efficiency gadget for every task is one of the reasons old space has such huge problems competing in cost with the new entries. Just having a little more thrust and burning a little more fuel is more cost-efficient than having another engine manufacturing line.
Methalox engines will probably power almost everything newly designed going forward. Not because they are the best solution for anything, but because they are 90% there at everything, while lacking the worst problems of everything. Their fuel is easy to contain and stable for long-term storage, they have no carbon build up in the exhaust, their exhaust is reasonably cool and not heavily corroding, and they have enough thrust and enough of Isp that these advantages will outweigh a minor efficiency loss in almost all situations.
The winds of the industry have shifted, and now that methane has been proven, no new hydrolox engines are being developed, with basically everyone choosing methalox for new designs instead. JSC Kuznetsov, SpaceX, BO, ESA and Landspace all independently made the same choice. Others have chosen to use engines developed by some of them. The end result is that the only major rocket operators still developing a future rocket with non-methalox engines are:
- Roscosmos (The Angara rocket family development was started before methalox was seen as viable. There are future plans for switching propellants, but afaik no funding for them currently.)
- Arianespace (The Ariane 6 development was started before methalox was proven. Ariane NEXT is going to run on methane.)
- NASA (SLS was mandated to use existing engine designs by the senate, because the senators' home states needed the money.)
Your points about hydrogen leaking are not actually accurate. This doesn't negate the advantages at all, and as vehicles get larger, the advantages become even more pronounced. Oxygen-rich is used on Russian engines, which are some of the best engines ever made (although they haven't improved on them much in the last couple decades).
Commonality of stages is more important at lower flight rates since you have to pay for amortization of the greater development costs.
I like methane/oxygen. It is a very good choice. But I also don't buy into the hydrolox phobia that has become popular. Hydrolox is still a very good choice.
(I think that SpaceX and Blue Origin are completely right for picking methane/oxygen for BFR and New Glenn; I'm speaking even more long-term...)
The coal used by most countries for producing electricity is not that clean though.
If anyone is really serious about global warming, shutting down coal plants should be priority 1, natural gas plants priority 2 and transportation emissions priority 3.
Fortunately we can work in parallel. Switching anything from burning whatever it's burning to electricity is a huge win, because electricity sources can be changed independently of electricity consumers. Today's electric cars powered by coal are tomorrow's electric cars powered by solar, wind and nuclear, with no involvement of the car owners required.
Transportation is really #2 after coal. Transportation is responsible for the majority of emissions in the US, and although an EV running on coal is basically just breaking even for GHG emissions, an EV running on natural gas is a signficant net-win for GHG emissions.
In the US using the average electricity mix, an EV like the Model 3 emits a factor of 2.5x less GHG than an equivalent diesel vehicle. Because 40% of electricity is from clean sources (nuclear, wind, hydro, solar, geothermal), and coal is just 27% now.
I put natural gas as #2 mostly as a hedge against just replacing coal with NG.
As for moving transportation to electrical propulsion, the real effect has to be judged by the marginal effect it has on emissions. If the marginal change is covered by coal, the benefit is much smaller than if the marginal change is covered by clean sources.
Nuclear power is primarily a byproduct of nuclear weapons - that's why virtually all reactors use a Uranium -> Plutonium cycle. The only space influence was radiothermal generators, which are a bit niche.
Niche yes, but also quite an advancement at the time. You can have many more lighthouses and relays if you don't need to supply diesel every few weeks and have an engineer repair engines.
counter points:
if you put all the space program innovation and money to sustainability, there would be not problems on that area anymore already... the technologies they have brought us could have been invented at only a fraction of the cost. https://en.wikipedia.org/wiki/Budget_of_NASA
nuclear power was not at all pioneered by the space exploration... it was pioneered by people trying to destroy other humans. the first nuclear reactor was not for power electrically, but to breed plutonium for bombs. https://en.wikipedia.org/wiki/Nuclear_power
human spaceflight is a void where intelligence and resources disappear into
Spaceflight is wasteful because it is designed to be. The same military purposes you talk about is what causes companies like ULA to exist. The space shuttle ended up being an industrial jobs program that resulted in huge costs for every launch.
On the other side, NASA is nowadays quite efficient with their money. And companies like SpaceX showed how costs can be tremendously decreased.
Excerpt: "NASA had offered a quarter-million-dollar prize to the first research team that could figure out how to extract oxygen from the moon’s surface, a precondition for establishing lunar bases. Sadoway proposed using an electrolytic cell—which produces an electric current to break down compounds—to extract oxygen from lunar rocks. The by-product was molten metal, a realization that led him to explore the possibility of using a similar approach to process metals back on Earth."
Two for the price of one! (Well, potential solutions to problems that is! One, how to generate oxygen on other planets, and two, how to smelt metals on this one while generating less carbon emissions. Well played!)
Interestingly, this is exactly the process used in Andy Weir's new novel Artemis and makes oxygen the least of the problems of the moon city that the novel is named after.
Government intervention. Not good. Much better would be letting free markets to allocate more resources to figure out how to get people clicking more ads and development of cryptocurrencies.
Has the government "subsidized" SpaceX? AFAIK the government has been a consistent customer of SpaceX and they've leased facilities from NASA but it seems that overall they aren't being subsidized but rather patronized.
You are aware than the government pays SpaceX more than market price right? The difference is itemized as "additional checks", but it's subsidies in anything but name.
It's not just metals you can smelt, you can also smelt silicon from rocks. It ends up in a melt of iron and silicon, but one could potentially separate out the silicon and use it to make solar cells.[0] Which can then be used to power more electrolysis units to make more solar cells.
[0]https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/200501...
Until the product is actually built and tested at commercial scale, it’s too early to say how well or affordably it will really work.
Moreover, merely producing a green version of a product for around the same price won’t be enough to transform the industry, given the billions of dollars in sunk costs in steel mills that can operate for decades.
Even if the perfect technology came on the scene today, it’d probably be several decades before we could effectively transition to it
Talk about playing the long game...
I wonder how much cheaper their method would need to be, given the above.
Would it be faster/cheaper to develop perfect scrubbers to retrofit onto existing mills? (Funded through donations, and/or to sell to offset carbon taxes.)
Still good to have this new technology available to transition to down the line.
I read a retrospective paper by a Norwegian group that worked on electrowinning iron from mixed sulfide ores. Taking iron sulfide waste and converting it to sulfuric acid and iron sheet. I think they were getting 4.25kwh per kg. Nop idea if that is good or not but at $0.15/kwh that's $640/ton.
I thought about that over the last few years because it's aqueous process so should be able to run intermittently.
Energy prices are going to be key here. The mistake would be assuming they are a constant though. They've been trending down and lately coal has been considered on the expensive end of the spectrum. Those prices have been trending down due to clean energy prices dropping. Both solar and wind are now winning bids on price that used to go to coal plants. Also as coal plants shut down and coal mines are closed, coal might actually get more hard to get (i.e. more expensive). Some recent solar plants are delivering power well below the prices you cite (I've heard prices going as low as 3-4 cents/kWh).
I could imagine most steel plants are big enough that they'd want their own infrastructure in any case. So, for a future steel plant based on this stuff with its own cheap energy supply, it might end up being cheaper and cleaner. That could end up being really disruptive.
It doesn't have to turn a profit, it just has to lose less money than it costs to dump the waste products it's made out of. Depending on how regulated that becomes, it might be worthwhile in the future.
That's probably slabs of billet: unprocessed steel right from the mill. Not cold rolled bars or rods, or sheet.
I only know a little about steel prices from being a hobby machinist, but I know a bit more about hay prices. For the price of a cheap laptop, you can get two tons of hay delivered :-)
There are other tests as well. the Hybrit method that will be
going through a pilot phase starting this year. Fossil free steel making. Still some issues to solve but it is still interesting
The steel industry isn't really as "conservative" as is being portrayed here. In the past 30 years, the amount of recycled metal being used has skyrocketed, and entire companies have come to power because of it. Sure, big old U.S. Steel is behind the times, but that's true for any industry.
> Sure, big old U.S. Steel is behind the times, but that's true for any industry.
U.S. Steel operates integrated mills, which make steel from raw materials. "Mini-mills" make steel using electric arc blast furnaces to recycle existing steel.
If you need very high quality steel, you have to get it from an integrated mill. Everyone else can use the recycled stuff. The real benefit that you are talking about is the fact that recycled steel quality is improving enough to be useful in more applications.
PS - U.S. Steel is converting their Alabama mill to an electric arc blast furnace (they may have finished by now).
TL;DR: This is a well known technique, but isn't used because the economics don't work out.
This technique looks nearly identical to the technique used to make aluminium from aluminium oxide.
The only difference is it needs to happen much hotter (1500C vs 700C).
The process uses a lot of electricity, so much that it is the main cost of aluminium production.
The process, when used in steelmaking, would use 824.2 kJ/mol of iron(III) oxide, producing 111.6 g/mol of iron. That works out to 7.42 kJ / g, or 2 kwh per kilogram of steel. Price varies widely worldwide, but with the cheapest electricity in europe that works out to about $0.10.[1]
Thats lots of electricity for the refining process, and it seems likley that 0.7kg of coal [2] works out far far cheaper at $0.05 [3].
Looking into those calculations, I see the current average energy used to make 1 kg of steel is about 10 thousand BTU [1] - about 3 kWh. 75% is consumed in blast furnace and "About 50% of an integrated facility’s energy input comes from coal, 35% from electricity, 5% from natural gas and 5% from other gasses [2]"
Your estimate of 2kWh per kilo would look very promising for this process. Also the comparison of electrical price, with the price for raw coal surely begs some adjustment.
*Not including the time required to retool the entire Earth's iron smelters into electrolytic smelters and build out associated electric infrastructure needed to accompany the exponential increase of a country's energy intake.
That's spinning too hard in the other direction. This is a technique for smelting. Once smelted and shipped, the metal is always going to be remelted anyway to mix and cast the final alloy. And in fact in the modern world the bulk of this work is done with electricity already in an electric arc furnace.
We're talking about a constant factor on top of a steel industry already very dependent on electrical power, certainly not (sigh) an "exponential increase of a country's energy intake".
"In the main approach to steelmaking today, iron oxide is placed into a blast furnace with coke, a hard, porous substance derived from coal...
This and other steps in the process pump around 1.7 gigatons of carbon dioxide into the atmosphere annually, ... And that’s before taking into account the fuels required to fire the furnaces."
Blast furnaces do not need fuel to create iron, the process in which iron oxide is converted to iron is endothermic but the coke itself is the fuel in the furnace. It actually is necessary to do this to produce carbon monoxide which reacts with the iron oxide.
It can get very complicated. There are a few different reactions which occur in a Blast Furnace some are exothermic some are endothermic.
BF is very simplistically a giant counter current reactor. Ore and Coke (the reactants) are added at the top at room temperature and hot gas (the "blast") is injected at the bottom and they flow past each other.
CO is not the only reductant that plays a role Hydrogen primarily from the humidity contained within injected gas also plays a role in the heat balance of the furnace.
Hydrogen is actually very efficient at reducing iron and avoids the CO2 byproduct. I know in the past some alternative ironmaking methods have looked into using things like hydrogen gas and natural gas (CH4) to directly reduce iron ore using a process abbreviated as DRI (Direct Reduced Iron) and for a while in the '90's this was marketed as a Blast Furnace alternative I haven't really kept up with technology.
I started my career as a Metallurgist (Materials Engineer) working at a Blast Furnace they are hugely complicated beasts.
Blast furnaces need fuel to raise the temperature of the blast furnace input to speed up stripping what becomes slag and the oxygen from the iron oxide in the iron ore. Carbon monoxide is what is able to penetrate the iron ore at the high temperatures.
My previous comment is criticizing the author for suggesting that yet another fuel produces the heat for the blast furnace.
Steel is an alloy of iron and carbon. They mix coke with the iron to add carbon to it. The article is talking about the CO2 released from that coke, and not the coke used to fuel the furnace.
Cast iron contains a high concentration of carbon, which makes it brittle. To make steel you need a heavy oxidizer to extract the (reduced) carbon. This is usually done using a "basic oxygen furnace", which is basically injecting a high pressure, very high velocity stream of oxygen into the metal to game thermodynamics into combusting the carbon without combusting the iron.
The phase diagram is very interesting too. Very little carbon is needed to go from elemental iron to steel, looks like about 0.008%. Thanks for posting that!
The coke that is mixed with the iron ore is the coke that heats the furnace. As the coke (carbon) reacts with oxygen, some of the carbon monoxide then strips oxygen from the iron oxide in the iron ore.
You sound like confused, from my limited knowledge, the making of steel is exactly opposite of what you said, they extract carbon atoms from iron, that makes carbon monoxide into carbon dioxide.
ISS also is getting a plastic recycling machine that will be used to 3D print replacement parts from plastic waste and old parts.
Human spaceflight is like the Sustainability Olympics.