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Catalytic process with lignin could enable sustainable aviation fuel
- labster 4y agoThis seems like more organic chemistry research, not a giant breakthrough. Still, we need sustainable fuels in aviation for the foreseeable future. Given the physics of flight on this planet, batteries just won’t cut it. Unfortunately even with a 100% renewable fuel, you still have additional greenhouse effect from the condensation trails. I doubt there’s a reasonable way to capture jet exhaust, and even if it did it would increase the weight of the aircraft. So basically, the future is steampunk dirigibles, and don’t let anyone tell ya different.
- dataflow 4y agoI almost didn't believe you that the effect of contrails could be that large, but I searched and it sounds crazy: https://e360.yale.edu/features/how-airplane-contrails-are-helping-make-the-planet-warmer https://e360.yale.edu/features/how-airplane-contrails-are-he...
- edrxty 4y agoFor what it's worth, contrails only form when conditions are right at certain altitudes, so if we had renewable fuels we could theoretically move aircraft outside the contrail altitude window. It would piss off controllers and burn slightly more fuel sometimes but it could be done.
- twoslide 4y agoI believe it's not actually contrails specifically but rather the effects of releasing exhaust (CO2) at a high altitude (which would happen whether the contrails form or not).
- masklinn 4y agoI’m not sure what you’re talking about, but the thread and article are about contrails, specifically.
- someweirdperson 4y agoCO2 is just the basic evil everyone talks about. Water is a lot more evil (much broader range of wave lengths of light absorbed than the comparatively tiny range of CO2), if it is in the air. Water changes it behavior depending on the relative amount in the air. A sufficiently high amount will act on visible light (contrails, clouds, fog, ...), but even in its "transparent" form it messes with wave lengths outside of the visible range. Contrails are created by local changes of temperature at the wing tips (turning the invisible water into visible, temporarily) and by adding water as part of the exhaust. Burning CxHy leaves some H2O, visible or not. I would have guessed that the visible form is contributing more to cooling than the (probably more common) invisble form. Possibly a matter of when they turn invisible, which might be more likely in the morning than at night (those produced during one day staying visible during the night helping with heating but vanishing next day, not helping with cooling). Modelling water properly is quite surely complicated, with bigger effects than CO2. Not only for contrails.
- sokoloff 4y agoContrails are ice from water in the exhaust, unrelated to the wingtips. You will sometimes see vortices at high angles of attack on takeoff or landing, but those don’t turn into contrails.
- ouid 4y ago
- labster 4y agoIt’s true, though. Water causes roughly 30°C of global warming. We can’t get much if any more from water vapor, but there are several positive and negative feedbacks from clouds that are quite interesting. High clouds are ice, which allow transmission of visible light, but absorb in the infrared. Water is to rain as CO2 is to glucose.
- ZeroGravitas 4y agoThis became a minor fake controversy recently when Google changed their carbon footprint measures on flight to stop estimating these non carbon effects. The reason they did so was they were just using a rule of thumb that applies to all flights and they want to be able to encourage airlines to adopt the known practices that can avoid these extra emissions (shifting time of flights is the big one I think). There's no standard yet for estimating them though, but they are working on one: https://airqualitynews.com/2022/09/01/is-google-airbrushing-emissions-data-to-boost-sales/ https://airqualitynews.com/2022/09/01/is-google-airbrushing-...
- abazeeeeeee 4y ago
- jl6 4y agoI guess it’s unintuitive because the contrails only last a few hours, so how could they have any long term effect? But aviation is continuous, so they get replaced quickly, so there’s probably a constant contribution to warming. I’m not sure how the contrail effect interacts with Earth’s increasing cloudiness.
- themitigating 4y agoI want to also say I didn't believe them but because I thought he was referring to the conspiracy theory not the actual water vapor trails
- ghastmaster 4y ago"Chem trails" is the terminology usually associated with the conspiracy theories.
- Schroedingersat 4y ago> I doubt there’s a reasonable way to capture jet exhaust, and even if it did it would increase the weight of the aircraft. Just taking it with you is a non-starter. If your fuel is mostly carbon by weight, then the CO2 will weigh 2-3x as much. At that point batteries are starting to look appealing by comparison. There are battery techs with around 400Wh/kg and various almost-working ideas in the 500-600 region. Once you run 11000Wh/kg hydrocarbons through a turbine at 30% and carry the 2 Oxygen atoms for every C you might only be getting 1000Wh per kg of exhaust you carry.
- myblake 4y agoDoes commercial aviation carry an oxidizer though? I thought jets were air breathing.
- londons_explore 4y agoOP's point is that if they wanted to capture the exhaust, then they would be carrying the oxidizer...
- Schroedingersat 4y agoYou are correct. I was speaking of the exhaust which is oxidised (that is, after all why you burn the fuel). If you wanted to do CCS on a jet the H2O can be vented, but the CO2 (which you have to carry to your destination) weighs 44/12 times the carbon in the fuel (which is a large portion of the fuel mass -- abput 3/4ths iirc).
- shawnb576 4y agoI think the hydrogen-electric [1] development is more promising here because it has the potential to deliver long haul flights with no emissions or contrails. While H2 isn't great for decarbonization at scale, in specific industries like aviation it might be applicable assuming it's made cleanly. [1] https://www.zeroavia.com/ https://www.zeroavia.com/
- Teknoman117 4y agoWhat's the justification to expect that 25-50% of human climate impact will be from aviation by 2050? Growing population? Lower cost of access to flight? Other industries decarbonizing and causing aviation impact to just be a larger fraction of overall impact?
- jabl 4y agoIIRC it's a combination of air travel continuing to expand at the roughly 2.5% yearly rate it has been doing for the past decades, and other sectors of the economy successfully decarbonizing.
- kwhitefoot 4y agoIsn't a contrail a condensation trail? In a hydrogen fuel cell the waste product is H2O so surely there is a contrail.
- cesaref 4y agoI believe contrail formation requires nucleation sites, which is normally provided by soot particles from the burning fuel.
- kwhitefoot 4y agoGood point, thanks.
- labster 4y agoIt doesn’t in a really moist layer. Ice condensation nuclei are relatively rare (thus the silver nitride seeding idea), so a lot of times ice clouds form when a parcel of air gets supersaturated. This is pretty common.
- DrewADesign 4y agoI'm not a subject matter expert, but think much of the value stems from lignin being so abundant because it's a byproduct of paper making rather than some advancement in chemistry, itself.
- deleted 4y ago[deleted]
- abazeeeeeee 4y ago
- once_inc 4y agoWh-Whut? Is that supposed to be six contrails?
- danhor 4y agoThere are indications that SAF burn cleaner and thus produce less than half the contrails: https://www.nasa.gov/press-release/nasa-dlr-study-finds-sustainable-aviation-fuel-can-reduce-contrails https://www.nasa.gov/press-release/nasa-dlr-study-finds-sust... and lowers the effeet on global warming.
- labster 4y agoThis should be the top reply to me. Cool research. I wouldn’t have thought about it (though I did worse in my atmospheric chemistry class than anything else I studied in atmospheric science, so not surprising).
- ZeroGravitas 4y agoBatteries make sense for shorter flight today and will slowly increase their range, future plane designs will likely use hydrogen fuel cells, but yes, for existing planes and the next couple of decades the industry is looking at a range of Sustainable ways to make e-kerosene to burn in existing engines, several of which are at pilot (no pun intended) stages.
- kumarski 4y agoAnyone wanna take a bet that kwh required to create and process a pound of lignin into the desired format exceeds its useful energy output at all low, medium, and high scale?
- danuker 4y agoAdd enough penalties for using fossil fuels, and the market will switch to renewable or synthetic fuels.
- vixen99 4y agoThere's an issue here. 80% of the global sulfur supply comes from removal of sulfur from fossil fuels. Among countless other vital industrial uses without which life as we know it ceases, sulfur is used for making lithium batteries and fertilizer.
- geysersam 4y agoWhat's the issue? Even if oil is the only feasible supply of sulphur, it can still be used for that purpose. Just don't burn it without capturing the exhaust. Obviously this has consequences in form of higher prices. But the alternative leads to global warming.
- catfan 4y ago
- jupp0r 4y agoHow is this a problem? If the energy is gathered via renewables, then why not produce it at 5x the energy it yields when burned airborne?
- ZeroGravitas 4y agoThis would be a problem if it was the kWh of energy that was causing climate change, rather than the carbon. In anything you can electrify, just the electrification cuts energy use by a factor 3 but some things are actually hard to electrify in the short term so cheap green renewables being used to make carbon neutral fuels makes a lot of sense as we have access to lots of cheap energy, and even more as we electrify more and more stuff but have only a limited carbon budget.
- catfan 4y ago
- WalterBright 4y agoI don't get it. The fuel is still a hydrocarbon. Note the "carbon" in hydrocarbon. When it burns it's still emitting CO2. Where the fuel comes from is not relevant to atmospheric CO2. Edit: Let's go through this carefully. 1. pump jet fuel out of the ground. Burn it. CO2 goes into atmosphere. Bury plants with an equivalent amount of C. 2. Convert plants with an equivalent about of C into jet fuel. Burn it. CO2 goes into atmosphere. So, which scenario reduces the amount of CO2 into the atmosphere? Neither. They're the same. This whole scheme of "sustainable biofuels" is a complete Emperor Has No Clothes sham, to put it mildly.
- manmal 4y agoThe plants used for the fuel would have pulled the CO2 from the atmosphere within the last year or so.
- WalterBright 4y agoHow is that relevant? A C atom from a million years ago is the same as a C atom from today. (Yes, I know Carbon 14 decays, but that's not relevant to this discussion.) A C atom from today is not magically different.
- deleted 4y ago[deleted]
- 8organicbits 4y agoThe difference is that carbon from millions of years ago was buried deep underground. Digging up and burning fuel increases atmospheric carbon. Cycling atmospheric carbon into fuel and back to the atmosphere is a one for one replacement.
- WalterBright 4y agoThat's why I wrote burying the equivalent plant C mass, which is a lot cheaper than trying to convert it into fuel.
- lordnacho 4y agoInterestingly lignin is also the thing that caused us to have this whole carbon problem in the first place. When it first evolved there was nothing that could break it down and that's part of the reason why we have all these deposits millions of years later.
- nyanpasu64 4y agohttps://www.pnas.org/doi/10.1073/pnas.1517943113 https://www.pnas.org/doi/10.1073/pnas.1517943113 claims that lignin was being broken down even during coal-forming periods. I did not verify this article though.
- Roark66 4y agoWait what? "lignin underutilised", (used)"only in low-value applications"? If by low value applications they mean individual house heating then perhaps. Could those factories that make wood products and currently dispose of their waste wood(sawdust etc) by selling it to pellet makers make much more by selling it for aviation fuel? I seriously doubt it. The most recently I bought wood pellets I paid about ~$30/GJ aviation fuel(jet a) now appears to be around ~$56/GJ. It is more, but not orders of magnitude more. Add to this the cost of chemicals, reactors, disposal of byproducts and I doubt this new use will provide more profit.
- ZeroGravitas 4y agoI believe there is some kind of black liquid that is a waste product of paper production. I've read a few ideas for reusing this. I think traditionally it's been burnt to power the paper processes. https://en.m.wikipedia.org/wiki/Black_liquor https://en.m.wikipedia.org/wiki/Black_liquor > In the United States, paper companies have consumed nearly all of the black liquor they produce since the 1990s.[6] As a result, the forest products industry has become one of the United States' leading generators of carbon-neutral renewable energy, producing approximately 28.5 terawatt hours of electricity annually. So, assuming those land based processes can be substituted for renewables energy, that frees this up to be used in transport. (And yes this also applies to wood burnt in electricity generation, CHP and home heating. Burning stuff is inefficient, costly and polluting, we should be doing less of it whenever we can. Get a heat pump and some insulation).
- jcynix 4y agoSustainable? Yes, in theory, but no in practise. That's my gut feeling because I doubt that wood (or lignin producers) will grow as fast as our travel (and heating) will use them up. Just skimmed some studies (in German) describing these consequences. And here in Europe there's currently the "trend" to switch from gas heating to pellets (or just wood stoves in private buildings) duento the "energy crisis" which results from the war in Ukraine (and missing or failed long term strategies in politics earlier) . But calculations show that this would kill our forests fast, because of over consumption, again. And, last but not least, studies show that wood stoves produce "second hand smoke 2.0" which isn't healthy either. So just changing fuels from dead dinosaurs to dead trees won't help us in the long range, I expect.
- enegg 4y ago
- patrickyeon 4y agoIf anyone is interested in the full text, there's a PDF copy linked from some of the co-authors' research group here https://www.romangroup.mit.edu/publications https://www.romangroup.mit.edu/publications
- credit_guy 4y agoThis is great. Right now all gasoline sold in the US needs to contain 10% bioethanol. That's just a handout scheme to corn farmers, who plant this corn on 30 million acres of good agricultural land. One out of three acres planted with corn is used for bioethanol. If we convert this area to produce, let's say, bamboo, which could be converted to bio jet fuel, then that would make much more sense. Surface traffic can and will be electrified in the years to come. Air traffic will never get electrified. We need a carbon neutral source for jet fuel.