# Zero (not NET) carbon emissions aircraft with minimum changes to current engines **URL:** \ **Category:** In My Humble Opinion\ **Created:** [August 18, 2021, 3:20pm UTC](https://boards.straightdope.com/t/zero-not-net-carbon-emissions-aircraft-with-minimum-changes-to-current-engines/949099 "2021-08-18T15:20:31Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\ **Post date:** [August 18, 2021, 3:20pm UTC](https://boards.straightdope.com/t/zero-not-net-carbon-emissions-aircraft-with-minimum-changes-to-current-engines/949099/1 "2021-08-18T15:20:31Z")
Inspired by the battery powered aviation thread : [https://boards.straightdope.com/t/fuel-economics-of-battery-powered-airplanes/](https://boards.straightdope.com/t/fuel-economics-of-battery-powered-airplanes/) What do the aviation experts on the board think about ammonia powered jet engines ? And the claims presented here (it seems Rolls Royce has a collaboration with them) : > **[Reaction Engines - Making Beyond Possible](https://reactionengines.co.uk)** > > We're innovating in pursuit of the world's net zero goals. Transforming high-speed flight, and pioneering space access and sustainable technologies to elevate life on Earth. It also looks like Raytheon is working on it : [https://www.rtx.com/News/2020/12/09/ammonia-could-fuel-the-future-of-sustainable-flight](https://www.rtx.com/News/2020/12/09/ammonia-could-fuel-the-future-of-sustainable-flight) ---
**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\ **Post date:** [August 18, 2021, 3:43pm UTC](https://boards.straightdope.com/t/zero-not-net-carbon-emissions-aircraft-with-minimum-changes-to-current-engines/949099/2 "2021-08-18T15:43:40Z")
Wouldn’t biofuels be zero **net** emissions, and a lot easier? ---
**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\ **Post date:** [August 18, 2021, 3:45pm UTC](https://boards.straightdope.com/t/zero-not-net-carbon-emissions-aircraft-with-minimum-changes-to-current-engines/949099/3 "2021-08-18T15:45:33Z")
Maybe we can discuss biofuels in a separate thread ? I was hoping to get some answers on Ammonia. ---
**Author:** ![gnoitall](https://avatars.discourse-cdn.com/v4/letter/g/bb73d2/32.png) [@gnoitall](https://boards.straightdope.com/u/gnoitall)\ **Post date:** [August 18, 2021, 4:30pm UTC](https://boards.straightdope.com/t/zero-not-net-carbon-emissions-aircraft-with-minimum-changes-to-current-engines/949099/4 "2021-08-18T16:30:07Z")
Well, your title doesn’t indicate that. If you want the discussion to be that narrow, you may consider asking a moderator to tweak the title. ---
**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\ **Post date:** [August 18, 2021, 5:06pm UTC](https://boards.straightdope.com/t/zero-not-net-carbon-emissions-aircraft-with-minimum-changes-to-current-engines/949099/5 "2021-08-18T17:06:54Z")
The title says " Zero carbon emissions aircraft with minimum changes to current engines" - It doesn’t say **NET** Zero carbon emissions aircraft The links provided in the OP are also NOT for **NET** Zero carbon emissions aircraft Mods - please change the title to **Zero (not NET) carbon emissions aircraft with minimum changes to current engines** ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [August 18, 2021, 6:03pm UTC](https://boards.straightdope.com/t/zero-not-net-carbon-emissions-aircraft-with-minimum-changes-to-current-engines/949099/6 "2021-08-18T18:03:52Z")
> [@am77494](#): > > Mods - please change the title to **Zero (not NET) carbon emissions aircraft with minimum changes to current engines** You can’t ask the mods to do something just by adding a post. Mods don’t read every post on the entire board. Flag your OP post (three dots to show “More” then Flag) and request the title change. ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [August 18, 2021, 6:18pm UTC](https://boards.straightdope.com/t/zero-not-net-carbon-emissions-aircraft-with-minimum-changes-to-current-engines/949099/7 "2021-08-18T18:18:59Z")
Note that hydrogen can be used as jet fuel and meets your zero-emissions criterion; in fact the Airbus ZEROe project is investigating exactly that. As early as 1988, the Soviet Tu-155 tri-jet was experimentally powered with hydrogen. If you just want to discuss ammonia, you should say so. [https://www.airbus.com/innovation/zero-emission/hydrogen/zeroe.html](https://www.airbus.com/innovation/zero-emission/hydrogen/zeroe.html) ---
**Author:** ![md-2000](https://avatars.discourse-cdn.com/v4/letter/m/9d8465/32.png) [@md-2000](https://boards.straightdope.com/u/md-2000)\ **Post date:** [August 18, 2021, 6:47pm UTC](https://boards.straightdope.com/t/zero-not-net-carbon-emissions-aircraft-with-minimum-changes-to-current-engines/949099/8 "2021-08-18T18:47:49Z")
Wouldn’t ammonia result in nitrogen byproducts? Diesel cars emit nitrous oxides (NO and NO2) due to the heat and compression of the combustion cycle. I have trouble imagining the turbojet being cleaner. the issue I assume (IANAChemist) is whether the “cracking” process truly separates _all_ the ammonia into hydrogen and nitrogen, or whether some goes through the engine as ammonia? Nitrous oxides present their own interesting environmental/medical problems, especially if this implies the area around airports will be high concentrations. [https://www.transportenvironment.org/sites/te/files/publications/2015\_09\_Five\_facts\_about\_diesel\_FINAL.pdf](https://www.transportenvironment.org/sites/te/files/publications/2015_09_Five_facts_about_diesel_FINAL.pdf) However, given the difficulties of storing hydrogen in bulk, this may be a passable compromise. But ammonia evaporates at -33C (-28F) so presumably the tanks would hold the fuel under a decent pressure. Were most jet liners built to hold appreciably pressurized fuel? Also consider that whether hydrogen or ammonia, having the aircraft sit in a take-off waiting queue for an hour or more in the hot sun with a super-cooled fuel while fully fueled may be more problematic that with ordinary jet fuel. Even venting pressure with ammonia may create a hazardous environment. (None of this makes it impossible to use - just that any fuel comes with its own problems.) ---
**Author:** ![zimaane](https://avatars.discourse-cdn.com/v4/letter/z/a3d4f5/32.png) [@zimaane](https://boards.straightdope.com/u/zimaane)\ **Post date:** [August 18, 2021, 7:11pm UTC](https://boards.straightdope.com/t/zero-not-net-carbon-emissions-aircraft-with-minimum-changes-to-current-engines/949099/9 "2021-08-18T19:11:44Z")
The energy density of ammonia is about half that of conventional jet fuel, so an ammonia powered plane will have much less range than an equivalent plane powered with aviation fuel. Not a complete deal breaker, but definitely an issue. ---
**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\ **Post date:** [August 18, 2021, 7:12pm UTC](https://boards.straightdope.com/t/zero-not-net-carbon-emissions-aircraft-with-minimum-changes-to-current-engines/949099/10 "2021-08-18T19:12:17Z")
> [@CookingWithGas](#): > > Flag your OP post (three dots to show “More” then Flag) and request the title change. Thanks for the directions and done. > [@wolfpup](#): > > Note that hydrogen can be used as jet fuel and meets your zero-emissions criterion; in fact the Airbus ZEROe project is investigating exactly that. Thats what this post is about, Ammonia is just the carrier of hydrogen - because it is easy to liquefy ammonia and it has no carbon. Hydrogen is easily obtained from ammonia through a catalytic process : Pasting from the link provided in the OP > **[Reaction Engines - Making Beyond Possible](https://reactionengines.co.uk)** > > We're innovating in pursuit of the world's net zero goals. Transforming high-speed flight, and pioneering space access and sustainable technologies to elevate life on Earth. ---
**Author:** ![Grey](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Grey](https://boards.straightdope.com/u/Grey)\ **Post date:** [August 18, 2021, 7:27pm UTC](https://boards.straightdope.com/t/zero-not-net-carbon-emissions-aircraft-with-minimum-changes-to-current-engines/949099/11 "2021-08-18T19:27:55Z")
Doesn’t the process to create NH[sub]3[/sub] rely heavily on natural gas? ---
**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\ **Post date:** [August 18, 2021, 7:28pm UTC](https://boards.straightdope.com/t/zero-not-net-carbon-emissions-aircraft-with-minimum-changes-to-current-engines/949099/12 "2021-08-18T19:28:50Z")
> [@md-2000](#): > > Also consider that whether hydrogen or ammonia, having the aircraft sit in a take-off waiting queue for an hour or more in the hot sun with a super-cooled fuel while fully fueled may be more problematic that with ordinary jet fuel. Tanks of Ammonia are commonly shipped on roads as fertilizer - in fact many farmers have ammonia tanks on their farm. Terminals keep ammonia at -28F 15psi, while the transport / farmer tanks are at 265psi at ambient temperature (like propane). Ammonia is hazardous though, and needs a lot of safe handling. ---
**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\ **Post date:** [August 18, 2021, 7:30pm UTC](https://boards.straightdope.com/t/zero-not-net-carbon-emissions-aircraft-with-minimum-changes-to-current-engines/949099/13 "2021-08-18T19:30:21Z")
> [@Grey](#): > > Doesn’t the process to create NH[sub]3[/sub] rely heavily on natural gas? Yes - you can make it from Hydrogen, which is in turn derived from natural gas. You can also make it from Hydrogen, which is in turn derived from electrolyzing water. The power for electrolysis comes from wind / solar. There is no hydrocarbons involved ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [August 18, 2021, 7:38pm UTC](https://boards.straightdope.com/t/zero-not-net-carbon-emissions-aircraft-with-minimum-changes-to-current-engines/949099/14 "2021-08-18T19:38:32Z")
> [@am77494](#): > > > [@wolfpup](#): > > > > Note that hydrogen can be used as jet fuel and meets your zero-emissions criterion; in fact the Airbus ZEROe project is investigating exactly that. > > Thats what this post is about, Ammonia is just the carrier of hydrogen - because it is easy to liquefy ammonia and it has no carbon. Hydrogen is easily obtained from ammonia through a catalytic process : OK, but it’s quite a stretch to suggest that liquid (L) H2 and (L)NH3 imply the same technology. All three of the ZEROe initiatives are solely based on aircraft carrying liquid hydrogen, which has technical challenges but has three times the energy density by mass of Jet A-1, and well over six times the energy density of (L)NH3. The whole infrastructure inside and outside the aircraft is completely different. ---
**Author:** ![Sam\_Stone](https://avatars.discourse-cdn.com/v4/letter/s/ecccb3/32.png) [@Sam\_Stone](https://boards.straightdope.com/u/Sam_Stone)\ **Post date:** [August 19, 2021, 7:51pm UTC](https://boards.straightdope.com/t/zero-not-net-carbon-emissions-aircraft-with-minimum-changes-to-current-engines/949099/15 "2021-08-19T19:51:00Z")
A potential showstopper is accident safety and leak safety. A thousand gallons of released ammonia is a seriots hazard. And everyone who works on the fuel system and infrastructure would be dealing with some pretty hazardous stuff. ---
**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\ **Post date:** [August 19, 2021, 7:57pm UTC](https://boards.straightdope.com/t/zero-not-net-carbon-emissions-aircraft-with-minimum-changes-to-current-engines/949099/16 "2021-08-19T19:57:49Z")
> [@Sam\_Stone](#): > > A potential showstopper is accident safety and leak safety. Agreed. However, it is routine in the United States for farmers to have Ammonia Nurse Tanks. Ammonia Nurse Tanks are usually 1000 gal or 1500 gal and the regulations are fairly mature around them Like this [https://www.michigan.gov/documents/msp/Fries\_350309\_7.pdf](https://www.michigan.gov/documents/msp/Fries_350309_7.pdf) or [Nurse Tank Anatomy | Minnesota Department of Agriculture](https://www.mda.state.mn.us/nurse-tank-anatomy)