According to an article I read, the total lifecycle greenhouse emissions is 10% of fossil jet fuel.
Here’s how it works: A farmer grows crops like, say, beans, which really energy from the sun and carbon from the air, and use it to make tasty sugars and proteins. You eat the beans, and your body absorbs the easy nutrients to get. But the stuff that’s hard to get out is left in the food mass and turned into poo. You go to the toilet and your waste is collected by the sewage system. Then this company takes your poo, and uses energy from the grid to subject it to a process that makes crude oil. Then they distill jet fuel from the crude.
All of the carbon that is in the jet fuel came from those beans you ate, which got it from the air. So the jet fuel isn’t adding any new carbon to the air. There are still emissions associated with putting energy into the poo to refine it into oil, though, because it’s using energy from the grid.
ForgotAboutDre@lemmy.world 10 months ago
Yes. But the waste is likely to still produce methane that has a bigger climate warming effect that the equivalent co2 of burned but for a shorter period. The general consensus suggests it’s better to burn methane than release it into the environment.
The better solution is to fly less, or wait till flying truly green. The big issue is the incredible amount of subsidy we allow for airlines. Tax or fuel for aircraft is very low. If we cut these subsidies and starting taxing aircraft fuel at similar rates to cars electric/hydrogen aircraft would come about much sooner.
Numberone@startrek.website 10 months ago
Also, if its in human poo it’s already in the carbon cycle and so really less of an issue. The problem is bringing up carbon that’s been removed from the cycle (subterranean oil or gas pockets) and putting that back into circulation. Granted it would be better to pull carbon out of the atmosphere (somehow), but at least using poo wouldn’t be adding NEW carbon. That’s my understanding anyway.
exocrinous@lemm.ee 10 months ago
Carbon can exist in the atmosphere as carbon dioxide (CO2), methane, (CH4), or as a lot of bigger organic molecules like ethane. Over years, methane you release will eventually decay into CO2. But until that happens, the methane has 20 times the greenhouse effect that CO2 does. So processes like this can take CO2 from the air and turn it into methane, which is bad.
We need less flying, but if we’re going to have flying, it should use technologies like this which have 1/10th the lifecycle emissions of fossil jet fuel.