Burning Buried Sunshine (2003)
lovecg 2021-08-17 20:52:14 +0000 UTC [ - ]
A better intuition is this: plants, etc. used energy to create two products, oxygen (which went into the atmosphere) and hydrocarbons (buried in the ground). When we recombine them and add heat, we reconfigure some bonds and release energy in the oxygen bond. The hydrocarbons act as a “sponge” for the oxygen atoms, and the denser the sponge the more energy we can release.
If it was the oxygen buried underground we would probably call it “fuel”!
Robotbeat 2021-08-17 22:15:11 +0000 UTC [ - ]
I read a proposal to send an aircraft to Titan and bring along oxygen as the energy source to burn with the methane in the atmosphere. (It works… sort of. In a methane and oxygen stoichiometric reaction, the oxygen is 4/5ths the mass so it’s not nearly as good of a deal as it is on Earth.)
blendergeek 2021-08-18 02:09:56 +0000 UTC [ - ]
It truly doesn't matter which one you consider it to be, given that both are technically incorrect.
> The energy is in them being split apart.
This is a common misconception (likely) perpetuated by highschool chemistry textbooks. The energy is actually release by the combination of oxygen with hydrogen and carbon. Let me explain.
It takes energy to break chemical bonds. Some bonds take more energy to break, others take less. When a bond is created, an amount of energey (roughly) equal to the energy require to create the bond is released.
Here I will demonstrate the combustion of a simple hydrocarbon:
CH4 + 2 O2 -> CO2 + 2 H2O
When this reaction takes place, there is not energy "stored" in either the Carbon-Hydrogen bonds or the Oxygen-Oxygen bonds that is "given off". Rather, energy is actually required to break the bonds. It goes something like this:
CH4 + 2 O2 + (a little bit of energy) -> CO2 + 2 H2O + (a lot of energy).
Making hydrocarbons (or hydrogen from water) is an energy intensive process because breaking the bonds in CO2 and H2O requires a lot of energy.
lovecg 2021-08-18 03:47:53 +0000 UTC [ - ]
The products on the right side sit at a lower energy level (they hold together “tighter”) overall. On the left, O2 needs less energy to break up while CH4 needs more, so in that sense the energy “comes” from O2 being easier to break apart. Conceptually I imagine these as a bunch of magnets with the two “magnets” in O2 held at a larger gap (so easier to take apart). With a jolt, things reconfigure and snap into a tighter pattern, and there’s an overall energy release.
Robotbeat 2021-08-18 03:39:07 +0000 UTC [ - ]
mr_toad 2021-08-18 01:25:00 +0000 UTC [ - ]
aidenn0 2021-08-17 23:04:55 +0000 UTC [ - ]
Surely plants are majority water by mass? A quick google claims 89-90% water[1]
1: https://www.toppr.com/ask/question/the-percentage-of-water-i...
wrytour 2021-08-18 01:00:32 +0000 UTC [ - ]
aidenn0 2021-08-18 02:39:20 +0000 UTC [ - ]
User23 2021-08-18 00:10:03 +0000 UTC [ - ]
criticaltinker 2021-08-17 21:10:55 +0000 UTC [ - ]
Wow, and this is a lower bound because it doesn't even consider manufacturing and distribution.
My cognitive dissonance at the gas station is approaching an all-time high.
dredmorbius 2021-08-18 05:34:55 +0000 UTC [ - ]
https://www-legacy.dge.carnegiescience.edu/DGE/Dukes/Dukes_C...
I'd stumbled across this through my own research, trying to find literature with a detailed description of fossil-fuel formation. I've since found it referenced by numerous other works --- yes, one of my forms of entertainment is looking for familiar citations amongst footnotes. Smil's Energy and Civilization being one work citing Dukes.
It's not just the material conversion that's staggering, there's the time of accumulation. For petroleum, humans burn in one year a quantity which took five million years to accumulate.
version_five 2021-08-17 22:09:35 +0000 UTC [ - ]
Robotbeat 2021-08-17 22:12:30 +0000 UTC [ - ]
throwaway09223 2021-08-18 01:09:48 +0000 UTC [ - ]
Soybeans are a common way of capturing carbon from the atmosphere, using solar energy, to produce diesel.
_3u10 2021-08-17 22:54:13 +0000 UTC [ - ]
yetihehe 2021-08-18 06:59:19 +0000 UTC [ - ]
_3u10 2021-08-19 08:44:02 +0000 UTC [ - ]
I meant freshwater cycle time.
Yes there are certainly places that run out of water, I meant more places like Vancouver where the city just doesn’t build a bigger reservoir and instead bemoans an annual water shortage.
pvaldes 2021-08-18 09:35:10 +0000 UTC [ - ]
The correct number would be closer to 3.54 tonnes of plant material. The other 18.91 tonnes aren't spent. They are instead fully recycled and re-enter in the system (or go away out of the oil processing chain).