Isn't synthetic fuel much more promising?
Another approach is to pull the CO2 straight out of sea water. Apparently the US Navy thinks this might be a viable approach, since their nuclear aircraft carriers have power to spare.
The general idea is to use electrolysis to produce hydrogen, then combine that with atmospheric CO2 to produce methanol.
For instance: https://www.efuel-alliance.eu/efuels/what-are-efuels
On the Costs & Outlook page of this site, they list their potential feedstocks; it's all biomass, except for the 'Technical Potential "Unlimited"' column, which mentions Power-to-Liquids. But how does that actually work and does it actually make sense?
Related parody of carbon capture: https://www.youtube.com/watch?v=MSZgoFyuHC8
The U.S. navy is interested in a fuel synthesizer that works on co2, seawater and uranium and they can pay more than you per gallon because you don’t have to refuel an aircraft carrier in a war zone.
Energetically, the principal synthetic fuels will be anhydrous ammonia and hydrogen. Capturing CO2 to make methane and kerosene is possible but more expensive. In particular, you need hydrogen as input, and must both capture and crack the CO2.
But for some uses you still need hydrocarbons, at least for now. Given carbon taxes subsidizing synthetics, the synthetics could be competitive.
In the longer term, aviation does much better with liquid hydrogen fuel, but it takes new airframes or, at least, extensive retrofits.
> A problem with biofuel is scaling it up, see: https://ieeexplore.ieee.org/document/7498153. According to that article the U.S. would need to devote "an area bigger than Texas and California and Pennsylvania combined" to crops specifically for its own jet biofuel needs. That's just for flying, not for food or fuel for ground transportation or anything else.
Also that article says that from 2009-2013 a $100 million effort was made to figure out how to get sufficient synthetic fuel from algae but they eventually gave up and went back to the drawing board.
The future has no place for biofuel in any substantial amount.
Firewood and derivatives have always had an important place in heating and cooking, and are likely to continue in that role for a while. Other types of biomass based hard fuels (from recycled garbage/waste, algae, etc) will most likely also play a role in electricity production and heating, but perhaps a small one (unless algae based biomass takes off).
And for liquid fuels for transportation use, algae may also end up being a competitor to hydrogen when oil runs out. I remember there were a lot of companies working in that space 10 years ago, but then there was the oil price crash in 2015, and it seems many switched away.
For instance algenol was positioning itself as a fuel company, but appear to have diversified:
https://www.algenol.com/sustainable-products/?category=ndust...
If oil prices remain at current levels, though, algae may be only a few years away from scaling up to take a significant part of the market.
Growing algae occupies >10x the area of floating solar panels producing the same usable energy. Harvesting and processing algae costs >>1 orders of magnitude more than delivering electrical power via wire.
The reasonable expectation is that transitions will be toward cheaper alternatives, with societal inertia acting to delay transition well beyond the point of obvious benefit. Thus, existing nukes will continue operating well after building solar + storage and then switching to that would be cheaper.
https://www.nve.no/Media/7326/energibruk_energivar_2014-kopi...
Here is similar data from Sweden:
https://www.researchgate.net/profile/Egnell-Gustaf/publicati...
Here is for the world, my understanding is that "Traditional Biomass" is mostly firewood there too:
https://ourworldindata.org/exports/global-energy-substitutio...
Does the lady of the house want to collect scraps of firewood and then cook in a hot already smokey kitchen or on a only heats the pan induction cooktop? Yeah.
Getting together $10 for a stove that needs 5x less firewood is a challenge. They need a new one every year because making one that lasts costs more.
It's capturing energy in point A and being used at point B. You can't just look at point B and yell "CO2 emissions!".
That seems to be the big if.
For pure e-fuels they project 32 PWh. That is, to put it in perspective, more than the total world electricity production today. You'll want to use every technology available to do this in a more efficient way - batteries for very short ranges, hydrogen for mid ranges, e-fuels only for long range where nothing else works. It'll still be very challenging and likely the current growth projections of the aviation industry will be seen as unrealistic fantasies at some point in the future.
Total annual electricity production is 161 PWh. THe PDF you linked puts it in perspective by saying that if it were purely powered by renewable energy it would increase the size of the renewable energy sector by 3 to 5 times. In other words this doesn't sound hard at all from an electricity standpoint. If electrical generation were half the cost it would be economical right now.
> We find that an electricity emissions factor of less than 139 g CO2e per kW h is required for this [Direct Air Capture system paired with Fischer–Tropsch synthesis] pathway to provide a climate benefit over conventional diesel fuel.
The grid averages in most regions are higher than that. I don't think multiplying current renewable generation just for jet fuel is easy.
Basically, overprovision and then set electricity rates based on demand, and the renewable energy "storage problem" might just sort itself out. Of course, all those windmills and solar panels will cost an awful lot, so it might not be as simple as "overprovisioning".
Overprovisioning solar to power the grid on ice cold, windless new moon night is going to be hard. Having somewhere to put excess energy and some overprovisioning is always good, but it won't solve all storage problems.
I'd be really happy if there were a good way for me to turn excess electricity into something I could use later. Maybe that's hydrogen. Maybe that's capturing carbon and putting it into liquid fuels. Maybe that's creating graphite that I can use for fun personal projects.
But regardless, I don't expect grid electricity prices to fall. Probably not in the US. Definitely not in CA.
Did I mention that they are bad for the ozone layer?