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When electricity from solar and wind power were much more expensive, biomass looked attractive as a lower cost (if limited-availability) energy source. I'd say

When electricity from solar and wind power were much more expensive, biomass looked attractive as a lower cost (if limited-availability) energy source. I'd say that it is still potentially attractive for making liquid fuels, but less because of its embodied energy content and more as a compact source of carbon that has recently been removed from the atmosphere. Cellulosic ethanol is pretty terrible even when the process is operating as planned: http://www.ethanolproducer.com/articles/15344/zero-to-10-million-in-5-years http://www.ethanolproducer.com/articles/15344/zero-to-10-mil... 70 gallons of ethanol from 1 short ton of cellulose means 230 kg from 1000 kg of cellulose. There's 444 kg of carbon in that much cellulose, enough to make 518 kg of diesel fuel if given enough externally supplied hydrogen. The energy content of the final fuel from 1 tonne of cellulose is 23.6 GJ for diesel and only 6.9 GJ for the ethanol. Liquid biofuels from non-cellulosic inputs have even worse areal productivity. (Barring (theoretically) algae, which nobody seems to be able to implement at industrial scale.) US airline fuel consumption peaked in 2007 at 20 billion gallons per year: https://www.eia.gov/todayinenergy/detail.php?id=31512 https://www.eia.gov/todayinenergy/detail.php?id=31512 That's about 63 million tonnes of kerosene/diesel. You'd need at least 122 million tonnes of cellulosic biomass to supply carbon for that much fuel. You'd also need refiners, crackers, and recapture in addition to F-T units to ensure that both too-light and too-heavy carbon compounds get recycled to produce liquid hydrocarbons of the desired saturation and molecular weight. It would basically be running a state of the art petrochemical complex with biomass gasifiers and electrolytic hydrogen bolted on. But assuming you did all that, the raw material availability looks relatively favorable. As of 2005, this report estimated that over 300 million tonnes of currently-unused dry biomass could be sustainably harvested from forests and agricultural wastes: https://www1.eere.energy.gov/bioenergy/pdfs/final_billionton_vision_report2.pdf https://www1.eere.energy.gov/bioenergy/pdfs/final_billionton...

dredmorbius 7y ago
I can confirm pretty much all of that from my own research, with most of those topics / technologies at least touched on at https://old.reddit.com/r/dredmorbius https://old.reddit.com/r/dredmorbius The fact of peak US aviation fuel surprised the heck out of me when I stumbled across it. I'm holding out hopes for wind/solar feeding F-T for at least some liquid fuels production.
dredmorbius 7y ago
The reduction in fuel consumption apparently also suprised the FAA. In its 2002 RITA projection, the forecast total commercial aviation consumption for 2012 (that's nearly 8 years ago now) was ~33 billion gallons. As of 2016, it was still only aroun 17 billion, or nearly 50% below the forecast for four years prior. Whether this is a testiment to efficiency or a harbinger of peak oil, I'm not entirely certain. Though as an example of the shifts in resource utilisation following prices, it's instructive. The efficiency improvements, it should be noted, are in both per revenue passenger mile and per capacity passenger mile. Those result both from an increased number of seats per aircraft (that's where your legroom's gone), and in the number of paying butts in those seats, largely courtesy improved predictive sales / incentives methodologies. And improvements in aircraft efficiencies. Such as by high-bypass turbofan engines, which require ever higher, and forward-positioned, mounting systems. Which then affect aircraft handling and stability.... There are probably limits to both approaches.

dredmorbius 7y ago

I can confirm pretty much all of that from my own research, with most of those topics / technologies at least touched on at https://old.reddit.com/r/dredmorbius https://old.reddit.com/r/dredmorbius The fact of peak US aviation fuel surprised the heck out of me when I stumbled across it. I'm holding out hopes for wind/solar feeding F-T for at least some liquid fuels production.

dredmorbius 7y ago

The reduction in fuel consumption apparently also suprised the FAA. In its 2002 RITA projection, the forecast total commercial aviation consumption for 2012 (that's nearly 8 years ago now) was ~33 billion gallons. As of 2016, it was still only aroun 17 billion, or nearly 50% below the forecast for four years prior. Whether this is a testiment to efficiency or a harbinger of peak oil, I'm not entirely certain. Though as an example of the shifts in resource utilisation following prices, it's instructive. The efficiency improvements, it should be noted, are in both per revenue passenger mile and per capacity passenger mile. Those result both from an increased number of seats per aircraft (that's where your legroom's gone), and in the number of paying butts in those seats, largely courtesy improved predictive sales / incentives methodologies. And improvements in aircraft efficiencies. Such as by high-bypass turbofan engines, which require ever higher, and forward-positioned, mounting systems. Which then affect aircraft handling and stability.... There are probably limits to both approaches.