GRA
Well-known member
Via GCC: http://www.greencarcongress.com/2016/03/20160312-ual.html
United Airlines begins commercial-scale use of renewable jet fuel; 15M gallons over 3-year period
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RegGuheert
Well-known member
There's nothing "sustainable" about biofuels. At EROEI values near unity, you consume just as much petroleum to produce the biofuel as you would simply flying on it directly. But you do significantly more damage to the environment by building all the equipment and infrastructure and farming the land than if you simply used the petroleum fuel. It's nothing more than a government handout to agribusiness.GRA said:
The world would be much better off without this type of "environmentalism."
As we have discussed elsewhere, an acre of PV in the desert can propel a fleet of BEVs a total of 1,000,000 miles per year while an acre of Iowa farmland can only propel ONE oil-burner about 10,000 miles per year. In other words, the land footprint is about 1/100 when using PV and BEVs. And EROEI is significantly better.
Since aviation is an area where extremely-advanced technologies are frequently afforded to enhance performance, perhaps this is an area where hydrogen should be investigated. Are there any projects out there to convert turbofans to run on hydrogen rather than liquid fuels? It seems there was recently some "green washing" at Ryan Air about replacing their APUs with fuel cells. It seems an earnest effort in that direction might be more worthwhile long term.
ETA: FWIW, here is an article from the BBC discussing why hydrogen is losing out in aviation to biofuels:
Aparently there is a new type of biofuel called "unobtainium." :roll:
GRA
Well-known member
As has been discussed previously at length, sustainable biofuels require EROEI above unity, as well as no use of croplands that can be used for fuel - in other words, no corn etc. The article you cite is rather old (2010), but I don't disagree with the basic premise that H2generally isn't the way to go for aviation. Development of cellulosic and algal-based biofuels stalled for a while, but progress has picked up considerably in the past few years, and we're now seeing commercial-scale cellulosic plants. Whether this particular supplier meets the definition of sustainable I couldn't say, but I'm sure that the one area where liquid drop-in biofuels will be essential is medium and long-haul aviation, as no other fuel has the energy and power density required. Whether fuel cells or some other tech will work for short hoppers remains to be seen. The next transportation biofuel requirement would be ships, and DoD is already onto that: http://greenfleet.dodlive.mil/energy/great-green-fleet/RegGuheert said:
Heres'a another article: http://www.eesi.org/articles/view/u.s.-navy-deploys-great-green-fleet-in-bid-to-reduce-military-energy-use
DoD has realized for some time that eventually the fossil fuels will run out, and that in any war restrictions on its availability as well as price volatility could be critical, so they've been subsidizing research for years if not decades on the development of drop-in biofuels for both aviation and ships. It's just now starting to come to fruition. See http://greenfleet.dodlive.mil/energy/task-force-energy/
RegGuheert
Well-known member
Yes, I have posted on this topic extensively and, no, getting above unity EROEI is NOT sufficient to make biofuels sustainable. Getting above an EROEI of 1:1 ONLY allows us to reduce the amount of fossil fuels consumed for the ongoing production of biofuels. In order to make biofuels sustainable, you not only need to pay back the energy used to make the biofuels, but you also need to pay back all of the energy used to build all of the infrastructure needed to create the biofuels: tractors, biofuel processing plants, etc. That gets the minimum EROEI up to around 3:1. But at 3:1 EROEI, you find that you do not have sufficient energy left over to grow the industry at a non-zero rate. As a result, the energy needed to grow the industry comes from non-sustainable resources.. To do that, you need to get EROEI much higher, like above 10.GRA said:
Are there biofuels out there with an EROEI above 10? Frankly, I don't think that is even on the horizon.
And then you have the massive land-use issues. No, algal-based biofuels do not address this issue since they produce such minute amounts of biofuel.
As I said, biofuels solve no problems. They only add to existing ones. Burning biofuels in cars is hurting our environment. Burning it in airplanes will hurt our environment even more.
That brings us back to PV. EROEI is currently above 10 (by how much is the only matter of debate). Land use required for PV for transportation is minuscule when compared with biofuels, as noted. And that goes down as efficiency improves. 20% sunlight-electricity conversion efficiency is likely far beyond anything biofuels could ever hope to achieve.
So, how do you fly airplanes on PV?
- Batteries? This is the most efficient approach, but batteries do not get lighter as they discharge, so they have a distinct disadvantage for long-haul flight. I expect battery-powered flight to address short range needs in the future, but I have trouble envisioning it for long-range flight or cargo. This is similar to my views of BEVs for land transportation.
- Flow batteries? Possibly, but these also do not get lighter as the flight progresses. I'm not sure what the energy cost is, either.
- Hydrogen? In liquid form, hydrogen contains 3X the energy of hydrocarbon fuels by weight. Unfortunately, it takes up 4X the volume. Also, liquid hydrogen is extremely unlikely to stay liquid in a crash, which likely will cause some pretty spectacular fireballs when liquid-hydrogen-fueled airplanes crash. On top of all that, production of hydrogen will immediately cut the EROEI of PV by over half. Perhaps to less than 1/3. So the question is whether or not there is a way to store sufficient hydrogen in a safe, lightweight container for flight. Metal hydrides are not light and are energy-intensive.
- Some other liquid fuel? This may end up being the ultimate solution. But most liquid fuels require significant energy to manufacture. This will improve as technology advances, but who knows how long it will take?
GRA
Well-known member
I don't disagree with any of this, I was trying to keep my reply reasonably short, without including all the past discussion points.RegGuheert said:
They did, but they are approaching commercial quantities now, and R&D has (naturally) been aimed at continuing to increase yields. AFAIK we don't have a dedicated biofuel thread, and I don't post lab results on any alternative fuel/storage except at long intervals to show the current state and direction of research, while noting that commercialization is never guaranteed. I think it's time to have a dedicated thread, as I consider that they may be one of the pathways that will be needed to move us off fossil fuels, so I'll start one if there isn't an existing one.RegGuheert said:
