Coconut Oil Jet Fuel Matches Kerosene's Efficiency in Engine Tests
Researchers at Osaka Metropolitan University have developed a low-energy method to produce jet fuel from discarded coconut oil, and their engine tests show it performs nearly as efficiently as conventional kerosene. Blending up to 50% biofuel with kerosene maintained thermal efficiency and thrust, while cutting unburned hydrocarbon emissions by up to 40%. However, the blends burned more fuel and emitted slightly more carbon monoxide, and the fuel's oxygen content currently falls outside aviation standards.
Coconut oil-derived biofuel is not a ready swap for conventional jet fuel yet, but the performance data from this study makes a real argument that the concept is worth pursuing.
- landl0rd
This isn't proper SAF, it's basically C8/10 biodiesel. No aromatics which is one of the perennial problems with SAF, due not just to volumetric energy density but nitrile seals not swelling enough. Integral wing tank seals usually expect aromatic exposure also. This is why some of the catalytic routes/CHJ are of greater interest, cycloparaffins/napthenes recover some of this vs a more biodiesel-ish blend, but even 50% cycloparaffin doesn't fully recover swell. These are solvable backwards compatibility issues but not in the short or medium term.
More egregiously FAME is a polar solvent that eats your elastomers, even some fluoroelastomers. It will also attack your polysulfide tank sealant. The remark that it's "technically feasible" to decrease oxygen through hydrogenation is not at all sufficient. Now you're into requiring catalyst beds and a hydrogen plant which makes this much less appealing. Plus ester instability when you sink heat into fuel. Plus freeze point. This is literally a tracked contaminant banned above mg/kg levels that doesn't even have very good properties otherwise they want to run as a major constituent of fuels.
- clickety_clack
Do coconuts grow particularly efficiently?
Edit: The US created biofuel subsidies a few years ago and it’s led to poor use of land with questionable climate impact. It’s effectively become a wealth transfer to support poor rural American communities, which isn’t necessarily a bad thing but there’re probably more effective ways to do that intentionally.
- JoeAltmaier
50 MTons of coconut oil are produced per year (approximately). Is this a significant amount, compared to oil derived from crude (where gas currently comes from).
- andy_ppp
How many coconuts do we need to support current aviation needs? I’m guessing it’s not likely this will work economically?
- pfdietz
You want a fuel that's chemically identical to current jet fuel, not one burdened with extra oxygen. Yes, this would require more energy, but it would be used more effectively in jets.
A drop-in compatible jet fuel can be made by hydrodeoxygenation of biomass, using Virent's process. The waste cellulose in current US waste streams would be more than enough to displace all current US jet fuel consumption. An extra source of hydrogen would be needed to do this, but hydrogen can be made renewably (and, indeed, that's a good way to provide dispatchable demand to help deal with renewable intermittency, and will have to be done anyway to displace the use of natural gas to make hydrogen.)
- splittydev
If it burns more fuel, how is it "about as efficient"? That doesn't seem to make much sense to me.
> New research found that aviation biofuel made from coconut oil can power a small jet engine about as efficiently as traditional jet fuel, with lower unburned hydrocarbon emissions, though the blends burn more fuel and emit slightly more carbon monoxide.
- dofm
So we can't have the dark chocolate Bounty bar anymore but we can use coconuts to fuel planes?
This isn't the future I want.
- wronex
I think this is awesome. Anything we can do to get away from burning fossil fuel is a win in my book. I don’t know about this particular effort, but it seems to me that aviation could really need some big wins in this direction. Last I looked we still run smaller planes on leaded fuel. Crazy.