High Flying

Can you make ultra-performing diesel and jet fuels from essential oils found in cannabis sativa, a/k/a marijuana?

Turns out, you can.

Caryophyllene is a highly fragrant molecule found in a whole bunch of plants, and is the third-highest active component in catnip.

It’s found in oregano, pepper, hops, cinnamon, basil, black caraway, and in pretty good concentration in oil of cloves. You probably get the idea right away that it is widely distributed and smells pretty good.

A concentrated source of it is from oil prepared from cannabis sativa, which in the versions that are cultivated to feature high concentrations of the psychoactive molecule tetrahydrocannabinol (THC), is known as marijuana.  Or dope, weed, bud, My Good Friend Smoky, magic salad, or any of a hundred other names.

Another varietal of Cannabis sativa, is known as hemp which for many years, you may recall, was a trusted source for industrial fiber, rope, and cloth — before its cultivation fell afoul of the anti-marijuana laws. (Note: Hemp is defined in the US as being 0.3%THC or less of dry weight (field sample) thus low THC types of Cannabis. So saying hemp is aka marijuana is incorrect. Hemp is part of the Cannabis sativa L. plant family but it is not of the psychoactive types (common name marijuana).

Over to China Lake

Beta caryophyllene — regardless of source — is in the news this month because of Ben Harvey and his troop of advanced military fuel Tony Starks at China Lake, home to the Naval Air Warfare Center, Weapons Division. Now, they’ve have come up with an ultra-performance renewable diesel, and a high-performance renewable jet fuel candidate, made from that essential oil.

China Lake is a complete misnomer — there’s no lake and it’s not in China. In fact, it’s located on a pretty good candidate for “the most inhospitable strech of US Highway 395,” about 40 miles or so north of Edwards Air Force Base in the heart of the Mojave Desert.

China Lake Naval Base seen from the air — with its signature A-shaped runway design. It’s been rated as the 4th most highly classified military operation out there. Can you say S.H.I.E.L.D.?

There doesn’t appear to be much to do for fun in the area except invent transformative fuels with military applications.

About those transformative fuels for the troops

Let’s rewind for a review of the problems and opportunities. Right now, a tremendous amount of fuel flows out of the Middle East, and the US spends an estimated $99 billion annually to keep the global fuel sea-lanes open. Meanwhile, there are some unfriendly regimes, who obtain funding for considerable global mischief from selling petroleum or raising money from amongst those who do. The cost of that petroleum is highly volatile, making it tough for the Navy to control costs and assure a flow of money for training and operations.

For all those reasons, the Navy is looking for alternative fuels, focusing in the past decade on domestically-produced renewable biofuels. But in the Navy’s case, they’ve insisted on infrastructure-compatible, cost-competitive fuels. They’re happy to buy, but they’re not changing the ships and planes and not interested in paying more on an on-going basis. For research and certification purposes, they’ve bought test quantities at “minuscule quantities” prices — but that’s as far as it goes.

Recently and intriguingly, a new opportunity has been consistently cropping up in research. What if alternative fuels could be developed that not only meet the renewable, domestic, cost and infrastructure requirements — but actually outperform conventional fuels?

Could we fly faster, farther and carry bigger payloads than the bad guys?

That’s what the China Lake crew — and a small band of fellow researchers around the country — have been working on.  Think of them as the Fuelvengers.

There are two pieces of good news. One, as we observed in 2012:

Wright-Patterson [Air Force Base] tests had shown that renewable fuels were lowering engine temperatures by 135 degrees, owing to absence of impurities found in conventional fossil fuels. When those impurities burn, Omar Mendoza explained to The Digest. cause high temperatures to radiate throughout the engine, causing an acceleration in metal fatigue. He added that the preliminary data showed that engine parts could last up to 10 times longer, if the new high performance fuels were employed in place of conventional fossil fuels. He said that the tests showed that drop-in renewable fuels had, for the same volume, 7 percent less mass, which lowered the weight of the plane when fully fueled, and made it possible for the jets to fly faster, farther, or carry more payload.

But here’s the better news. Regardless of performance in the nozzle, there are super-dense terpenoids that can be used to make ultra-performing military fuels — both diesel and jet.

OK, we have to take a “short primer on engine science ” break, here, stay with us

On the diesel side, there’s been trouble with cetane numbers for some of the ultra-performing candidate molecules. Pinene and limonene, for example (yes, the source of the fragrance in pines and lemons) make for super-dense fuels, but they have ignition delays (reflected in the cetanenumber) that can cause underperformance, knocking and excessive engine wear.

Ovet at China Lake, the team has focused in on a blend of carophyllene and what’s known as a synthetic paraffinic kerosene. If you’ve heard of commercial flights using a “renewable jet fuel” it’s almost invariably, to date, a blend of SPK with conventional fuels. Bottom line, a proven fuel. In this case they’ve transformed b-carophyllene into a carophyllane isomer.

I know, this is starting to read like a science lesson instead of a story about high-performing military aircraft operating on fuels made from dope. We’ll get to that in a sec.

This article, published by the American Chemical Society in Energy & Fuels, concludes that a new diesel fuel can be made from a blend of 65% carophyllene and 35% SPK, meets all the performance needs of a diesel fuel, and has roughly 4% more energy content in the fuel. A new jet fuel made of 40% carophyllene and 60% SPK hit all the performance goals and equalled conventional fuel in energy content. You can get the full scoop here — keep your built-in, shockproof,  “replete with scientific terminology alarm” on, though. But the article is filled with valuable nuggets of hard data.

Essential oils vs industrial sugars

So, will we be flying military missions any time soon on dope? Industrial hemp is only being revived just now — so, probably we’re a ways off, if it ever happens.  And, keep in mind that there are 50,000 terpenes out there, with only 50-60 of them being found in our friend cannabis sativa. It’s likely that we will see other candidate oils step forward.

Although, you can make a case that military fuel makes a second, high-volume market for growers raising crops for the fibers or medicinal markets — and we’ve seen that model work, for example, with soybeans, where soy meal drives the market but leaves lots of volume of soy oils available for biodiesel or other applications. As one Digest reader put it recently — “It’s dead easy to commercialize. Give away the fuel. Sell the smoke.”

Alternatives to essential plant oils? Another path forward in the research is to make the required sequiterpene from industrial sugars. Amyris has a path forward for that — keeping in mind that their prized biofene molecule, farnesene, is a sesquiterpene too. In that case, their highly engineered microorganism ferments sugars into recoverable farnesene, which can then be cheically upgraded to an alkane, farnesane, via established methods.

A recent patent app by the US Navy team at China Lake covers both the oils-to-jet and sugar-to-jet pathways, and that’s here.

Eight Miles High

One thing to note. The latest research focuses especially on opportunities for military diesel fuel — used, for example, for non-nuclear ships. And especially focuses on boosting the cetane ratings for candidate fuels.

But cetane is a measure for compression ignition (diesel) engines, and doesn’t apply to turbine engines used for jets. In the China Lake patent app from January, we see even more exotic energy densities from some of the ublended fuels that would not be good candidates for diesel because of low cetane numbers.

At the high end, there’s HDCL-10, which checks in at 140,900 btu/gallon. That’s 12% higher than conventional jet fuel. In practical applications, think of this. An F18/A Super Hornet fighter has a gross take off weight of 26 tons. With 12% more energy in the fuel, you can fly 12% more payload for the same range, or fly 12% farther. Or, take 12% less pilots to complete the same payload mission.

And yes, those F18/A Super Hornets, indeed, do fly 8 miles high. Almost 10.

And that’s high flying indeed. Dope can pack some punch, especially if you burn it in an engine, not your own.