Of Flying Peaches and Barrels of Monkeys: The quest for sustainable flight by world-scaling a neurotransmitter

October 8, 2018 |

The fact that you are reading this makes the case for “reasons to love carbon monoxide”, because the molecule works as a neurotransmitter (conducting signals around the nerve system) and plays a role in keeping your heart beating.

So, if we have a carbon monoxide problem it is the problem of having too much of it, in the wrong place, and not much to do with it at the point of production. As in steel mills or tail pipes.  And that’s the story of the bioeconomy in some ways  — the search for ways to use the things we have too much of, so that we can stop using the things that lead to imbalances — environmental, social or economic.

Last week, we reported in the Digest that a Virgin Atlantic commercial flight took off from Orlando and flew to Gatwick on a blend of a petroleum and a stupendously clever new fuel  — made from carbon monoxide waste gases from a steel mill in China – and scaled up to commercial production. That Sir Richard Branson was at Gatwick to greet Virgin Atlantic CEO Craig Kreeger and LanzaTech CEO Jennifer Holmgren as they emerged from the plane — along with roughly 280 passengers who were pleasantly startled to find themselves in the midst of a step forward for sustainability. The volumes were small, it’s a first commercial flight: what matters is the path forward, which begins with commercial-scale production of this fuel by 2020.

The story goes back to a group of pioneering scientists, mostly out of Chicago and Washington state, who over a period of years would shuttle in and out of rural southeastern Georgia, to build a process to convert Lanzahol — that is, ethanol made from steel mill off-gases — into LanzaJet. They became known as the Flying Peaches, and the process they came up with — dehydration, oligomerization, hydrogenation and fractionation at what is known as the Freedom Pines Biorefinery in Soperton, Georgia — that’s the real star of the Virgin story. Branson’s well-known megawatt charisma notwithstanding.

Let’s look at how they did it, and especially we’ll look at the oligomerization, that’s the tricky part.

Ethanol to ethylene: dehydration

You may not know it, but chemically speaking, a glass of wine is basically Glad Wrap and water, which is to say that if you dehydrate the water out of ethanol, you get ethylene. Now, if you’re planning to change water into wine, tossing in some Glad Warp at room temperature and stirring won’t actually get the job, but you get the idea. 

So, dehydrate your ethanol into ethylene, and just for the moment set aside all that good clean pure water for a moment; don’t sell it just yet to Dasani. Although, just saying, you could hardly find anything as clean and fresh as water produced from ethanol (the alcohol kills off the microbes).

With ethylene, you’ve made a good start, because ethylene is a hydrocarbon and that’s what jet fuel is, too. But jet fuel is kerosene and we are miles from 10-14 carbon kerosene with our friend, two-carbon ethylene.

Oligomerize

There ought tot be a spell in the Harry Potter book series for oligimerization, because the world could surely use a magic process for this step that makes longer-chain hydrocarbons from short-chain ones.

Oligomutansis! cried Hermione

Oligomutansis! said Hermione.

For now, we’ll have to rely on the Flying Peaches and a group of researchers at the Pacific Northwest National Lab who came up with a unique oligomerization step.

There’s a long explanation and shorter, peppier one.

The long explanation starts thus:

Currently a need exists for alternative hydrocarbon fuels, especially aviation and diesel fuels, from domestic sources to enhance energy security and to decrease reliance on foreign petroleum. Current routes to alternative fuels are limited by strict fuel standards and limited fuel feed stocks…Ethylene is a feedstock available from numerous sources that could be converted to alternate open-chain hydrocarbon fuels…Ethanol…can be considered an ethylene precursor. However, conversion of ethylene via conventional direct, single step conversion processes catalyzed by solid acid catalysts, such as silicoaluminates, is typically characterized by high process temperatures (>280.degree. C.) that form large quantities of coke, and extensive formation of aromatic compounds up to 70 wt %. Single-step processes such as that reported by Heveling et al. over Ni/Si–Al and other catalysts are reported to produce open-chain hydrocarbons at high ethylene conversions, but with selectivities to .gtoreq.C10 of only ca 40% and to .gtoreq.C8 of only about 63%. Further, multi-step conversion processes reported in the literature have potentially better selectivities to open-chain compounds, but conversions to date are low and significant quantities of aromatic compounds are produced. For example, Synfuels International reports a multi-step process using Ni catalysts at process temperatures from 220.degree. C. to 240.degree. C. that produces a product composition containing between 4% to 90% aromatics. At the reported maximum selectivity of 70% middle distillate products and an ethylene conversion of only 26%, the maximum possible product yield in the middle distillate range is only about 18%. The 2-step Synfuels International process does not improve upon and, in fact, gives a lower distillate yield (18%) than the 1-step process reported by Heveling (40%). Thus, the 2-step approach by Synfuels International does not represent an economically feasible approach for obtaining high yields of distillate fuels…The present invention addresses these needs using, surprisingly, a 2-step method that provides distillate yields greater than the 18% of the prior art. 

And you can read all about it here.

The Barrel of Monkeys game

For the short explanation, let me refer you to the Barrel of Monkeys game. You may remember, you have a small barrel of plastic monkeys, and you have to link them together into a long chain, by picking them up one at a time using the one monkey to gran the second, the chain of two to gran a third, the chain or three to grab a fourth, and so on. Think of the short-chain molecules as the monkeys, and as an inorganic catalyst as the molecule that catches the monkeys and spins one into a connection with the others. 

And, thus we arrive at long-chain hydrocarbons.

The catalyst can be tuned so that what is produced is a diesel-jet mix that can be anything from 90/10 jet to 70/30 diesel. It has to do with the length of the carbon chains. Anyway, we’re going to end up with some of each. And that means we have to separate those two types of fuel. We’ll come back to that shortly.

For now, we have a small problem to overcome. Now, we have unsaturated hydrocarbons. If you’ve been reading about saturated fats and unsaturated fats and transfats in the health and nutrition debate, you have the basic knowledge you need, already. There are unsaturated molecules and saturated ones, they behave differently, and kerosene is a fully saturated hydrocarbon, so now we need another step.

Hydrogenation

That’s hydrogenation, which you might remember from the food shelf, because those are the creamy fats, which are more stable, and that’s good for shelf life, but they contain transfats, and that’s bad. None of which has much to do with kerosene because, for goodness sakes, no one drinks it. But you get the idea that there’s this step called hydrogenation, and basically we grab some loose hydrogen and treat the fats until they are saturated, which is to say that everywhere you can connect a hydrogen atom to a carbon atom, you have done so. And we can do that with hydrocarbons as well.

Now, about that loose hydrogen lying around. The sun is completely replete with it; in fact, it’s the most abundant element in the solar system and there isn’t even a close second.

But, try and grab some. And that’s when we run into the “cost and temperature of landing hydrogen miners onto the surface of the sun” problem, as it is definitely not known in academic circles. However you limn the term, standalone hydrogen is not freely available in pure form here on the good earth.

However, there’s good news. Remember all that water we set aside in the dehydration step? Yes, we’re net positive on water, and we can split that into hydrogen and oxygen. Presto, we have hydrogen.

Last step

The Freedom Pines biorefinery in Soperton, Georgia

Above, I mentioned that we end up with some diesel-range and some kerosene-range molecules in our mix. Now, we have to separate those — that’s fractionation. Happily, that’s a well understood step (usually, distillation, as the two fuels have different boiling points). One of the reasons that a lot of biorefineries and all petroleum refineries have these giant distillation columns.

And there we have it. Fermentation. Dehydration. Oligimerization. Hydrogenation. Fractionation. Perfectly good jet fuel as a propellant, extraordinarily low-carbon, and brought to you by a whole bunch of bright thinking by those Flying Peaches down at Freedom Pines.

All from carbon monoxide as the carbon source. Recaptured carbon. It’s extraordinary, really.

So, we know should make sustainable fuels.. And now, we know that we can make them.

But will we make them?. That’s where Virgin Atlantic comes in, and so long as the cost is reasonable and that has a lot to do with scale-up and supply chain building and solid policy — all things furiously underway around the world, we might have something we really can use. Sourced from carbon monoxide we couldn’t use (except in those very minute quantities, such as out bodies learned so long ago in designing the brain and the nervous system and, well, us).

The Carbon opportunity

For some time there’s been too much of a debate over what is a biofuel, are biofuels useful and viable, and so forth. It’s a crazy debate, in the end. All fossil carbon has an organic origin, and all biogenic carbon has a fossil element these days. You can’t find a tree or plant that hasn’t used some petroleum-based carbon to make its leaves, or a barrel of oil that at some point in history wasn’t a pool of plants or algae. Solar and wind technology use fossil energy and so do electric motors. The pursuit of pure solutions is a search for unicorns.

The other way to go is to seek to make the very most out of every molecule of carbon we have — it’s the one-and-done attitude of “dig, refine, burn, vent” that has us lined up for a climate change catastrophe.

Capture and re-use. That’s what plants do — they capture carbon from where they can (and they don’t turn down carbon just because it came from petroleum, at some stage). And re-use. Every molecule used twice is a fossil molecule that stays in the ground. The trick is to avoid venting, thoughtlessly. It’s a good rule for dinner table conversation, too.

The carbon monoxide opportunity

Bottom line: carbon monoxide is a really great thing if you know how to capture and use it. And that’s what is great about recapturing carbon. It makes you think more deeply about the carbon around us. Peaches that fly, barrels of monkeys, a process we use to make margarine — you just never know what will become useful in the world of the advanced bioeconomy.

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