Pell-Mell at NREL : Two Bio Breakthroughs at the National Renewable Energy Laboratory

October 25, 2021 |

Found in the Bargain Bin of Overlooked Breakthroughs at the National Renewable Energy Laboratory, a team of researchers have programmed a microbe to make acetate or ethylene from CO2 and, wait for it, use not only photosynthesis, but electricity supplied from the plug point on your wall.

There are lots of reasons to get jazzed up, but think of it this way, organisms are doing well if, using photosynthesis, they can utilize 3 percent of the incoming light that shines on them. Top-shelf solar panels can get 17 percent.

Think of a plant as a vending machine that rejects 97 out of every 100 quarters you feed to it, now, there’s a pathway to use as many as 17. More plays, more pays, as they say in Vegas — only, in this case, the environment wins, because the process uses CO2. 

The breakthrough

So, here’s what our intrepid team led by Jeffrey Blackburn and Wei Xiong did. Knowing that plants have two systems inside them for photosynthesis, and that the second doesn’t play well with others, the genetically engineered cyanobacteria to shut down the pathway and then snapped the re-imagined cell to the cathode end of an electro-chemical circuit. There’s quite a bit of spooky science in how they handle the system — the molecular equivalent of a lot of tab A – slot B undertakings. 

Bottom line, you take excess solar or wind energy — and, you’re already thinking “Power-to-X, I know, well done you — and you make acetate or ethylene. Which is to say, when you’ve polymerized the ethylene, you’ve stored the solar energy inside glad-wrap, which the world pays good money to own. Reduced need to build expensive energy storage that you have to pay for as an expense, less risk of shedding valuable energy, and now we have an extremely low-carbon path to ethylene.

About scale

OK, where’s scale, you ask. This is early, early, early-stage stuff, so don’t look for it when shopping for Glad Wrap next week (“Now, with Solar!” will probably be slapped by marketing on the packaging when the day comes). Point is, the researchers have figured out how to do it, now they can work on scale-up. 

This work came out in a journal hardly anyone reads a month ago, perhaps because they propose to charge you fifty five dollars to read a single-article which is based on research which, if you paid taxes, you probably funded.  As the saying goes, no representation without double taxation, or did I garble that?

Also at NREL

In the NREL equivalent of the James Brown’s Celebrity Hot Tub (it’s hot, so hot!) is another breakthrough, this one considerably farther down in development, in short, a complete process.

This team here developed a fully integrated process to produce a promising precursor for diesel and jet fuel from cellulosic biomass, and the team estimates that their biomass-derived butyric acid can be sold at 55% of the current selling price of petroleum-derived butyric acid. 

Especially good news when you see that oil has crept up over $80 a barrel, again. 

The process established by NREL team is energy-efficient and results in a 50% reduction in greenhouse gas emissions compared to traditional biological production routes. Right now, they’ve moved on the scale-up, but they do have a process, that’s fine progress.

The backstory

The precursor, butyric acid, is normally derived from petroleum-derived propylene. Globally, approximately 80,000 tons are produced each year and sold at a price of about $1.80 a kilogram. 

What is butyric acid, anyway?

Ever smelled rancid butter. That’s it. Also in vomit and body odor, while we’re enumerating. Perhaps surprisingly, it;’s used as a flavorant, in industry. And in the manufacture of paints, coatings, and lots of things you might also use acetate for. 

By the way, some fish love it, apparently. It’s used in carp fishing bait as a base. And it’s tossed in the general direction of Japanese whalers by environmentalists to drive them away from their whaling grounds. As Monty Python might have put it, 

“I don’t want to talk to you no more, you empty-headed whale-guts-wiper. I Butyrize in your general direction. Your mother was a hamster, and your father smelt of elderberries.”

About that precursor thing

Only one slight complication here, does anyone really use butyric acid on a regular basis to make diesel and jet fuel? Just sayin’, no one’s ever going to use it as a precursor when it costs $1.80 a kilo, which works out to, depending on your fuel oil of choice, around $5.87 a gallon as a feedstock starting point. 

It’s very good news that we can make it for 45% less using a bio-based route. Nevertheless, we’re down to $3.28, or around 40 cents per pound, which is about the price of pretty decent white grease or soybean oil.

It’s also very good news that we can make this from lignocellulosic biomass. That’s extending the range of available feedstocks, brava!

Nevertheless, we probably should be chatting about butyric acid as a chemical precursor as opposed to a fuel precursor.

Why are we even hearing about “jet fuel” and “diesel” from NREL on this, anyway?

We’ll make an educated guess that we’re seeing “jet fuel” and “diesel” in the description of the breakthrough for pretty much the same reason that you almost never had heard those words in the same sentence as butyric acid for, say, the last ten years. Which is to say, fuels are in vogue again. Not to mention, the research was funded by the US Department of Energy and conducted by the National Renewable Energy Laboratory. Hint hint. It’s become obligatory, it appears, to city “diesel and jet fuel precursor” in DOE-funded liquids research since 14 nanoseconds after President Biden set a goal of “3 billion gallons of jet fuel by 2030”.

I might cite a few other precursors for diesel and jet fuel, through the miracle of gasification and separation: old sneakers, mother’s pearls, paper money you can’t use anymore like German marks or French francs, dog-doo, the portions of last night’s dinner that went uneaten, the Spirit of St. Louis hanging in the Smithsonian, and every contract that is not worth the paper it’s written on. 

One of the days someone will wave their magic Build Back Better wand in Washington and create a National Renewable Stuff Laboratory, to explore the production of renewable chemicals and biomaterials in their proper sphere.

Not that we don’t like butyric acid. We love it! Just not to make fuels.

The technical approach

In undertaking the research, the scientists evaluated microbes already able to produce butyric acid from biomass sugars. Very few have been studied for industrial applications. They considered two bacteria—Clostridium tyrobutyricum and Clostridium butyricum—that are able to ferment the two primary lignocellulosic sugars, glucose and xylose, and generate butyrate, acetate, carbon dioxide, and hydrogen as major products.

Using corn stover as the biomass, the researchers compared the performance of the two bacteria and determined C. tyrobutyricum better able to produce the precursor. Researchers further developed an advanced fermentation process wherein butyric acid is continuously extracted from the fermentation vessel. This process—termed by the authors hybrid extraction distillation – in situ product recovery (HED-ISPR) process—showed a “promising path” for converting biomass to butyric acid as a chemical intermediate for the production of renewable fuels.

Reaction from the stakeholders and the link to the paper

“The production of fuels from biomass is critical to diminish our reliance on petroleum and build a sustainable bioeconomy,” the researchers noted in a new paper outlining their work.

The paper, “Process intensification for the biological production of the fuel precursor butyric acid from biomass,” appears in the journal Cell Reports Physical Science. The authors, all from NREL, are Davinia Salvachúa, Patrick O. Saboe, Robert S. Nelson, Christine Singer, Ian McNamara, Carlos del Cerro, Yat-Chen Chou, Ali Mohagheghi, Darren J. Peterson, Stefan Haugen, Nicholas S. Cleveland, Hanna R. Monroe, Michael T. Guarnieri, Eric C. D. Tan, Gregg T. Beckham, Eric M. Karp, and Jeffrey G. Linger.

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