Bacteria upcycle carbon waste into valuable chemicals | Hacker News Reader

Bacteria upcycle carbon waste into valuable chemicals

news.northwestern.edu

79 pointsgmays23 comments

The journal article: https://www.nature.com/articles/s41587-021-01195-w

The valuable chemicals are acetone and isopropanol. (Not being snarky--they are indeed of value so if we can make their production an affordable carbon-negative process, that's pretty nifty.)

The term "carbon negative" is getting overused a lot, and this is one example...

The carbon is not removed permanently, it's stored in products that will eventually end up in an incinerator causing CO2 (or worse, on a landfill, where their degredation may cause even more harmful greenhouse gases).

Regardless of the nuances of what "carbon negative" exactly means (and I agree it often gets misused), everytime we move a process off of using coal/oil/gas and onto using carbon that's already in the atmospheric cycle, that's a win in the fight against climate change.

Yeah, this gets missed a lot in conversations about climate but it's crucially important: the carbon cycle is a necessary part of the environment - the way we're messing it up is by emptying a long-held buffer of carbon (fossil fuels), and emitting carbon faster than it can be reabsorbed, while diminishing the reabsorption process through clear cutting, soil erosion and ecosystem destruction. Producing some CO2 is inevitable; we need the amount to be sustainable, the cycle to be balanced, and to stop emptying large carbon buffers. We can use hydrocarbons if they're made of atmospheric CO2. if anything, they serve as a temporary buffer, like a CO2 cache.

I really need to get round to starting my blog on cybernetics and system dynamics one of these days; I see these kinds of misconceptions all the time across so many subjects.

Well actually … I see these kinds of well actually forest for the trees statements all the time.

Anyone who has studied global warming or taken any science class already knows about the carbon cycle.

You probably see them in response to people saying that renewable carbon processes are bad because of CO2. Which is the erroneous view that I was correcting.

You and I may know about the specifics of the carbon cycle that are being overloaded, but clearly GP was applying an incorrect mental model. Which, even if you know about the carbon cycle, you can do.

You don’t have to remove co2 permanently to be useful, for instance, each individual tree may eventually become gas again, but if you double the size of the forest, you’ve doubled the amount of gas not currently in the atmosphere. As long as that forest exists, that carbon is captured, even as individual trees get swapped out for their gaseous counterpart.

I wonder what the cost is compared to the current process? I also wonder which chemicals they'll target next.

From the paper:

> Chemical and energy inputs and product yield were determined using pilot-scale data coupled with design data from industrial-scale ethanol production, which uses steel mill off-gas feedstock with utilities (for example, electricity and steam)

> The GHG emissions of acetone and IPA produced by the gas fermentation process (Fig. 6c) are −1.78 kgCO2e/kg acetone and −1.17 kgCO2e/kg IPA, respectively. The negative value is due to avoided off-gas emissions combined with low process emissions (Fig. 6c), effectively locking carbon into the product.

> After transformation into C. autoethanogenum strain, the resulting acetone combinatorial strains were subjected to Schott bottle growth on 1.5-bar synthetic gas blend (50% CO, 10% H2, 30% CO2 and 10% N2; Airgas)

I wonder what sort of energy is required to generate that sort of gas mixture from atmospheric CO2 concentrations (0.0412% these days), and whether the CO and H2 are essential. It looks like that (and the 1.5-bar pressurization) are the only substantial energy inputs to the process.

Or, alternately, I wonder how many tons of such a mixture are industrially produced currently.

I'm 100% in favour of carbon removal through whatever sustainable means by which we can achieve it, but if we succeed, and carbon levels start to fall, I've got this nagging concern.

What happens in (say) 200 years, when our entire industrial base might be dependent on products created from atmospheric CO2? Is it possible that there won't be enough CO2 left for plants to grow? (I know there would be other very serious consequences as well, if atmospheric CO2 gets too low)

If there ends up being money in CO2 removal then how do we ensure CO2 levels remain in the habitable range, and that we don't just keep removing CO2 because doing so is valuable?

There appears to be a fundamental economic driver for climate change, which we are probably going to address using the very same economic driver that got us here in the first place.

(Admittedly, worrying about the world in 200 years seems a bit of a stretch at this moment in time).

I think, generally, making CO2 is pretty easy. There are billions of things that make it as a byproduct and that's why we have a problem with runaway CO2.

Things that consume CO2 are less common.

But that is a good thing to think about. We don't know what industry will be like 200 years from now. I guess boring deep into the earth for methane and other gases to burn would be one way. No matter what happens, resources on this earth are limited, though.

I hope that in 200 years we are well past the notion that government can't regulate these kinds of things. If not, we might not even be around that long as a civilization.

The carbon doesn't disappear. If you can go from CO2 to C then you can recycle it.

First sentence in the article:

> Bacteria are known for breaking down lactose to make yogurt and sugar to make beer.

Why do they do this? Yeast makes alcohol, not bacteria. The people that research this stuff probably know this, so why do they feel the need to dumb stuff down for readers? It is frustrating.

Sour beers exist, but yeast is definitely still the microorganism responsible for the alcohol content. I'm guessing the article itself wasn't written by the researchers, though.

they're referring to lactobacillus which produces some of the flavors in bread, beer, wine, yogurt, miso, kimchi from sugars, such as lactose.

Nothing matters unless and until it scales. There are scores of these little examples of doing this sort of thing in a lab.

Surely the converse is true: nothing ever happened at scale which didn't start off as a little example on a lab bench?

The vast majority of the living things on Earth didn't start off on a lab bench, they just mutated and evolved "out there," in nature.

Therefore the converse is not true.

Mutations don't happen at scale, they occur in single organisms. Therefore the converse is true!

And this is a useless, low-effort point to make. If we waited for a technology to scale before posting about it on HN, it would already be old news.

The cautionary statements occasionally make sense for announcements around battery tech in particular. Here I agree it’s not useful

I think the publication describes they scaled it to a 120L pilot reactor and ran the process continuously for 3 weeks feeding it 11 to 23 L of gas per min.

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