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Comment by throwawaymaths | Hacker News Reader

iirc it is scientifically possible to take corn stover and convert it to bioethanol with net negative carbon emissions.

There was a bunch of activity in the 2000s and 2010s trying and failing to do this commercially.

Never say never but for ground transport BEVs seem like they will eat the market well before anyone gets the technology working.

BEVs powered by PV use two orders of magnitude less land than ICEVs burning biofuels.

Biofuels are just incredibly land (and water) hungry. In the post fossil fuel age, biofuels will be reserved for special applications, if that (and for providing carbonaceous feedstocks for the organic chemical industry.)

> use two orders of magnitude less land

not if you use stover and cob. in those cases, you use net zero new land (you were growing kernels anyways)

Using a process that no one is using. Ethanol from cellulose failed.

Clearly. Worth asking why though, if it wasn't scientific (assuming my recollection is correct). Is it because of patents? Lost knowledge? Better alternative? Subtle engineering issue?

It was a technical failure, I believe. It was too difficult to hydrolyze cellulose and hemicellulose efficiently into a mixture that would allow enzymatic conversion to ethanol. Enzymes are easily poisoned and the mixture is more complex than what one gets from starch (which is just polymerized glucose.)

There is one success story, in Brazil.

https://pubs.aip.org/physicstoday/article/75/7/22/2848574/Wh...

Conversion of cellulosic biomass into chemicals other than ethanol might be the better route to take, particularly if green hydrogen can be used to boost the yield. Virent (which was bought out by an oil company) has a process for doing this. It would yield even more fuel per unit of biomass than conversion to ethanol, as potentially all the carbon can end up in the fuel. The fuel could also be drop-in replacement for existing hydrocarbon fuels. But there's not much interest in this as long as oil is still being used.

again i recall it wasnt technical, but i dont recall where i heard that (i could be wrong). they might also not have been doing enzymes, it might have been orgsnismal. do you have specific knowledge that this effort failed for technical reasons?

yes I'm aware. in that era, which was last i tracked this field, BP had a pilot plant that reached commercial and greenhouse breakeven, but then they lost the deepwater horizon case and scuttled their biofuels research, I'd be surprised if no one caught up. did no one catch up?

this is as much evidence as i can find on the internet that this was a thing, i cant remember where i heard that it was breakeven:

> BP sought to experiment with ways to turn corncobs, sugarcane and other agricultural waste into biofuel

https://www.nola.com/news/business/bp-shutters-biofuel-plant...

My thought is if the plant was on track to success but was killed by corporate politics somebody else would have tried again. The demand for carbon-neutral liquid fuels isn’t going away; long-range shipping and aviation aren’t going to run on batteries.

> somebody else would have tried again.

Yes. I would think that too. But the market isn't efficient, VCS are definitely not efficient, and it takes a lot of capital to spin up a factory, and the number of qualified people to run this factory is probably in the hundreds worldwide. Also ppl who worked on it in the past might be burned out, or not have access to key IP... Hundreds of things could get in the way

‘Demand’ in this sense is driven by economics + politics.

Nothing is going to beat fossil fuels on pure economics, so then we’re left with what political pressure will be applied and how much to make other options economic enough.

Biofuels are so marginal, it’s unlikely they’re going to ‘win’ as they would require exceptional political pressure and excluding a lot of other options.

There are people who use pyrolysis to turn left over biomass to biochar which can then be added to the soil and, depending on your energy use for other things, can turn the process carbon net negative. It is a roundabout way to sequester carbon though as you need to consider the opportunity cost of doing other things with the land (like leaving it for nature to take over and sequester carbon that way).

It's always worth being sceptical about some of these claims about processes magically being carbon net negative since cleaning up the atmosphere might not actually be what's paying the bills leading to inherent conflicts between selling a product (ethanol) and doing an environmental service. Switching to EVs will allow you to use much less land to fuel the cars with wind or solar energy and then the leftover land can be used for carbon sequestration and rewilding/biodiversity projects where that's the sole focus of the operation.

Yes

Deeper topsoil is a good way to sequester carbon.

Buffer maybe. Like forests, actual sequestration (beyond an initial ‘loading’ amount) isn’t a thing long term.

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