Comment by mchannon | Hacker News Reader

Comment by mchannon | Hacker News Reader

Parent Full thread

(1) You should check out https://wcroc.cfans.umn.edu/wcroc-news/ammonia-wind (the title specifically mentions "gaining momentum"). (Bear in mind this technology works by making H2 first from electrolysis). There's a half-dozen more of these research groups. Wind and solar electrolysis are sensible because they can be placed next to ammonia consumers that currently have to have ammonia shipped in from thousands of miles away. Unfortunately, your technology is tied to CO2 injection wells, which aren't all that common outside the western US.

(2) I'd love to see your math, but assuming it's not available, let me show you my math: Assume 6000 pounds per acre per year yield of wet grass. Say that's 5000 pounds dried. Model grass as 100% cellulose, which is 6% by weight hydrogen. Assume 100% process efficiency, where you get all the hydrogen out, and it's magically compressed. 300 pounds of hydrogen sounds like a lot, but according to wikipedia, is only worth about 32 cents a pound at the pipe. So my numbers show $100/acre/year. The value goes way up at the "pump", but that's because of transportation infrastructure that neither you nor your competition provide. That also assumes free injection of low-pressure waste CO2, which is not only a fantasy, but presumably ties your process to a location far away from your target market for the H2.

(3) Ammonia solves your hydrogen storage and transmission problem, so my math shows it's way favorable, especially since you're triply tied to a CO2 injection site, fertile acreage to grow your grass, and an H2 consumer. Picking ammonia makes cost-effective transportation to the consumer possible. Realistically, you'd react the ammonia with CO2 to make urea, which is way better than ammonia for both transportation costs and market demand.

(4) Didn't say YC funded you, but you were in their demo day, hence my mention of the YC slot.

(1) When we investigated this last year the ammonia synthesis capex looked untenable and we didn't see a path to lower that capex. Re:injection wells... they are super common in Texas/Louisiana region as well, which happens to be where most of the US refining capacity and ammonia production is located, so we're very near customers there.

(2) 6000 dry lbs/acre/year = 3 dry tons/acre/year which is an extremely low yield. Even miscanthus and switchgrass get over 10 dry tons/acre/year, energy cane gets to 20 dry tons/acre/year and our grass gets to 25+ dry tons/acre/year. So that brings your $100/acre/year up to $800+/acre/year. Then for the chemistry it's important to note that much of the hydrogen gas produced is actually coming from H2O that reacts with carbon in the cellulose to produce 2 H2 + CO2. So, stoichiometrically you get significantly more than the elemental hydrogen content of the grass itself. That gets you another factor of 2 or so... and then we're at the $1750/acre/year mentioned in the parent comment.

(3) Agreed the transportation costs are better for ammonia, but we aren't actually transporting the hydrogen except over a feeder pipe into a refinery or ammonia plant. It's cheaper and simpler to transport the grass as opposed to the hydrogen, mostly because you get to avoid the pre-transport compression energy and losses. Again, as in (1) the issue with ammonia is the heavy capex based around Haber-Bosch pressure vessels and compressors... we didn't have any good ideas for reducing those costs, so there's no sense in competing there.

(4) We weren't at YC's demo day... not sure what you're referring to ¯\_(ツ)_/¯

(1) Since you're limiting yourself to the gulf region, it'd probably be responsible to disclose your CO2 injection costs, including the cost of compressing the CO2 to the necessary pressures. It'd also be responsible to either disavow or embrace enhanced oil recovery vs. other injection approaches: you're either devoted to reducing carbon or making gasoline cheaper, and you have to choose.

(2) If these numbers are accurate, you're doing yourself a disservice by burying them. 25+ dry tons/acre/year is amazing. And I thought the crab grass on my lawn grew fast. I seriously doubt your chemistry, however. Let's look at your three possible approaches (2b sounding the most like what you're claiming to do):

(2a). Charring: Hopefully using all that free low-grade heat from the refinery you colocate with, the cellulose cooks until all the hydrogens join with the ample oxygens in the cellulose and you end up with a char and steam. No hydrogen this way.

(2b). Steam Reforming: This tech works with natural gas because the C:H ratio is so low, and no oxygen is introduced that doesn't bring its own "dates". Because the C=O bond in carbon monoxide is so strong, you can leach off some of the H2. However, as soon as you raise that C:H ratio, or up the available oxygen, steam reforming fails and just becomes combustion. C:H in cellulose is 6:10 vs. methane's 1:4. And that's before the 5 oxygens (vs. methane's 0) ruin it further. No hydrogen this way.

(2c). Fischer-Tropsch (the original Hans and Franz): In a chamber about as expensive as your Haber-Bosch capex, you somehow convert dried grass and catalyst to a mix of H2 and CO, the latter of which you can convert into more H2. Doesn't sound like you're using this approach, though it could technically work if pressure cooking your grass didn't require ridiculous amounts of energy, and you had a way to separate the H2 from the syngas. How many MJ of energy is that? So, maybe Hydrogen this way.

(2d) What'd I miss?

(3) Ok, so your co-founder's protestations about making gasoline cheaper were unnecessary, and you co-locate with oil refineries. Instead of downplaying it, own it: grassoline is trademarked but not for the type of product you'd make. Makes sense to leverage someone else's existing capex, as long as they let you. Those oil guys are flush with cash, why are you distancing yourself from them? They'd love to have your CO2 if it's at high enough pressure.

(4) My mistake. Your timing was highly coincidental with Demo Day, technology looked like it could have been part of it, and the faulty assumption was mine.

Reply on news.ycombinator.com