from Hacker News

Producing industrial hydrogen from biomass

by grantlmiller on 3/19/19, 10:44 PM with 102 comments

• by warent on 3/20/19, 1:39 AM

  "Obviously we just needed a steeper cone angle, so we fabricated one at 75° but it still jammed. Perplexed, we increased the angle to 82.5°—practically a straight pipe—and it still jammed. Thus began our surprise introduction to the field of bulk material handling, where entire books have been written and companies have been founded solely to solve this issue known as ‘bridging’, and the frequently-associated ‘hammer rash’."

  This is hilarious I think partly because it's such a common theme in engineering or life in general. For some reason things that initially seem so benign and straight-forward end up becoming absolute rabbit-holes of startling complexity.

• by torpfactory on 3/20/19, 12:59 AM

  Looks like they've got some bad Funnel Flow in the hopper. Mass flow is probably the desired flow regime. Using a non-conical hopper is probably a better idea and would negate the vibration, which can fail.

  Typically only change the shape of the hopper in one direction at at time as you move down. This often leads to hoppers with an exit that is a slot and not round.

  We've used these powder consultants before and I took a week long course on hopper design: http://powdernotes.com

  Edit - another method we use to create empty-able hoppers: fluidization. Not sure if this fits with your processing strategy but it also mixes the powder somewhat which prevents size segregation of the particles. And this video is pretty cool:

  https://www.youtube.com/watch?v=My4RA5I0FKs

• by ada1981 on 3/19/19, 11:40 PM

  My initial thought was vibration, so I was happy to see that was the solution!

  I’ve been in bed sick all day with a terrible cold and my sinuses are packed solid.

  I had a headache and so out of bordeum tried using my black and decker buffer to massage my head and relieve my headache (I use the buffer as an awesome massager and modded it with a variable speed switch).

  To my surprise it worked on the headache and also liquified my sinuses.

  A quick google search turned up a few other people playing with vibrators for congestion and at least one patent.

  Funny to come across this after experimenting with getting solids to behave at liquids via vibration all day.

• by thinkcontext on 3/20/19, 2:07 AM

  I'm skeptical of most bioenergy projects that involve growing things in a field. The best by far I've seen is seen is Brazilian sugarcane to ethanol. Sugarcane is around 8% efficient at converting light into biomass, for comparison corn which the US uses for ethanol is 1-2%. Of course you then have to process those into something else to allow us humans to make use of that energy, so real efficiency is lower.

  Compare that to PV solar which is around 18% in a form that humans can use. Of course electricity is more difficult to store than ethanol and hydrogen but there's a big efficiency advantage that has to be made up.

  Much better would be to use organic waste. People have to pay to get rid of that stuff so if you can make it your fuel there's money to be made. Hydrothermal gasification or liquification both seem promising for that.

• by throwaway5752 on 3/19/19, 11:47 PM

  So many questions.

  How much geological sequestration capacity exists, how long term is the sequestration, and what is the cost of securing it at the necessary scales? Is feedstock local to sequestration formations, and if not, has the transport been factored in?

  Why not biogas as a turbine feedstock and sell carbon neutral electricity on the grid (offsetting extracted hydrocarbon)?

  What about hydrogen being (my understanding) an indirect plastic byproduct?

  What was the drawback of monetizing bio char volatiles while selling the "waste" as a soil amendment products?

  I only ask these because I very much want this to succeed and I'm glad to see this here. I get the feeling that the point is very much finding an economic basis for sequestration.

• by mchannon on 3/20/19, 2:59 AM

  I get the desire to turn biomass into vehicle fuel. I don't get the desire to involve hydrogen.

  Biomass-derived syngas has to be substantially better in energy density and efficiency than any kind of hydrogen.

  The leading industrial use for hydrogen is in oil refining, so if you outcompete conventional steam reformed hydrogen on price, you're just going to make gasoline cheaper.

• by ars on 3/19/19, 11:38 PM

  This article is about getting chopped up grass to flow through a hopper (so that it can be gasified for fuel).

  If you want to read it don't get stuck at the top (the start makes it seem like the article is about gasification instead), keep going till the images start.

  Side note: From read this article they desperately need some experts. They are re-solving solved problems, and not working on what their startup is actually about. (I should add that them seem to be aware of this.)

• by mojomark on 3/20/19, 11:01 AM

  In case anyone is curious as to how bio-gassification compares to electrolysis (or a hybrid process), I found this 2009 paper [1] that sums it up decently (at least with the technology available at the time):

  (Note: SEK := Swedish Krone; currently ~$0.11USD and was roughly the same in 2009)

  Abstract: "An integrated system for the production of hydrogen by gasification of biomass and electrolysis of water has been designed and cost estimated. The electrolyser provides part of the hydrogen product as well as the oxygen required for the oxygen blown gasifier. The production cost was estimated to 39 SEK/kg H2 at an annual production rate of 15 000 ton, assuming 10% interest rate and an economic lifetime of 15 years. Employing gasification only to produce the same amount of hydrogen, leads to a cost figure of 37 SEK/kg H2, and for an electrolyser only a production cost of 41 SEK/kg H2. The distribution of capital and operating cost is quite different for the three options and a sensitivity analyses was performed for all of these. However, the lowest cost hydrogen produced with either method is at least twice as expensive as hydrogen from natural gas steam reforming."

  In addition to a dollar-to-dollar comparison, however, I think a Carbon-to-Carnon byproduct comparison is also warranted. If you don't have to pay for geo-sequestration (or the messy supply of grass compared to piped in water), is the small cost increase of electrolysis over bio-gas more than compensated for?

  As an H2 advocate myself (as an industrial transportation battery alternative), actively looking to boost H2 fuel supply infrastructure, I would be interested to hear from Chimere (OP co-founder) on this point. I ask, because I don't know the answer.

  1.) https://www.sciencedirect.com/science/article/pii/S036031990...

• by zawerf on 3/20/19, 12:09 AM

  I remember seeing a video demoing how to make sand flow like water by bubbling air into it: https://youtube.com/watch?v=My4RA5I0FKs

• by cwkoss on 3/19/19, 11:43 PM

  I was just talking with a coworker about how we could theoretically modify our espresso machine hopper to avoid blockages. This is a great survey of bulk material handling options.

• by gus_massa on 3/20/19, 3:08 AM

  How advanced is the hydrogen production prototype?

  Looking at the Wikipedia page https://en.wikipedia.org/wiki/Steam_reforming this looks like a difficult process, even when using methane that is a very small molecule and is easy to purify. Big molecules in grass are more eager to produce soot that would block the machine, and grass also has other elements like Nitrogen and Phosphorus that may react with the catalyzer, and there is the ash problem.

  Is using a grass more efficient that burning the grass and use the energy to produce Hydrogen with the standard method?

  What about producing ethanol from the grass and then using the ethanol to make the Hydrogen? (Both parts are somewhat proven technology.) And ethanol is easy to move and purify than grass.

• by jacknews on 3/20/19, 12:05 AM

  "With the addition of geological carbon dioxide sequestration it becomes carbon-negative."

  LOL, easy peasy then

  Can you make "grass charcoal"? If so, just pile the grass high and cover in a layer of clay before burning, as is done with wood. Then bury the charcoal, which also improves the soil

• by malloryerik on 3/20/19, 1:31 AM

  If you want to have the grass flow like water, could you take a stream of water and add grass to it? The water could carry it down a wide pipe for example, you filter the grass from the water at the destination, then send the water back to get more grass?

• by gdpgreg on 3/20/19, 1:37 PM

  Looks like the issue is the feed stock, non-uniform particle size distribution and significant differences in aspect ratio. All the different pieces are clumping up because of the particle interlocking. Maybe consider a grill sorter on the outlet of your size reduction system, allow <1cm particles through and rehandle larger particles back into whatever is chopping, or add secondary size reduction.

• by NoblePublius on 3/20/19, 12:35 AM

  Where is the evidence that carbon sequestration works?

• by hourislate on 3/20/19, 2:08 AM

  Couldn't they use a manure spreader to throw the grass onto a conveyor belt at a steady rate? Manure spreaders come with variable flow rate and beaters to shred the manure. If you threw a bale of hay in there it would tear it up and throw it nicely.

  Here is an example:

  https://www.youtube.com/watch?v=YhvMMK91P-8

• by vlizz on 3/20/19, 5:10 AM

  Is there a reason you need to make it flow as opposed to simply conveying it mechanically? It seems like you came up with a complicated solution (making solids behave like liquids) when there are plenty of simpler solids handling techniques that could be used. For example a belt or screw conveyor.

• by L_226 on 3/20/19, 10:25 AM

  I like this. Slightly related, I am planning on building a house eventually and I really want to incorporate a domestic biogas generator for cooking. Something like https://www.homebiogas.com/

• by snappr_ on 3/20/19, 12:58 AM

  Can the ash be used as a concrete additive?

  https://precast.org/2010/05/using-fly-ash-in-concrete/

• by dosy on 3/20/19, 1:15 AM

  you want to mix the grass with air so you have grass suspended in a flow of air just like a fluid. since you need to avoid oxygen blow this grass nitrogen suspension through some pipes and into your gassifier.

• by vixen99 on 3/20/19, 10:49 AM

  'Charm’s mission is to return the atmosphere to 280 ppm CO2 profitably'.

  i.e., 2,130,000,000 metric tons of CO2 (= 1ppm) * (410ppm - 280ppm) or some 276 giga tons. Evidently a modest goal.

• by metalgearsolid on 3/20/19, 12:55 AM

  I would have loved to be there the moment they first tried a funnel and failed. Bulk material handling seems pretty interesting to solve.

• by SubiculumCode on 3/19/19, 11:43 PM

  I wonder what dampening the grass might do, as this might reduce the volume of the grass (increase density).

• by ggm on 3/20/19, 12:56 AM

  what % of the generated H2 is currently consumed by the sequestration?

  If no other energy source is available, does this % change?

• by mrfusion on 3/20/19, 2:55 AM

  So how does the sequestration work?

• by trickstra on 3/20/19, 7:43 AM

  wouldn't it be easier to pelletize the grass before feeding it?

• by naringas on 3/20/19, 2:00 AM

  why not blow the grass?

• by kazinator on 3/19/19, 11:44 PM

  > Naively, we assumed that grass would flow somewhat like an ideal fluid,

  Perfect sustenance for spherical cows.

  > allowing us to use a simple, funnel-like hopper.

  But, since that one didn't vibrate, it could hardly be called a grasshopper.