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There are other ways of generating electricity apart from electrolysis. For example, from food waste through yeast and other methods. Yes, there is some energy

• xyzzyz 6y ago
  > For example, from food waste through yeast and other methods. How is it better than generating biogas from biomaterial, something we already do at industrial scale? What’s the advantage of biohydrogen over biomethane?
  • weswpg 6y ago
    isn't methane much worse for the environment than generating power from hydrogren?
    • ncmncm 6y ago
      It depend where the (carbon in the) methane comes from. If it comes from the ground, the exhaust contributes to global climate disruption. Venting methane is worse, but that would be wasteful, too.
      • godelski 6y ago
        It also depends where the hydrogen comes from. If you produce it from water, your byproducts are oxygen. If you produce it from methane, your byproducts are carbon dioxide. Issue is that water has 2 hydrogens and methane has 4, so typically it is produced by using methane.
        • xyzzyz 6y ago
          Issue is that water has 2 hydrogens and methane has 4, so typically it is produced by using methane. It’s not really about that, we don’t lack water or methane. The issue is rather about the energy required to produce given amount of hydrogen. Electrolysis requires 2-3 as much energy as steam methane reforming already if you just look at energy of chemical reactions, and moreover, steam reforming requires just heat, while electrolysis requires electricity, which again is more expensive than heat: we produce most of our electricity from heat, and the conversion efficiency from heat to electricity is around 20-30%, so it makes more sense to use all the heat directly instead of going through electricity production stage.
          • ncmncm 6y ago
            1. Electricity is getting cheaper all the time. The cheapest forms, wind and solar, involve no detour through heat. Anything that uses electricity instead of something that produces CO2 is a big net win. 2. Huge efficiency gains are to be had, in electrolysis, via catalytic action, needing only transition from lab to production funded by sufficient demand for the hydrogen. 3. There has been great success with direct solar -> H2, needing, again, only sufficient demand for the hydrogen produced to be made industrially practical.
            • xyzzyz 6y ago
              Yes, it is conceivable that you could use cheap electricity from renewables, but it would have to be a lot cheaper than electricity from natural gas for it to make economic sense, probably something on the order of 5-6x cheaper. You get a factor of 3x just by using natural gas to heat directly, and then you need to account for bigger capital expenses for building plant and storage, because the cheap renewables are not available round the clock, so your production capacity must be significantly higher to produce more when they are available, to match the same average production of a standard natural gas plant, which can have smaller reactors etc but work around the clock. I think hitting 5-6x cheaper costs on average might be hard.
    • xyzzyz 6y ago
      If you generate the methane from biomass, and then burn it all without leaking any, I can’t see how it can be in any way worse for environment than biohydrogen.
    • smegger001 6y ago
      Not in the case of bio-gas, as it uses carbon already in the carbon cycle. If you pipe it out of the ground then yes.
• ncmncm 6y ago
  Hydrogen's high density of available energy per unit mass is the key to identifying where it is most potentially useful. Simply, it is by far the best of all possible aircraft fuels. Its one major disadvantage for this, as for most uses, is its low mass density: it needs more room than diesel to store enough to be useful. The tanks need to be bigger, and either strong enough to contain high pressure, or well-enough insulated to keep it liquid. Current aircraft store fuel in wing tanks not roomy enough for hydrogen. The most practical hydrogen-fueled aircraft would probably have a shape more like a lifting body than a submarine with skinny wings sticking out. So for best efficiency, we might need new airframes, but just using hydrogen yields major improvement. To oversimplify, the plane doesn't need to lift so much weight of fuel to cruising altitude, or carry it halfway across the world. Tankage has improved radically in recent years with the development of aerogels, which make practical carrying liquid hydrogen that need not held be at high pressure, so can be in tanks that conform to an aerodynamically-practical shape. (Other sophisticated storage methods increase weight, so are more practical on the ground.) Hydrogen is tricky to store for long or in large amounts, so the best way to use it is to produce it on demand where it is needed. A major airport would be a good place to produce it, as it could be piped directly into aircraft and used immediately. All the airport would need is water and power. Power can be collected by wind and solar over a wide area, delivered by transmission lines. The amount of water needed is negligible. Producing hydrogen would also yield plenty of oxygen, which might just be vented; but by carrying liquid oxygen, aircraft could fly higher, faster, and more efficiently, or at least get to cruising altitude more quickly. As electric power continues to get cheaper, uses for it such as liquifying oxygen along with hydrogen get more attractive. The first use will be in long-haul craft operating from a few major airports. It is possible that current large aircraft -- 747s, 777s, A380s -- could be converted, by using some of what is now cargo space for tankage, and replacing fuel pipes and pumps and, quite possibly, engines. It would be a big job, made attractive mainly by the extreme cost of qualifying new airframe designs. The lost cargo space would be made up easily by the much larger weight capacity, as tens of tons less weight of fuel is needed. Cargo aircraft today often fly half-empty so as not to exceed their takeoff weight limit.
  • nanomonkey 6y ago
    Pure oxygen can also be used in the pyrolysis phase of gasification, turning waste organic matter into syngas (Carbon monoxide and Hydrogen gas), as it produces a more pure fuel then using air alone (which is 60% inert nitrogen).