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Energy from Weeds

Discussion in 'Off Grid Living' started by Ganado, Apr 27, 2016.

  1. Ganado

    Ganado Monkey+++

    Is this realistic? I was searching LadyBug feeders and found this. Perhaps some of our techinical experts could chime in?
    Make Energy From Weeds - All

    The link above has the entire article. Below is his comparison to LPG
    Liquefied Petroleum Gas (LPG) versus Biogas

    Another test to find out the actual efficiency of the biogas is to compare with Liquefied Petroleum Gas (LPG) normally used in our household.

    In our home, a full LPG cylinder containing nearly 15 kilograms of gas normally lasts for about 30 days. So, our consumption works out to about 500 grams of LPG per day.

    As you can see in the pictures above, I have placed both the systems (one using LPG and another with Biogas) side by side. On 13 October 2014 we installed a new LPG Cylinder and started using both LPG and Biogas simultaneously. The LPG cylinder was fully emptied on 24 November 2014 and replaced with a new one.

    The LPG cylinder which normally lasts for only 30 days has now been utilized for 41 days in conjunction with Biogas. At the rate of 500 grams of LPG per day, the additional 11 days X 500 grams = 5500 grams of equivalent LPG has been supplemented by Biogas.

    Production of Biogas per day from weeds equivalent to LPG = 5500 grams /41 days = 134.15 grams

    So, 0.226 cubic meter of biogas produced everyday ( mixed with Carbon Dioxide, Nitrogen and Hydrogen Sulfide), gave us 134.15 grams of equivalent calorific value of energy in comparison to LPG.
    arleigh, Aeason and chelloveck like this.
  2. ghrit

    ghrit Ambulatory anachronism Administrator Founding Member

    Realistic? Yes. Practical? Different question entirely. What I did not get from that write up was whether they were mixing the digester gas with the LPG. That's risky business by itself. Using the different gases in different applications is safe. I'd want to look at the numbers a bit more carefully, too.
    kellory and chelloveck like this.
  3. azrancher

    azrancher Monkey +++

    They were talking many years ago about raising tumble weeds for wood pellets, I think it could be workable.

  4. Ganado

    Ganado Monkey+++

    What I posted are the results of his comparison of LPG and weed Gas running side by side to see which ran longer.
  5. ghrit

    ghrit Ambulatory anachronism Administrator Founding Member

    Hm. That's not the takeaway I got. Using both made the LPG last 33% or so longer if I read it right. In other words, supplementing the LPG with digester gas (hopefully in separate burners) stretched the time between LPG bottle replacements. That, I can easily believe. (But I've been wrong and caught off base before ---)

    "Normal" digester gas is about 60% methane, the rest mostly CO2 with a few percent of other stinkers. LPG is the usual designation for propane, not nat gas. They are NOT the same thing, just closely related. Of the three, propane has the higher heat (BTU) content, commercial nat gas next, and distantly followed by digester gas. The equipment used to burn all three are essentially identical in form but different in air/gas mixing ratios. This must be watched carefully; using the "right" burner with the "wrong" gas will give at the very best unsatisfactory results, and in the worst case, disastrous results.

    Commercially, digester gas can be a very economical way of saving money. However, it works economically only where there is a cheap source of feedstock for the digesters. You'll see a lot of that sort of thing at sewage treatment plants, and there have been some semi experimental digester installations at dairy and beef farming operations. The methane is used for process heating, and where the plants are large enough, for power generation. (Now, don't be confused trying to differentiate plant waste with animal wastes, the same process of anerobic "digestion" (scientifically speaking) is identical.) Economic quantities of methane is the goal. BTW, grinding the plants is better done by the animals than a mortar and pestle from the standpoint of economics; it takes one step or more out of the feedstock preparation process. In truth, grinding is NOT required, but then you have to add a LOT of extra time for the plant waste to break down and a much larger digester would be needed.
    arleigh, Aeason, Ganado and 2 others like this.
  6. UncleMorgan

    UncleMorgan I eat vegetables. My friends are not vegetables.

    For someone who wants to try biogas production on a small scale at low cost, without committing to a lot of concrete work, I recommend:
    as a a possible starting point.

    But I'd use plastic barrels rather than steel. The kind with ring lids. (Pic attached.)

    Note that the Biogas plans call for 2cm fittings and lines right up to the point where the system narrows down to the diameter of a tire valve (less core). That 8mm bottleneck means you'll never get gas out at a rate faster than you would if you were just using 5/16" tubing everywhere. So you might as well just go with small tubing and hardware throughout.

    The pressure fittings are screw-in truck tire valves, less core. Two tire valves soldered back to back on the purge line allow easy attachment of the weighted hose.

    The gas lines from the barrel and inner tube have valves and meet at a tee. The third line from the tee is also valved and runs to the burner with an in-line flash arrester--the kind you can get at any welding supply store.

    With a flash arrester you wouldn't have to worry about a little air in the line. Sure--purge all the air out of the system to start, just like the booklet says. But remember that methane is lighter than air, so in a slow flow line there won't be much mingling, and in the tube and the barrel, any small amount of air inside will stay on the bottom like water in a carburetor bowl.

    If any air does make it up to the burner, you'll get at most a small pop or flare in the flame, and then go right on cooking.

    Put another fitting in the lid with a weighted hose that drops down to the normal full-liquid level. That's the purge line, and it can also be a coreless tire valve with a cap.

    Obviously, all the hoses should be clamped gas-tight.

    Each time you need to open the barrel, purge the air out of it after you close it back up. To do that, just open the line to the inner tube and the purge valve at the same time.

    The methane in the inner tube will flow into the air-filled barrel and push the air inside right out the purge line, along with any excess liquid. After a short while, only methane will be coming out. When the output starts smelling skunky, yer done.

    Don't forget to push a temporary drain hose over the purge fitting to direct any excess liquids into a handy bucket.

    When purging is complete, cap off the purge fitting and you're back in biz.

    The advantage to using completely unmodified plastic barrels is that you can take off the ring and lid, substitute a newly filled barrel, and haul the expended barrel off to the garden to spread the fertilizer at your leisure. The advantage of using three valves is that you can disconnect anything without a lot of purging after it's all put back together. And you can also purge the barrel slowly.

    I didn't draw one in, but a small pressure gauge on the storage line wouldn't be a bad idea. It would, at the least, let you record the changes in the gassification cycle, and let you know about how much gas you burn per hour on the stove.

    Last edited: Apr 27, 2016
  7. Ganado

    Ganado Monkey+++

    Thanks Guys! I don't have the skill set to see if that was realistic or not. Really appreciate the time you took to answer that question[biggrouphug]
  8. UncleMorgan

    UncleMorgan I eat vegetables. My friends are not vegetables.

    Oh--one other thing: When making bio-gas, chopping the bio-mass up fine is important. Mulching it into a mean green (or brown) smoothie is the ideal pre-treatment. But most people don't have the machinery for that or the budget to buy something that will fragmentize things on a truly fundamental scale.

    Check this out:
    How to Make a Papercrete Mixer - Mike and Molly's House

    Papercrete is great, but in addition to that, the mulching/mixer trailer from this link would be perfect for liquefying your bio-mass materials, including all forms of plantlife, and/or animal dung.

    It's a fast, cheap,& easy solution to what is probably the hardest part of producing your own biogas--making up the slurry.
    Witch Doctor 01, Aeason and Ganado like this.
  9. arleigh

    arleigh Goophy monkey

    Adding manure, I'm told, makes a more efficient use of the process.
    They have been doing they in Europe a very long time. and even in china and japan they have made community digesters for gas .it's not that complicated .
    Ganado likes this.
  10. Ganado

    Ganado Monkey+++

    Thanks @arleigh can you say more? I was actually asking if the device would work. It seemed very simple and I like simple
  11. arleigh

    arleigh Goophy monkey

    I have been setting aside materials for this project a long time.
    Way too many irons in the fire , but there always will be, right ?.
    An engineer friend of mine told me that methane gas is among the hottest fuels there are and some what unstable/ inconsistent .
    Most of the experiments have boiled down to mixing gas to temper the heat a bit ,so it makes good sense to blend the two; propane and methane, if you plan on using them in an engine ,say a generator.
    Methane is so hot that usually special valves (Engine intake and exhaust valves) are required for that fuel , stellite I believe.
    As for burning in stoves and heaters it's not that critical , but like any fuel, the oxygen mix is important for a the cleanest burn you can achieve.
    One of the reasons I have held off on methane, is learning about making alcohol, which is adding heat to the digester and recovering the distillation, which is far easier to store, and to dispense, and more compatible with various forms of use, and less volatile .
    East Asian schools make alcohol for the kids to have lamps to study at night with after school .
    They distil the garbage from the school on site. the lamps are a simple tin with a wick.
    I have an alcohol stove for a sail boat to use if/when I get this going .
    Having solar for the water heating, and wood stove for cooking an heating, I really only need gas for generators and working metals, and that only if/when I run out of coal.
  12. ghrit

    ghrit Ambulatory anachronism Administrator Founding Member

    I am not too sure what your engineer friend meant by calling methane a "hot" fuel. Methane is exactly and nothing more than natural gas, and requires no more special attention than is given to water heaters. It is highly stable, and there is no need to mix it with anything to improve its fuel characteristic. Mixing it, especially with propane is NOT a good idea, since the mix would need precise control to make for safe burning. Commercial natural gas is controlled to pretty exacting standards which in fact are very close to what occurs in nature (i.e., at natural gas well heads.)

    Gasoline and diesel fuels actually have higher energy density and (under equivalent conditions) higher flame temps.

    I suspect you may have crossed up between methane and methanol.
    BTPost likes this.
  13. arleigh

    arleigh Goophy monkey

    Thank you very much for the correction ,I needed that. you are right .
    I guess some times even engineers make mistakes .
    I should have looked it up first , still getting use to this computer age.
    No excuse.
  14. ghrit

    ghrit Ambulatory anachronism Administrator Founding Member

    Yes, we do --- :lol:
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