Making your own natural gas

A guest post by Robert P

[This is an entry in our non-fiction writing contest where you could win - First Prize a 10 Person Deluxe Family Survival Kit,  Second Prize an Herb Seed Bank or Third Prize a copy of Dirt Cheap Survival Retreat.  For complete rules and list of prizes see this post.]

I have learned a lot from this website from food storage, gardening and a prepping in general. One of the main concerns for all of us who are prepping is the energy we will need to survive if things ever get out of hand.

I see most of the information posted dealing with either the storing of petroleum products we can’t replace or solar energy. Do not take this the wrong way these are great alternatives and should be looked into and done, solar energy can provide years of reliable electricity to help fuel our way of life but most on this website feel that natural gas is something we cannot make ourselves.

I would like to argue that point because it can be done from just a couple cubic feet per day to thousands of cubic feet per day if you have the resources and the time.

I will say that most of us are capable of producing 20 or 30 cubic feet per day. This is not enough to heat your home and the modifications necessary to do that is probably beyond what most of us can do or should do. But we can use the fuel to supplement the fuel we have stored away for cooking, and water purification.

The process I am talking about is anaerobic digestion of plant and animal waste (manure not animal pieces and parts) this is a well understood science that is used around the world and is one that the homesteader can use for a very small investment.

I know you see anaerobic and everyone shies away from it thinking that they are a bad thing, in your compost pile it is. In a controlled environment they are actually a very useful bug. Anaerobic digestion of decomposing plant and animal waste has three main byproducts carbon dioxide and methane plus a very good fertilizer when it is all said and done.

There are two main types of digesters plug or continues feed digesters and batch type digesters. The plug type you add material on a regular basis while removing the same amount. With the batch type digester you fill it to begin with and let it do its thing once its done you empty and start over.

The plug flow digester is a larger system designed for people with multiple cattle and such who have a steady supply of organic matter, they are also a little more complicated to run and design. The batch type digesters are very easy to build and maintain require attention only when emptying and filling the digesters so I will concentrate on the batch as it is the one I feel most of us can benefit from.

A few quick pointers about bio gas and bio gas digestion

1. You are making a gas that is 50% methane and 50% carbon dioxide. Methane gas in the right concentrations is highly explosive unless you want to be on the 6:00 o’clock news because your house blew up be extremely careful with this stuff. What you are making can and will kill you if you do not take the necessary precautions. don’t get me wrong this system can be very safe and affective but when you work with it double-check everything and never store any of this in a house or other enclosed area.

2. You can use any plant matter for the digester and animal manure, never use animal carcasses, flesh bone and blood. The anaerobic bacteria turn this into hydrogen sulfide a flammable gas with a very objectionable odor smells like rotten eggs, it may or not be dangerous as well but it is to be avoided . The anaerobic bacteria need a carbon to nitrogen ratio of roughly 30-1 so a great way to get rid of the falls leaves that are in the yard.

3. The anaerobic bacteria are found in nature when you seal the container but you can speed up the process by adding a couple shovels full off fresh cow manure or by using a seed from a digester you are cleaning out.

4. The process requires a temperature range of 59 to 122 degrees but they do best at the higher end close to 100 is normally good. They do not like major fluctuations in temperature so insulation will normally be required. I have some ideas about this to be included later.

The basic batch type plant is very simple to construct with common everyday items. For the digesters I would use plastic 55 gallon drums that the whole top comes off. To the lid of these you want to put a pipe connector this is where the gas will leave the digester and go to your storage tank.

To this you want to have the gas pass through a water trap to make sure that if the gas catches fire it cannot reach the digester. The gas is then piped into a gas storage tank which is simply a 55 gallon drum with no top on it filled with water then you have a smaller drum with no top on it put inside the 55 gallon drum upside down so when the gas leaves the pipe it is caught in the upside down drum.

You place stone bricks what have you on top of the smaller drum so that it can hold more gas by pressurizing the gas slightly. Another gas line is connected to the smaller drum in what would be the bottom but is now the top, this is piped through another water trap then on to your point of use, propane grill or Coleman burner would be my suggestion.

This gas is 50% methane and 50% carbon dioxide and it isn’t truly natural gas as it has about half the energy of natural gas at 500 BTU per cubic foot it is called power gas. You can technically use it to heat and cook in your home but ports and burners need to be changed out to do this and I am not sure how all of that works I would do some serious research before I tried it.

On average the digesters should produce roughly 7 cubic feet of gas per day as it generally produces the same amount as the size of the digester. So each digester of this size should produce 3500 BTU of gas per day, there are a lot of variables in this however. The temperature is the largest of these followed by the feedstock. With just a couple of these you should easily be able to boil water cook a meal and such.

To fill the digester you want to crush, shred the feedstock as much as possible as the bacteria feed off the edges of the material this will make it produce gas much faster but for a shorter period of time. Fill the drum with your feedstock as tightly as you can to about 3 inches below the top of the barrel fill with water and put the cap on. If you have access to fresh cattle manure a scoop of that would speed up the start-up time as the high volume of anaerobic bacteria in cattle manure.

When the digester is sealed the first couple of days up to a week the digester will provide mainly carbon dioxide until the oxygen is consumed inside the digester.

When the digester is finished it will no longer be producing gas there for no bubbles in the water trap. It is time to clean out the digester and start over. The easiest way is to use a five gallon bucket and dip out as much material as possible this can be used directly in the garden and is a very good fertilizer.

When you can’t dip out anymore of the material simply pour the rest into buckets as it will now be far lighter. You may want to save a small bucket or 2 litter bottle of the affluent sealed and kept out of the light as a seed for the next batch.

To keep the digester warm and a stable temperature I would suggest covering it in compost as the heat from the composting will heat the digester while keeping it insulated from temperature fluctuations due to changing temps during the night and week to week.

There is no limit to the number of digesters you can connect other than availability of feedstock.

At this scale this is not the answer to all of your energy needs but it should be able to fill at least a portion of your energy needs. Digesters started in late spring or early summer should be coming on-line real well to help in the canning season. Allowing you to save your wood and other stored fuels to keep you warm in the coming winter which is critical. This may not be a total energy system but it is another feather in your cap to help when it counts.

There are a lot of resources for this on the web I invite you to look into them. Ram bux singh is considered a pioneer in the field and ran a huge system in India, just google anaerobic digestion, and bio gas and you will find a wealth of information. I hope I have provided a basic understanding of the system and opened up a few eyes to another energy system. Good luck, god bless and happy prepping.

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  1. OK, I think I get it, it’s like brewing your own hooch. The compost/poo ferments, makes gas, you put the gas through an airlock catch the gas in something like an air lock-tank thing, when it’s done fermenting it’s ready for the garden and you have fuel too. I guess it would be like capturing the carbon dioxide from brewing as well as the alcohol.

    One thing I didn’t understand is, the small barrel that is upside down inside the larger barrel, is that full of air or water to begin with? If air, you’d have to weight it down to keep it from floating so I’m thinking maybe water – but just let us know. Thanks.

    • I built some of these systems to play with back in my youth, and although they do take a little effort to construct, run and maintain, they could be well worth the effort in a post collapse scenario. I would add a small relief valve on the top (original bottom) of the small barrel. When you set it upside down in the larger barrel full of water, it will be full of air and float. Opening the relief valve will allow air to escape and allow the barrel to sink. When the small barrel is filled with water, close the valve. Incoming bio gas will now replace the water and you will see the barrel rise as it fills. It essentially works as a low pressure storage tank with a built in fuel gauge.

  2. Matt in Oklahoma says:

    Robert P
    Interesting article, I try alot of the things I see posted rather than just reading and believing, it has shown me some real mixed results in the solar fields so knowing that I have a few questions before I attempt this experiment if you have a moment:
    What safety precautions are needed, what are the dangers? That was a little vague, if I was to read this then go out and practice it what exactly do I need?
    Also compared to cutting heating wood or collecting deadfall and dried manure for working (not cooking) heat how does this rate in time consumption comparisions?
    How do you bottle it or is it just for direct use from the smaller barrel to the stove?

    • robert in mid michigan says:

      ok went to school for this back in the early 90′s unfortunatly the school go tclosed for to many studants on the books and not enough in the classroom. so i did not get my degree but like ohio prepper said it is a lot like fermenting beer, and was probably responsible for the field as beer was left in a closed container the gas burned.

      the safety requirements are pretty simple its called a water trap in the lines i have seen two and a half gallon jugs used for the water trap with the water jug filled three quarters of the way with water, two holes drilled in the cap one has the hose from the digester run through it and the end is below the water line so that the gas bubbles up through the water and the other line does not go below the water and is run to the holding tank make sure that the cap is leak proof using silicone or something this means that if you get a fire it cannot make it to the holding tank or the digester. its simple and effective the container doesnt matter on the size but you want it large enough that the hoses can fit into it and you want a couple inches of water above the gas in hose. hope that helps i have drawings of it but cant figure out how to get them online?

      wood is a better fuel in most cases, but this uses a fuel source you normally would not use allowing you to save the wood for heating or cooking when this fuel isnt realy available middle of winter and everything is frozen. it also allows you to use the compost for fertalizer still where when you burn wood it doesnt add much to the garden. as a side benafit when you burn natural gas thier is no smoke, can easily conceal the light from the flame and is also instant on and off helping with opsec in a bad situation.

      time to set up the system isnt to bad proabably could be done in a few hours and after that when changing out the digesters and reloading you are looking at a couple hours each.

      thier are no easy ways to bottle or store the gas long term at this scale, you could build more storage tanks to hold larger amounts but as your compression will be low the amount of space needed to store any real energy would be astranomical.

      the great thing about this is that it is completly scalable to any level you want or have the materials for. thier is a dairy a couple miles from here who use it for thier 5,000 head of cattle and they are getting well over 50,000 cubic feet per day and the manure is ready to be put into the field as soon as it is finished no waiting and aging. a plug flow for a post shtf scenario where you have a comunity to supply the material and use the gas for central heating or larger scale electrical system would be the best system but on the homefront a weeks worth of gas would allow you to run a preasure canner with several digesters going you may be able to do a batch per night saving wood and other fuels.

      • Tom the Tinker says:

        I have watched videos of Asians and South Americans transporting bio gas using everything from truck inner tubes to large plastic tubes and bags. Risky for sure with the plastic bags and such.

        I saw a set up in 08 on a link showing a couple that used a batch system with a dual inline water traps using a truck tire innertube. digester to filter to a T valve that kept the innertube ‘charged’ (not very charged) from the other side of the T valve they ran the gas into the shed kitchen via another tube to a second water trap in a jug then to the counter top and their two burner ‘stove’. It allowed them to ‘charge’ the innertube, close the valve to the digester, and open the one to the stove when they used the gas. They used a half sheet of plywood on top of the innertube and a cinder block to ‘pressurise’ the system when they wanted to cook. The digester was vented to the air at the time cause they produced all the gas they needed for the two of them to cook with using that one jumbo innertube. I know… cue the banjo music… it worked. What are you supposed to say now…. Idonno… it worked. So do a lot of cludge bio gas and wood gas ‘generators’. Thank You Robert P.

        Question for Robert P or anybody else…. does this type of gas ‘store’ well or decay in some way?

        • robert in mid michigan says:

          its natural gas and if you can keep it sealed will store extremly well but innertubes and such will allow gas to escape overtime but it willnot decay same as propane that way.

  3. There is a much easier way to make natural gas–just have a generous portion of beans and rice.

  4. Hi, only had time to read quickly, so will go over with more detail later.

    Look for articles, pdf and videos of the Jean Pain Method, he was from France, you will be impressed, bio fuel and bio heat. Just to add to your article and not take away from, positive info.
    Thanks I liked the post

    • robert in mid michigan says:

      same system i described with a tank heated with compost he uses a much larger tank than i suggested. i made my suggestion around things that are conveniantly located all around us if you could get ahold of a 5000 gallon tank and are willing to do the work you could do a lot with that at 8 gallons per cubic foot that would be roughly 600 cubic foot of gas per day with about 300,000 btu per day.

      definatly look into his system it is a good system i just dont like the innertube storage for gas because they get damaged over time then you have a gas leak if you are not on top of can be dangerous.

      thier are a lot of sites out their with all of them using the same basic system with differant ways to heat, store the gas what not and what may be the golden bullet for you that makes this system work for you may not work for some one else so please look into them study them and agust as you can. i look at this as another arrow in the quiver for a shtf scanario.

  5. muddy fork says:

    These systems have been used in India, Philippines and other countries for years. They build large dome shaped or rubber balloon topped digesters and use the gas to cook with every day. A Google or YouTube search for bio-gas will result in some interesting reading and numerous how to build guides. If I was in a position to live off my farm and not have a “real” job I would build one in a heartbeat.

    • robert in mid michigan says:

      thier is a great book on a guy in south africa who ran his farm on one for years. the nice thing about this book was that it covered the problems he encountered over the years and what he did to correct the problems. i will look in my books see if i cant find the title but i do know its out of print has been for twenty years plus but some libraries may have it. ill get back on this.

      • Mother Earth News Handbook of Homemade Power.

        Out of print, and I don’t have a copy.

        I forget how many pigs on the farm, but it ran a 6 horse engine tied to a generator.

        • robert in mid michigan says:

          thx could very well be the book most of mine are far more technical in nature measuring volitile solids and methane to co2 ratios

  6. This is the kind of project that would have to be “farm sized” to produce any real output. I note that my furnace puts out 26,000 BTU’s per hour. It takes 7.43 x 3500 btu per hour to run. The furnace does not run all the time – maybe 4 or 5 hours total, in short bursts a day.
    So, I’ll need 30 (7.43×4=29.72 rounded up) to 38 (7.43×5=37.15 rounded up) 55 gal. barrels brewing in my backyard with enough storage for 133,000 btu a day for a Michigan winter. Then, there is the job of cleaning out and refilling the 30 to 38 barrels – each week.
    Solar hot air (see the solar project article, lower right corner of the roof panel picture) is less work (no shoveling sunlight) and makes a great “supplement” to a wood stove.

    If I want to cook a meal, a small rocket stove (or wood gas stove) and (gathered) sticks would save me from having to shovel pounds of stuff into (and then out of) a barrel.

    • michael c,
      I’m not really doubting you, but is your furnace really only 26,000 BTU? Mine is 97% efficient and is 80,000 BTUs. The calculations actually recommended a 100,000 unit, but insulation and new windows allowed me to go with the smaller unit. I’m just wondering, since I suspect your Michigan winters are consistently harsher than mine here in central Ohio.
      If it really is 26K, do you have other supplemental heat, or some other tricks you’re using to use the small furnace, and obviously use less fuel? This is intriguing and may offer some of us a money and fuel saving option. Since I keep a fairly large quantity of propane here, it would not only save money in the long run, but also help me stretch a fuel supply for a longer period if there are interruptions or shortages.

      • It is the (small) furnace for my trailer (64×13=832 sq.ft.) but, even if it were bigger then I would need even more “gas” to run it. (In the really cold days it might run 7 hours for the day) There is a fireplace that right now is not used.

    • robert in mid michigan says:

      solar hot air is probably the best alternative energy for an individual/ family on a cost to benafit ratio now or in a shtf scenario of that thier is little doubt but my knowledge on that field is limited. yes to heat our homes or make a huge amount of gas is impractical for most people but that doesnt mean you should not learn about other ways to make energy.

      i look at it like learning to forage for food i do not like dandalian leaves but i know how to collect, prepare and that they are edible so if i ever have to i can use them. just another arrow in the quiver

  7. SrvivlSally says:

    Constructing the entire setup sounds easy to do and it would be interesting to see the output results after tripling or quadrupling the mentioned size. Thank you for adding another helpful article, Robert P.

  8. robert in mid michigan says:

    believe it or not this system has been in use around the world for over a hundred years and normally in third world countries because access to natural gas was very limited they found ways around the problem.

  9. Another good source on making natural gas is from an old tv show “Green Mechanics”, they made a larger tank for the manure and a bigger tank for methane. The episode is great for making natural gas, but also for converting a gas powered riding lawnmower to methane powered lawnmower.

    • eric,
      I think I remember that show, but not that episode; however, with multiple ways to heat a house that are easier, I think that running an engine, like that of a generator could be very useful.
      There are also ways to scrub the CO2 from the gas to make it more efficient, but these mechanisms may be a bit complex for the homestead digester. Might be worth looking at.

  10. I produce all kinds of natural gas …………… just dont know how to harness it for power just yet .

  11. Wow I thought I was going to be first to post a juvenile comment about making my own natural gas, but was beat out by several people. That’s what I call a like minded community.

    On a serious not I don’t think I will have the resources to complete this project but way to go on getting us to think about the energy subject.

  12. Tom the Tinker says:

    MD this was another good post. My printer is turning out a nice series of entrys for my binder ala the links and refs from today. Thanks again everybody……………. Does anyone else in here see a growing market for quality… used…. plastic barrels?

  13. Not related, but Staples holds sales all the time for Laser Printers that are as low as $50, much better and cheaper than ink jets for similar pricing.

    To print up your binders

  14. TexasScout says:

    The average “Coleman stove” burner is 8-10,000 btu. Do the math.

    • robert in mid michigan says:

      per hour? dont own one so just asking.

      lets say an hour then two of these would give you one hour of cooking per day for roughly 60days, enough time toprepare a meal not a perfect answer to all problems but an alternative.

  15. As a side note be careful of using pig feces. Anaerobic decoposition of pig feces can and usually will result in the release of H2S or Hydrogen Sulfide gas. H2S is very dangerous as it is deadly in concentrations of as little as 100ppm and while it has a very foul smell it also causes the ability to smell it to be lost in concentrations of 10ppm-20ppm so long before it’s deadly you loose the ability to smell it. At the higher concentrations it acts as a nerve agent because it shuts down the nerve signals from you brain to your heart, lungs and limbs, ect.

    I work around H2S and I recommend that anyone thinking of building one of these look at taking an H2S course and consider getting a gas monitor to detect it. Also I’d avoid putting the digester into a building since a leak can build up quickly.

  16. It’s called Case Grande Resturant’s Pan Filo Burritto I make enough gas in one night to power 3 aircraft carrier’s and a dingy for 6 month’s.
    I could solve America’s energy Crisis but it might get the current President re-elected.

  17. MustangGal says:

    Heifer International also has some intesting information on biogas.