From cow poop to shaft power!

Biogas from a small digester I built runs my Stirling engine fan very well! You can see the beautiful blue flame, untreated biogas direct from the gas holder burning cleanly and very hot. The weights on the inverted 5-gallon bucket provide increased gas pressure for the burner.

The potential applications for a small biogas/Stirling engine system are endless, and the built-in advantages of simplicity, sustainability, and low cost are hard to beat. I used cow poop to feed this digester but many other wastes could be used. Hope this is inspiring for other engine builders!

Category:

Science & Technology

Tags:

• Stirling
• engine
• hot
• air
• motor
• fan
• biogas
• digester
• gas
• holder
• at
• appropriate
• technology
• sustainable
• development
• eco
• green
• casero
• home-built
• diy

[BocajBinLadin]

to make a biogas maker couldnt i just put manure in a bucket put a top on it and run a tube from a hole in the lid to a burner? wouldnt that work?

[approtechie]

@BocajBinLadin Not quite. You need a way to collect the gas so you have enough to burn for a while. You also have to make sure all the oxygen is out of the system before you light the gas so the flame doesn't go back the tube and make a big mess! Usually the first batch of gas collected is exhausted to the atmosphere without burning it.

[llonnette]

1:45 *i looked somewhere else*

1:46 *bum* what?! engine fails?!

oh.. *disatisfied faces*

lol jk, that was a great thinking rly, i imagine it in industrial scale

[approtechie]

@llonnette lol!

[swordjojo]

a fan to make cow poop smell go way =D

[approtechie]

@Mhall815 I wish I had more time to mentor you on building a more useful engine but I'm pretty much up to my ears now with what I already have. I put some photos of my engine at the end of my video "Beta Water Bottle Stirling Engine" that might give you some ideas how to build a more powerful one.

[Mhall815]

@approtechie Thank you for the useful info. The thing is that Im doing a 100p project on stirling engines and am thinking about doing some practicall work. Im almost done doing a small beta type coke can engine and am thinking about doing something a little bit more challenging since I have 140 h of project time. Do you have any suggestions what I can do? I got a home workshop to my disposal with a substantial amount of tools and possiblillity to borrow some more.

[approtechie]

@yellowmetalcyborg The bacteria are in the environment pretty much all around the world but take a while to get going. Adding some animal droppings to the mix really accelerates the process since the bacteria are found in large numbers in the gut.

[yellowmetalcyborg]

@approtechie Thanks for the info. I'm a high school student, so I don't have access to a lab. A bunsen burner is a starting point. It allows you to melt glass and to perform certain reactions that require high temperatures, the rest builds off of that. I could just buy propane and butane, but where's the fun in that :)

Also, what kind of bacteria should I put in the digester? should I throw in some cow stool so as to ensure that the right bacteria populations are in the tank?

[approtechie]

@yellowmetalcyborg If you Google "biogas feedstock" you'll get a lot of info on the various types of material useful for producing biogas. Lipids (animal fats) produce high quantities but you have to provide sufficient N along with it and keep the pH between 6.8 and 8. Several large companies are successfully producing biogas from their animal processing wastes. Temperature needs to be kept at around your body temp (your gut has similar bacteria in it) for mesophilic bacteria to thrive.