What’s a Biodigestor? « Green Empowerment: the Blog

What’s a Biodigestor?

May 29, 2008 by annagarwood

The ultimate in closed-cycle resource use: The Biodigestor. You put cow manure in one end and get out usable cooking gas and organic fertilizer. The odorless gas is piped into the kitchen where it can be burned for 4-5hrs a day, replacing the need to collect firewood. The liquid fertilizer is rich in nutrients to boost crop production. And, the patio is no longer littered with cow manure. Biodigestors are relatively simple to construct and made with cheap local materials. It’s basically a huge plastic bag laying on top of straw, insulated between adobe walls and covered with a roof.

Last week a team of adventuresome students from the University of Portland came to Peru to visit the community Micro-hydro and Wind projects, and then get their hands dirty building a biodigestor with a local family…

Thanks UP for making it happen!

Posted in Peru, university partnership | 24 Comments

24 Responses

on June 16, 2008 at 3:03 pm | Reply Lisa Curtis

Wow that’s really impressive! I’m trying to make biodigesters in Kenya, any chance you could send your design my way?
on June 17, 2008 at 4:18 pm | Reply Anna

Hi Lisa,

Sure, I’ll go ahead and send you the designs…but they are in Spanish. You can also check out a group called IRRI in Mexico that are making similar biodigestors. Good luck and let us know how your project goes.

Anna
on July 8, 2008 at 1:46 am | Reply Rebecca Westbrook

Hi Anna! I am trying to build biodigestors in Honduras. Do you still have designs in Spanish? I would REALLY appreciate receiving a copy!

Thanks! Thanks! Thanks!

-Becky
on July 12, 2008 at 6:30 pm | Reply Santiago Giraldo

Hi. I would appreciate a copy of the design of the biodigestor. I would like to know, however, how difficult and costly would it be to build a biodigestor for a school scientific project?

Thanks.
on August 13, 2008 at 10:32 am | Reply Richard Johnson

This piece of kit sounds absolutely stonkingly good. There’s just one point I didn’t see in your article. This burns the methane I assume, a greenhouse gas 10 x more powerful than Carbon Dioxide. My chemistry is a bit rusty, but doesn’t this mean that you are removing one of the most harmful greenhouse gases from the environment, converting it into heat, light and less polluting gases.
on August 14, 2008 at 8:29 pm | Reply Anna

Yes, that is completely right. Biogas digestors destroy methane (which as you say is many times more harmful than CO2) usually released in decaying cow dung and at the same time displace the use of burning firewood which creates CO2. Some larger biogas digestor programs have been able to get emission offset credits because of this effect. Thanks for the good point!
Anna
on September 8, 2008 at 2:41 pm | Reply Ernesto Altahona

Great! could you please help me with the designs of the biodigestor! Im an student here in Colombia and It would be awesome if I could help the people in a town making one!
Thanks in advance.
(If you dont have the designs any information will be quite usefull)
on September 22, 2008 at 8:25 pm | Reply Tanguy

hola Anna !

Im building an eco bungalows project in Nicaragua in a remote place and the biodigestor is one of the most recomended in the area.
I understood that the gas is used for cooking but i heard also that it can be used with a “lombricultura”(in spanish, kind of bioworms) that reduce around 90% of the black water and an air pump… is your sistem use the same sistem?
Do you know the sistem Piraña used in Honduras, wich is also a biodigestor ? do you have any idea how to get those “worms”
could you send me copy of your disign to make me an idea, in spanish it s perfect.
Thank you
on December 1, 2008 at 8:42 pm | Reply Florence Reed

Could you direct me towards a well-known source of info on the chemistry of stopping methane from getting into the atmosphere by burning it? We occasionally get ask about this by donors when they see that we help people in Central America to build biodigestors and I would like a good article or quote from a reputable source to show them. Thanks.
on December 12, 2008 at 3:23 am | Reply Jess Gardner

Hi,
I am an Australian volunteer working in the northern Philippines. Ifugao, Luzon.
I am having trouble downloading the design and construction pdf. Could you email me a copy. We are very interested to build a small scale model here at the Ifugao College of Agriculture and Forestry.
Should we also contact the university of Philippines?
Thankyou in advance
Jess
on January 5, 2009 at 7:55 pm | Reply Amy Wagner

Anna,

I am volunteering with an organization in El Salvador and we recently went to Honduras to see a couple of different biodigestor models, one like the one that you mention, with plastic, the other a concrete underground structure. We’re having trouble finding the kind of plastic that they were using in Honduras. Any way that you could let me know what type of plastic you are using for the “bag”? If you have the design plans it would be interesting to compare them with the ones that we have as well.

Thanks,
Amy
on February 7, 2009 at 2:34 pm | Reply Open Source Hardware

Turn your design into a free, complete, published, and available Open Source Hardware design.

Just create another blog entry with the design including images and maybe links to free repositories, and append a link to that in this entry.
on February 10, 2009 at 9:14 pm | Reply Stefan

Anna,

I’ve seen biodigestors used with real toilets. Do you know if your design could be used that wya? We have a farm in Nicaragua and I want to improve the conditions for our workers. If we can use this to manage the waste water from toilets and burn the gas for cooking, that would be great! I’m not too worried about being able to get the fertilizer, but that would be a bonus.

Either way, I’d love a copy of your plans if you don’t mind sharing.

Thanks!
Stefan
on February 16, 2009 at 11:09 pm | Reply Anna

Hi Stephan,
Yes, there are designs of biodigestors connected to toilets, but the design we use would not be appropriate (I’ll email the designs we use). One consideration is that one has to be much more cautious about using human waste as a fertilizer. The “digestion” process would have to be longer than when animal waste is used, and I’ve heard that you’d have to be cautious using the fertilizer on vegetable cultivation. Another option would be composting toilets which would create fertilizer, but not gas.
Thanks,
Anna
on February 24, 2009 at 12:22 pm | Reply GlobeSon

Hi Anna,

Please guide me in designing a biogas digestor plant for a housing society in India.
The housing complex has septic tanks. The solid sewage is deposited in septic tank and the liquid effluent from septic tank is connected to the main sewage pipeline.
The housing complex has about 800 human residents (no cattle .

Please share any designs that you may have.

Regards,
GlobeSon
on April 14, 2009 at 6:07 pm | Reply Jesse Montes

Anna,
any chance you have these plans somewhere that i can access them? I would love to have a look. Also, have they been translated into English by any chance? Let me know, thanks!

Jesse
on May 21, 2009 at 2:41 am | Reply dogssleenue

Engaging information.. Will visit once more.
on June 24, 2009 at 5:49 pm | Reply barkinghorsefarm

Hi, we’re making a small-scale biodigestor here on our farm in Costa Rica. I was wondering if you could send us your design.
Thanks, Olivia
http://www.barkinghorsefarm.com
on September 21, 2009 at 5:36 am | Reply lindseyenterprises

would like to know how to and what is needed , I looked but could not find info on how to build small experimental sized
on October 13, 2009 at 2:28 pm | Reply Tim O'Hara

We recently built an underground, brick methane biodigestor at our place in Costa Rica (http://www.ranchomastatal.com). Anyone in the area’s welcome to come and take a peak. We use a combination of human waste and fresh cow manure. We’ve reduced our use of propane for cooking so far by about 40% (we cook for 20-30 people everyday three times a day). We’ve also installed 4 bag biodigestors in our community over the years. Great low-tech project for rural communities.
on October 29, 2009 at 4:34 am | Reply lindseyenterprises

Well, after 30 days and no reply ,I must have made a misteak , still trying to understand how to make a digester, One thing is making the bag , versus buying the bag, the other is why not use a water tank for horses and cows ,(live stock), as the tank instead of concrete, You see, I had a 10 feet diameter, round tank gave to me ,(metal)it is about 28 inches deep
on October 29, 2009 at 11:14 pm | Reply Anna

Hi,
We have not ever tried converting a livestock water tank, but it’s a good idea. Sorry I can’t provide technical guideance on it. Here’s a manual (in english) of a similar design to what we used. This is from AIDG Guatemala:

http://www.google.com/search?hl=en&rls=com.microsoft:*:IE-SearchBox&rlz=1I7TSHB_es&ei=2SDqSt-KBJ-ltgf43Lgw&sa=X&oi=spell&resnum=0&ct=result&cd=1&ved=0CAgQBSgA&q=manual+taiwan+biodigester&spell=1
on October 30, 2009 at 2:39 pm | Reply lindseyenterprises

Anna, tried to click on your link and it just takes me to GOOGLE SEARCHnot the manual, tried to cut and paste , would not work either, tried to type all the link in ,still not able to get manual.
on October 30, 2009 at 2:51 pm | Reply Anna

You can download the manual by clicking “Biodigester Installation Manual” (the second link) from that Google page, or alternately, directly from the AIDG site:

http://www.aidg.net/index.php?option=com_remository&Itemid=34&func=fileinfo&parent=category&filecatid=14