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Experiencing with Biogas in Arterra, Spain.

Producing our own energy from our kitchen waste.



  On April 2015 –and with the help of the Ecovillage Lakabe and Arterra Bizimodu–, I attended the seminar on biogas TH Culhane gave in Tamera, a RIE’s member community based in Portugal. With the knowledge gained there, a small entrepreneur Arterra group began planning the buitging of a prototype class digester IBC Solar Cities. The prototype was planning in June and was put into operation at the end of this month.




  To start building the prototype we had to buy or recycle a handful of parts:


- 1 container 1 m3 IBC

- 75 mm tube PVC

- 1 75 mm funnel for feeding mouth

- 1 T of 75 mm for the outlet

- 1 cubit of 75 mm

- 1 flight of 40 mm for gas leakage

- Tap

- Flat rubber gaskets

- Paint and accessories




  We build the prototype  following the instructions, painting it in black to help to absorb more heat. The temperature range in which the different bacterias inside the container have to work are key for the efficiency and success of the whole process. Then, the process of starting the digester began: a 1/1 mixture of cow manure and water was introduced, after introducing a couple of buckets of mud from the bottom of a nearby pond. By doing so, we help the starting process by adding  a number of inoculated bacteria already present in nature that help create a community of bacteria needed for the production of biogas. After, we worked on this initial culturing for two weeks without feeding, the time stipulated for the creation of that community.



  In two weeks, we had our first small disappointment. We had try to ignite the flame at the tap and test the digester, but in fact got to kindle, and when  removing the burner the flame got extinguished. And so on. The flame did not stand by itself, and still had an orange combustion. After persevering and  trying for two days and getting the same results, we decided to consult TH Culhane and his response encouraged us a lot: the system was not yet mature and still remained a small amount of oxygen in the digester that needed time to be consumed. We had to be more patient and wait a few more days.


  Feeding the digester after the first two weeks was gradual, from 5 liters of mix from our kitchen waste and water to 25 liters final. And four days later, ie about 24 days of initial culture we got our first blue flame, a proper methane flame!!! It only lasted a few seconds but each passing day the flame lasted a little longer, until 35 days after the start of the whole process we got a steady flame. We then bougth some material on Internet: an inflatable bag 1 m3 to store the gas, one adapted stove for biogas and a gas lamp. The material was not expensive, but  the transport and customs yes.


  With outside temperatures of between 20 and 42 degrees – and a constant waste supply – we managed to obtain a cubic meter of gas in about three days. The feeding of the biodigester came exclusively from organic waste from the kitchen, including cooked leftovers. Keep in mind that our kitchen produces about 30 daily services. After some  days, the period of time required for 1m3 of gas is reduced to 2 days, even in optimal conditions of temperature and assisted in feeding barley residues from the brewing process (with high energy) than another group performed in August and Arterra those días.


We then prepared our first coffee with our biogas supply and early September we made our first test in the kitchen. ! And it was a success! We got about two hours of cooking from 1m3 of biogas. In repeated tests it varied cooking time of 1.45 minutes to 2 hours. So we were able to cook for 31 people !!


  Today, 5 October, temperatures have fallen and so has made the production of biogas. Our challenge now is the winter and its low temperatures, so we isolate our digester (one straw bale construction and lime plaster) and perhaps also provide some extra heat source. We plan to build two more digesters to get enough stock to be able to completely replace the gas bottles we normally use. Q We hope our bacteria have not slept at all then.


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