A blog from University of Borås

Sunday, February 9, 2014

Why big digesters for biogas? A PhD thesis

If you have seen biogas processes, you have probably noticed very big vessels for the biogas productions. They are normally 100-10,000 m3 in size. The reason of this big size is that the materials should stay in the reactors for about 30 days. The bugs that do the job and produce biogas are sensitive and need long time to grow. Just as example, you can compare E. coli bacteria that can duplicate itself in 20 minutes, while a methane producing bacteria (or archaea) need about 2 weeks to duplicate. It means if you don't want them to get away from the reactor, you should have big vessels, feed it slowly and let them to stay longer than two weeks.

In a PhD thesis that will be defended 27 Feb. 2014, Solmaz Aslanzadeh found a method to reduce this retention time from about 30 days to about 6 days! It means if her results can be applied commercially, the biogas digesters will squeeze by 80% in their size. You can read her thesis to see how she did it:

Thesis title: Pretreatment of cellulosic waste and high rate biogas production


  1. Dear Prof Taherzade,
    Thats awesome, honestly once saw the post on FB and read that I was really interested
    I had a look at the abstract and just I am wondering the energy economy of mixing that such big reactor, isn't it?

  2. The energy consumption of the process almost similar to the traditional ones, but we haven't checked exactly if it is reduced to increased. The main point is the reduction in the investment,

  3. Also decreasing the incubation time from 1 month to 6 days considering a great job!!! less days, less energy consumption for maintenance of reactor by 80% comparison with conventional procedure (30days) isnt it?

  4. i hope it will be an amazing invention, Solmaz, as a friend of you i'll support you with prayer from indonesia, good luck

  5. i hope it will be an amazing invention. Solmaz, as a friend of you i'll support you wiyh prayer from indonesia, good luck