Many independent variables govern the performance of anaerobic digesters. Temperature, nutrients level, loadings, mixing, SRT, LRT, and solids recycle impact the performance of the digesters and the gas production.

Low bacterial population leads to low waste stabilization, resulting in low gas production. It is not only the question of rate of gas production, but also the percentage of methane component of the gas. Typically, 50 per cent of the methane component in the gas signifies essentially carbohydrate nature of waste.

Batch mode and continuous operation mode entails changes in the volatile acids concentration (their production by the acid-formers and, utilization by the methane-formers) and, this in turn, impact the gas production. Continuous operation of digesters, after reaching the equilibrium state, in general, give stable performance, assuming there are no wide variations in input variables.

F H Mughal

Good idea.

We have the methodologies ready to measure lipases, cellulases and proteases.

We will try it.

For those of you interested in Toni's research, I can recommend watching this online discussion that we recorded with Toni on 1 July.
Toni's presentation starts at 2:32 into the recording (see attached file below); it is followed by questions and answers that start at 10:13 until 14:20.

I have added the Youtube link below to start at exactly the right time:



In the question session, the following was discussed:

• the role of the stabilisers (they prevent agglomeration of the iron nanoparticles) in the observed increased biogas production; as well as the possibility that enyzmatic activities are increased with the additional iron.
• I asked Toni a question about the costs: he explained that iron nanoparticles are very cheap when they are industrial grade (but expensive in the lab because here it is high grade). So he thinks that costs for adding the iron oxide nanoparticles should not be a prohibitive factor, and that the increase in biogas production (up to 70% increase in the lab) should far outweigh the additional costs of the nanoparticles.

Thank you, Toni, for your participation in this!

Hi Toni

I was wondering if you are still continuing with this projects as you had mentioned in the webinar we back in July?

Did you find out why the iron nano particles actually resulted in 70% biogas production increase (I am not sure if it was that much, in the figure you shared fin June it looks to be a little bit less but still a lot…) and why some of the particles prepared with different stabilizer didn't show that effect at all?

Did you manage to reproduce the biogas production increase also in pilot scale (100L) and continuous mode? You mentioned you were looking for a fecal sludge treatment plant in spain to test this if possible?

Cheers and happy new year,
Dorothee

PS: Has the paper you mentioned here been accepted, would it be possible to share it or a version of it?

Links, further readings, etc:
We are in the final stage of submitting our main first results to the journal "Science". Of course, the paper includes the funding of Gates Foundation in the acknowledgements. However, the paper is still in the hands of English revisers. I would prefer to include a link when the paper is published (in Science or other journal).

Yes, we have very positive results.

However, we are about to publish it, and they are not still open and validated.

I will put the links here when the acceptation arrives (let's hope so!).


Toni

About batch processes:

onlinelibrary.wiley.com/doi/10.1002/smll.201303703/abstract

Now working in a paper on continous mode.