Digester Feeding

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RAROSUE AMARAIBI
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Digester Feeding

Good day Biogas practitioners and researchers. I am honored to be in such a wonderful community. Please, I would like to ask some questions regarding feeding of my digester:

1.) After I have started up my digester with animal dung, do I add food waste after a partuclar number of days, or i wait for it to start burning before I start adding food waste?

2.) How much food waste is to be added to a digester and at what rate (according to the size of the digester). I have a 120 liter digester so how much food waste do i add daily into such digester?

3.) Am I meant to dilute the food waste being added to the digester with water to 8 percent total solid before pouring it into the digester?

Thank you all as you help in providing answers to my question.

Nick Chase
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1) once you get a flame you

1) once you get a flame you start adding food waste
2) you could feed 1/20th of the size of the digester = 120 / 20 = 6 litre
3) actually you could dilute it much more, perhaps Janice could give us some details.

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RAROSUE AMARAIBI
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Feeding rate and water content.

Thank you Nick. I believe the feeding rate of 1/20th of digester size daily has the water content inclusive right? What I am asking is that do I have to mix the my food waste with water to get the 1/20th size, or I use 1/20th size of the food waste then add water to dilute it?

Nick Chase
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yes 1/20th of the digester

yes 1/20th of the digester size includes water. Everything is calculated down to the Hydrolic Retention Time (HRT). HRT in small scale digestors is usually between 20 to 30 days.

Size of Digester / HRT = feeding rate
120L / 20 days = 6L/day
120L / 30 days = 4L/day

And yes, this is including water. I can't give you an exact percentage of dry matter (solids) to water dilution ratio. This is another calculation and depends on what your are feeding. Rule of thumb: the better your digester is established the more solids can go in.

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