[Digestion] Small scale digester heating and more

[PETER ALLISON]

Kyle, so many questions.
 
I will attempt to answer all your enqueries in order as follows;
 
Peter, how much power did your system require for pumping? 
Minimal,. the 500W pump ran for one minute in fifteen for the period when heat was available. The pump was more powerful than required, but it was one I had available and was valved to deliver at a reduced rate so that stored heat would be introduced onto the external digester wall and displace thermally depleted water.  Worked very well.

Is there a way to do away with the pump?       
No, because the heat exchanger was a coil configured irrigation tube.You could avoid the pump, but the heat exchange system would need a complete redesign.

How much did a cloudy day affect the heating system?    
Somewhat, temperature would drop by 1 degree overnight or cloudy day, a warm day would add 2 degrees to the digestion.

How much power was required to run your control system (if any)? 
Minimal. 750W for one minute per hour was sufficient to disturb stratification, prevent settling and maintain a homogenious slurry. Controlling was done by an electronic timer.

It is good to hear that your mesophilic digester was able to produce better fertilizer than the ambient temperature digester.       
I don't think the retention time determines fertilizer quality. As long as the process is complete the values of the spent digestate should remain the same. Higher temperatures increase reactivity and as a result retention times are reduced. You still end up with the same finished humic, fulvic and colloidal substances.

I have seen a website for a company in Australia called biobowser. Is that the same company?     
Yes

It looks like a beautiful technology all packaged into one easy (?) to install modular unit.     
Thank you, it was designed to be simple to install, operate and service as well as being globally transportable to any location serviced by container-carrying trucks..

Is there a reason why their smallest unit is for 100kg per day?       
To cater for very small volumes of waste, I guess. It does not require exactly 100Kg, it could be a bit less, it could be a bit more.

Could their system be scaled down?      
Sure it could, just as it has been scaled up but why bother. The 1000L prototype required about 25-40L of waste per day for continuous feeding. How small would you want to go, anyway?. If you are chasing gas, you would need at least one cubic meter per day of methane to make the exercise worthwhile. One cubic meter would be sufficient to boil water for about an hour. The 1000L bio-reactor produced 2 cubic meters of better than 90% methane per day when peaking.

Best Regards,
Peter.

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