[Digestion] Test Message

Sun Nov 7 11:14:27 CST 2021

Interesting conclusions. There are now many peer reviewed papers on biochar addition to digesters. Result vary according to biochar feedstock, processing conditions, and likely with digester feed such as food waste or biosolids. Positive results in solids removal, COD removal, methane production and ammonia nitrogen reduction have stimulated further research.  

Tom

From: Digestion <digestion-bounces at lists.bioenergylists.org> On Behalf Of Anand Karve
Sent: Sunday, November 07, 2021 8:31 AM
To: For Discussion of Anaerobic Digestion <digestion at lists.bioenergylists.org>
Subject: Re: [Digestion] Test Message

We had filled the biochar into a nylon net-bag and placed the bag into the digester. In this way, the biochar remained in the digester as long as we wanted it to be there. The bag was removed from the digester only after we found that the biochar was no longer effective. We do not recommend application of biochar to a biogas digester. The experiment was conducted only to find out how the biochar affected the performance of a biogas plant. Now that I know the role played by biochar as a donor of minerals, we are using ordinary field soil instead of biochar. The universal presence of green plants in nature shows that all soils in the world have all the minerals that living beings need.

Yours

A.D.Karve

On Sun 7 Nov, 2021, 1:55 PM , <tmiles at trmiles.com <mailto:tmiles at trmiles.com> > wrote:

AD, 

It is great to hear from you. Many thanks for your observations and experience with biochar. The digesters that we know of that are adding biochar to food waste find that there are a number of benefits as you have experienced. They feed the biochar to the digester continuously along with the food waste and remove it with the digestate. They probably benefit from the minerals as well as pH buffering. As far as I know the biochar does not accumulate in the digester. What we have seen so far are results from  experiments at the lab scale and reports from some industrial scale use. We haven’t heard of biochar being used on the household scale. I wonder if others on the list have added biochar to digesters. 

Kind regards, 

Tom  

From: Digestion <digestion-bounces at lists.bioenergylists.org <mailto:digestion-bounces at lists.bioenergylists.org> > On Behalf Of Anand Karve
Sent: Saturday, November 06, 2021 10:33 PM
To: For Discussion of Anaerobic Digestion <digestion at lists.bioenergylists.org <mailto:digestion at lists.bioenergylists.org> >
Subject: Re: [Digestion] Test Message

Glad to hear from you and also glad to know that the list is still surviving. I am still working on food waste and kitchen waste as feedstock. One of the drawbacks of this feedstock was that one could load the digester with only a small quantity of feedstock at a time. But with our new design, we have overcome this problem. Now we load all the feedstock into a predigester. Because of overloading, the pH of the material in the predigester becomes acidic, but the  new design is such, that the digester draws in only so much of the acid, as can be converted by it into biogas.

Adding bichar certainly works, but only temporarily. The digester filled with biochar produced three times as much biogas as was possible without the biochar, but only for three months,. After 3 months we had to open the digester and load it again with fresh biochar. This indicated that food waste does not have enough minerals and that the ash in the biochar served the bacteria as a source of minerals. One can as well add chemical fertilizers to the digester to achieve the same results.

Yours

A.D.Karve

On Sun 7 Nov, 2021, 3:31 AM , <tmiles at trmiles.com <mailto:tmiles at trmiles.com> > wrote:

Thanks! A lot has happened in anaerobic digestion since the list was last active last Spring. 

1.	RNG. While we only have a small number of commercial digesters in the US compared with Europe there is a lot of excitement about Renewable Natural Gas, especially from the American Biogas Council. They report that there are 161 digesters that are now selling RNG and that there is a potential for something like 2000. The contracts for RNG appear attractive but it is not yet clear what the net benefit is to the owner after complex transaction fees are subtracted.  https://americanbiogascouncil.org/

2.	Food wastes are another emerging feedstock for AD in the US, almost as a pre-treatment for composting the digestate. 

3.	Research has demonstrated the value of adding biochar to AD feedstock with a variety of benefits but we don’t see commercial use of biochar yet in AD either as a digester additive or as an additive to digestate prior to composting.   

Tom     

From: Bruno M. <brunom1 at telenet.be <mailto:brunom1 at telenet.be> > 
Sent: Saturday, November 06, 2021 2:31 PM
To: For Discussion of Anaerobic Digestion <digestion at lists.bioenergylists.org <mailto:digestion at lists.bioenergylists.org> >; tmiles at trmiles.com <mailto:tmiles at trmiles.com> 
Subject: Re: [Digestion] Test Message

yep, works perfect Tom.

================================

Op 6-11-2021 om 21:02 schreef tmiles at trmiles.com <mailto:tmiles at trmiles.com> :

This is a test to see if the list is still available

Tom Miles

Digestion list Owner

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