Biogas production from Spent Grains

[ZeDrunkenMaster]

Hi hi.

So, I have built a biogas digester for my home cooking needs, which works great and I have always wondered about the requirements for a system to fuel my burners.
Spent grain, hops, trub all straight into the digester for free fuel!

I have a 500L brewhouse with 1 35kw and 2 26kw burners in a three vessel system.

My biodigester capacity will be 26L/min with adequate storage so as not to run out (would probably run a hybrid system in any event).

Does anyone have info on L/min requirements in a brewery/amount of gas used per brew? Need to size my digester adequately.

Will carry out my own research also in case this information is not yet out there.

Many thanks!
Brew on!
JB

[rdcpro]

Hi hi.

So, I have built a biogas digester for my home cooking needs, which works great and I have always wondered about the requirements for a system to fuel my burners.
Spent grain, hops, trub all straight into the digester for free fuel!

I have a 500L brewhouse with 1 35kw and 2 26kw burners in a three vessel system.

My biodigester capacity will be 26L/min with adequate storage so as not to run out (would probably run a hybrid system in any event).

Does anyone have info on L/min requirements in a brewery/amount of gas used per brew? Need to size my digester adequately.

Will carry out my own research also in case this information is not yet out there.

Many thanks!
Brew on!
JB

I can't answer your question on how much gas it will take, but I have experience with large scale biogas/cogeneration systems, and the problem that needs to be solved is the varying energy content of the digester gas. We used a Fischer-Porter controller that measured the energy content of the digester gas, and adjusted a proportioning valve to mix in natural gas of a known BTU content in order to regulate the energy content. It was a very complicated system, but worthwhile on the scale we were using. The biogas was mostly used to run large Waukesha engines with regenerative blowers which was used to aerate the activated sludge tanks after the digester. There was also an electrical generator that was sometimes run. A burner may not be as sensitive to varying energy content, though. We were required to do this, however, to meet air quality regulations.

Regards,
Mike Sharp

[ZeDrunkenMaster]

I can't answer your question on how much gas it will take, but I have experience with large scale biogas/cogeneration systems, and the problem that needs to be solved is the varying energy content of the digester gas. We used a Fischer-Porter controller that measured the energy content of the digester gas, and adjusted a proportioning valve to mix in natural gas of a known BTU content in order to regulate the energy content. It was a very complicated system, but worthwhile on the scale we were using. The biogas was mostly used to run large Waukesha engines with regenerative blowers which was used to aerate the activated sludge tanks after the digester. There was also an electrical generator that was sometimes run. A burner may not be as sensitive to varying energy content, though. We were required to do this, however, to meet air quality regulations.

Regards,
Mike Sharp

Hi Mike. Thanks very much for your input.

I have seen New Belgium using the very same Waukesha/co gen engines (from the images I have seen) in their biogas set up though I'm not sure what the gas they create powers? Possibly boilers and generators.

I had thought about the varying energy content also but as you say, had not anticipated its impact on simple burners vs complex boiler/electrical generator systems.

I think the question I need to answer is; how much gas I will need vs how much gas I can reasonably expect to produce vs how energetic the gas I produce will be!?

It may be a lost cause but I'd like to at least entertain the idea that it is feasible!

You have given me good fuel for thought so thank you again.

Cheers.
JB