Digester Heating

To achieve the optimum biogas yield, the anaerobic digestion needs constant environmental conditions, preferably close to the process optimum. The digester temperature is of prime importance. In temperate areas, a heating system and an insulation of the digester is necessary. Hence, the needed temperature for digestion can be reached and a loss of energy by transmission is compensated.

There are a number of different ways to get the required amount of thermal energy into the substrate.

• direct heating in the form of steam or hot water, and
• indirect heating via heat exchanger, whereby the heating medium, usually hot water, imparts heat while not mixing with the substrate

https://energypedia.info/wiki/Digester_Heating

Thanks Mister Gaurav.

But, as said, it's a home digester not industrial ones. It's made of flexible strong PVC.

Problems:

The farmers can't buy expensive systems.

And the rural zone has no electricity.

For all these reasons, I asked help to this website, full of experts.

So we have to find a solution in this hard situation.

Thanks in advance.

Best greetings.

You can add hot water with feed.

Dear, you can take advantage of Hot water bath OR Aquarium heater/rod that can submersed into the liquid.

Good morning Vijay and thanks so much for kind support.

I know this solution, but do you know big heater enough powerful to warm the digester up to (at least) at 25°C? Now the temperature is 10-12°C and it doesn't produce biogas. The digester is very big (4.5 m3) and I don't know a so big heater for the liquid inside. Thanks in advance for any support. Best regards, Caterina

Hi Caterina Buluggiu ,

Yes, a simple greenhouse and insulation. See research by @Jaime Martí-Herrero here on researchgate.

One observation (O), two questions (Q), and two ideas (I):

O: If the design and operation keep the temperature and the feedstock changes gradual, the biology will adapt. As the contents move into psychrophilic range, biogas production slows down.

Q:

1.) With a bag-type digester, how will you deal with solids filling up the bags? Remove them upstream, clean them out (how often? in what way?), and/or cut the bag and remove/discard it all?

2.) Have seen yet how this works, on your own projects? Or someone else's project?

I:

1.) Install 50-100 days of minimally weatherized or minimally heated bags and 20-30 days of better-weatherized bags.

2.) Install a small number of vacuum-tube solar collectors and a PV panel. This will get you heat in the winter when you need it. In spring, it's a perfect match as the sun is strong in March, while the ground is still cold.