It should be noted that there can be some dangers associated with digesters. Hydrogen Sulfide levels can be high and even deadly depending on the feedstock. This will vary from digester to digester, but can be managed if you are aware. Also fire and explosions are rare but possible.

They can be complicated to operate. It takes some skill. But they are useful and millions were successfully employed across China in the 70's at small farms.

Finally a solid 'digestate' is often wasted from larger digesters. Smaller ones might be scooped out from time to time. If human waste is introduced into the digester, the digestate it becomes a different class of waste material. At least in many jurisdictions.