Anaerobic digesters have been used for wastewater sludge digestion for decades. Much of the methane produced is used to heat the digestion process, particularly in cold climates like Vermont.
I suspect the 200 cfm is the maximum biogas output rating, not the nominal output. It would be interesting to know what percentage of the biogas is methane, and how they dispose of the waste sludge generated by the digester.
You'd have to brew a lot to make a home model feasible.