I'd go for it. As you're probably aware, the methane thingie uses anaerobic fermentation to produce a combustible gas, in the process destroying any nasty viruses or bacteria, just like a septic tank.

Aerobic composting heats up and lets off CO2 not CH4.

Anaerobic digestion, and septic tanks, do not destroy any disease pathogens, bacteria or virus, although as the effluent form those tanks is filtered they might be locked into the soil. But generally time, how long it takes that effluent to move back into out drinking water is a bigger factor.

That manure could be a good addition to any soil as long as it is accompanied by adequate levels of vegetative waste, 3 parts vegetative waste to 1 part manure.