What's dangerous about the digesters? What are the storage problems, and do those problems involve the methane or something else? These are both non-antagonistic technical questions, especially because, on its surface, this looks like a promising technology for turning a definite pollutant into economical energy.
I guess if you kept your holding/regulating system far away from the barns (like 1000'), that would work better.
I guess if we'd spent a few million on technology we'd have come out better. We spent about $2,500 and used scrap/farm fabricated materials. We could have used it for our house needs from May thru September. Once it dropped to the teens and below it was not feasible. Too much energy spent to heat the slurry.
And FWIW, our insurance company would not continue our policy with an on-site methane digester. We did have some really impressive fireballs.