if only biogas could be used as a fuel..., page-4

Yes that is the sweetest part. Because the digestion is sealed it is oxygen free (anaerobic) so instead of losing the nitrogen to the air as ammonia it remains in the slurry as a really nitrogen rich fertilizer. And because it has already been munched up and well distributed in the water it pours easily enough and is simple to apply. Many piggeries are run, generating power from methane, but they usually use the gas to run a motor.