Biogas technology is not a universally accepted technology such as the transistor radio. A biogas plant has to fit into existing farming-, production- or waste disposal systems. Attempts to make the system fit to the biogas plant will result in expensive and frustrating failures.
Biogas technology has many competitors. Energy can be produced by fuelwood plantations (with other positive side-effects), by solar systems, micro-hydro-power and other renewable energy technologies. Producing high quality fertilizer can be done in other, cheaper ways such as composting which are even closer to traditional techniques.
What makes biogas an attractive option is the fact that this technology can provide solutions to a variety of problems simultaneously. That is, if this variety of problems exists.