Energy prices and energy sales possibilities seem to be the most important preconditions for the viability of agricultural biogas plants. Some countries provide opportunities for electricity sale at prices of approximately US$ 0.10-0.15 per kWh. This price level provides sufficient incentive for farmers and other investors to become interested. In other countries, where much lower prices are offered, agricultural biogas plants do not expand. General preconditions for farming probably comprise the second most important factor. Reduced odours and improved fertiliser characteristics are important benefits of the digestion process. The process can also play a key role for co-operatives dealing with organic fertiliser declaration and redistribution. A relatively wide range of investment and operating costs are experienced for similar plants. Most likely this reflects that market forces are relatively weak. Considerable reductions in costs may be achieved from efforts within the whole range of technical issues from slurry handling and onwards, with the issue of electricity production being one of particular importance. Anaerobic digestion may imply environmental benefits with regard to waste treatment, pollution reduction, energy production, and improvements in agricultural practices. Agricultural and environmental government agencies are in need of further information on this. Questions concerning environmental benefits of various anaerobic digestion solutions need to be answered in an increasingly more accurate manner.