I know a little about this so ...
Biogas plants (production of electric through anaerobic digestion) takes about 20 years to become profitable, slightly less if you use parasitic heat takeoff.
Wind energy is very finely balanced, the turbines use oil based products anyway, it really depends where you get your materials from, if you buy your steel from the East, it will be cheaper, but environmentally far more expensive. The profit margins are minimal here, and it really depends on who you talk to and where you source your materials.
There are a number of other technologies, all of which require subsidies (read: not commercially viable yet), but all become profitable over long term use, one of the more promising is combined heat and power which is a mixture of technologies to use every bit of power a boiler produces. The basic problem here is that the calorific value of oil is very high, and there are no technologies we have that compare.
Another main problem is that most statistics do not specify the different types of cost, as an example, there is the economic cost, the environmental cost, the human impact cost, longitivity cost. For instance, solar cells could be used in warm countries effectively, energy for nothing you may say, but although people should factor the cost of getting rid of them at end of life, they don't as this is very high, (most solar cells contain large amounts of heavy metals etc but in small quantities around the board: this is very costly to remove). Generally putting the environmental cost into the equations means fossil fuel technologies' costs rise massively, and visa versa for green technologies. We pay the economic cost immediately, the environmental cost later. Good examples of environmental costs are the cost to clean `brown field' sites of heavy metals, this is one reason why builders prefer to build on `green field' sites, and parts of Southampton are still expanding into the countryside when there are parts of St. Marys (in Southampton) that could be redeveloped after being bombed in WWII 60 years ago!!!
Greg