Cow co-firing

Cows burp out a fair amount of methane [1], which in most cases escapes to the atmosphere where it acts as a potent greenhouse gas.
It has often been suggested [2] that this methane could be salvaged, however, previous methods involved strapping collectors to the cows themselves. These don't seem to be widely practiced presumably due to implementional difficulties.
Due to the changing nature of farming, many cows now spend most of their lives indoors, in huge groups which rarely if ever go outside. There are literally shed-loads of cows. This obviously opens up an opportunity to acquire the bulk of the methane, provided it can be used immediately and at low concentration.

I therefore propose that a (fossil fuel, or biomass) powerstation could use this methane by the simple expedient of drawing its air through the cowshed.[3]

The only potential drawback to this method that I can see is that the input air would have slightly reduced oxygen content, and potentially increased humidity - both of which may reduce efficiency. Hopefully the latter could be mitigated by careful design, and together these effects would be smaller than the overall gain from the increased fuel supply.

[1] According to one report, on average 250 litres of methane per cow per day. This represents 11.2 moles, which would provide almost a megajoule of heat (HHV)on combustion.

[2] See: other ideas in this category.

[3] This could be complemented by methane from anaerobic digestion of manure, which has the advantage that it is at higher concentration and can therefore more easily be stored to help with peak load.