When the cows milk production falls off they are shipped to a nearby slaughterhouse. You have to admit it is very "efficient". Hundreds of acres devoted to making fake cheese. Just imagine the difference if the fake cheese were made from soy beans instead (like tofu). Policies not Politics ---- Daily Landscape
And, of course, you can lable "Farmhouse Cheddar", but not "Fake Cheddar" ;)
And don't forget the energy requirements don't end at slaughter. The assorted body parts are then processed, stored (in cold rooms, if you're lucky - for a long time if you're not) and distributed.
What would be hugely interesting would be the energy requirements needed to get a frozen lasagne onto someone's plate.
Re: biofuel - doesn't it depend on which sort? Ethanol is energy intensive, but I'd guess methane farming, while smelly and unpleasant, would be much less so. How much methane would the sewage from a large city produce, and what would the energy equivalent be?
As for gathering methane from city waste... you must have missed Nomad's smelly diary Nothing is 'mere'. — Richard P. Feynman
As for agriculture, certainly we have to distinguish between biodiesel (rapeseed/sunflower-seed oil to be used in diesel engines) and ethanol (alcohol to be used in petrol/gasoline engines) -- and then again between different crops used to produce ethanol, since there are considerable efficiency differences. (Sugar cane > sugar beet > maize/corn > wheat etc).
Personally, as far as Europe is concerned, i'm afraid of a scramble to obtain subsidies for ethanol operations based on dubious efficiency, on the part of agri-lobbies (sugar-beet and maize in particular). Ethanol is being touted by pundits as a miracle fix for oil worries. Which it ain't gonna be.