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Science: Energy: Wind
Cow Windmill   (+3, -7)  [vote for, against]
Power from cow farts without creating carbon dioxide

Cows generate up to 1000 liters a day of flatulent gases. This invention would see that some of this 'free energy' is put to use.

A small propeller with turbine is attached to an arm and harness sticking out the backside of cow. The propeller is positioned 'downwind', but not so close as to be in danger of pooification.

The turbine is connected to a rechargeable battery pack slung over the back of the cow. When the cow comes in for milking, the battery pack is swapped out with another, and the charged battery is plugged in to power various items on the farm.
-- Cedar Park, Jul 27 2008

Cow Destroys The Planet http://www.dailymai...climate-change.html
[Amos Kito, Jul 27 2008]

Power Cows http://jeq.scijourn...t/figsonly/32/1/269
[2 fries shy of a happy meal, Jul 27 2008]

The rest of the cow fart related ideas. http://www.halfbake...energy_3a_20Methane
Hey, if a joke is good once, it'll be ten times as good if you repeat it ten times, right? [jutta, Jul 27 2008]

Mooood lighting.
-- 2 fries shy of a happy meal, Jul 27 2008

You've put the turbine on the wrong end. [Link]
-- Amos Kito, Jul 27 2008

[-] you intend to waste the gas to atmosphere after turning the propeller. if the gas has heat value, collect it using some automatic vacuum system & derive useful energy by burning it.
-- vedarshi, Jul 27 2008

The mixture is not adequately rich to allow any real use.
-- WcW, Jul 27 2008

But it can be. [link]

It's nice to see that someone is actualy trying to harness the energy.
-- 2 fries shy of a happy meal, Jul 27 2008

Gas fractionating is not as simple as it seems.
-- WcW, Jul 27 2008

Could not find a direct source for the concentration of methane in a cow fart. Here's what I did.

various sources:
cow farts 10kg methane a year
cow farts 800 liters volume per day

That's 292,000 liters per year.
Density of methane is 6.67*10^-4 g/cm^3. There is 1.5*10^7 cm^3, or 15,000 liters of methane in a year of farts.

15,000/292,000 = 5.13% methane in the farts.

Wikipedia says the gas is flammable only between 5 and 15% in air.

These calculations suggest that you are wrong, [WcW]. No fractionation is required as the gas will usually be combustible in it's native concentration.
-- daseva, Jul 27 2008

The vast majority comes out the mouth.
-- Texticle, Jul 27 2008

Yes but still worthless as a fuel as it would be impossibly bulky to store at that concentration. Even more important if used to power a generator that is only 60kWh per YEAR (at a comical assumed efficiency). We could debate the merits of fuel concentration (less is bad) but the simple fact that a few pounds worth of dried dung yields the same quantity of energy should help make clear the basic point. The issue is not that farting yields a vast untapped resource but that it yields an additional green house gas. Also that cows are a huge waste of the food that they consume thus that it should be otherwise worthless (unless you like turning nice food into very flammable farts and dung).
-- WcW, Jul 27 2008

//without creating hydrocarbons//

WTF? The burps and farts are mainly methane. Methane is, practically, a hydrocarbon.

Maybe that's meant to say "without creating carbon dioxide", by avoiding the burning of said hydrocarbon, in an effort to reduce greenhouse gasses. Well, methane is a greenhouse gas, and probably should be burnt into CO2 before it dissipates.

When I read this, it seems that the idea is to just use fart power to spin a windmill, just by blowing. Folks seen to be reading in an assumption that it burns the methane, and arguing that. I see only that it uses the force of a fart to power a turbine, much as humans use the force of a fart to lift blankets. Combustion and methane flammability are nowhere in it. The subtitle maybe should be "without burning hydrocarbons".

If this is the non-combusting Le Pétomane approach, I suggest that the rig should be converted to capture the power of the cow's breathing. A turbine hung over the nostrils should get a lot more breeze.
-- baconbrain, Jul 27 2008

No, we were working off a previous anno: //if the gas has heat value, collect it... & derive useful energy//

what about dinosaurs?
-- daseva, Jul 27 2008

[WcW] //Even more important if used to power a generator that is only 60kWh per YEAR (at a comical assumed efficiency)//

Yes, it is comical if you have read too much between the lines. Simply consider a burner system (may be similar to domestic one) to burn gas for heating purpose i.e. a fully baked PNG (Piped Natural Gas) system.
-- vedarshi, Jul 28 2008

I doubt that a system mounted to a cow would achieve an efficiency btu/kWh comparable to a generating plant. 60kWh is far less than the cow could be made to produce turning a mill for a single day.
-- WcW, Jul 28 2008

Well yeaaah. But they fart and burp without training.
-- 2 fries shy of a happy meal, Jul 28 2008

I like the battery swap out - how about a jersey of thermocouple tiles . Keep the cow warm and dry and charge batteries . How much heat does a cow put out ?
-- wjt, Jul 28 2008

Yes , a Peltier matrix coat for cows .
-- wjt, Jul 29 2008

I think you'd have better luck putting the herd all in some kind of air-tight-ish barn where the ventilation is scrubbed for the hydrocarbons (could also use the hot gas as a heating source), which are then refined and then used as a fuel source elsewhere. moooo.
-- gomer, Jul 29 2008

You'd probably generate more energy by either strapping a windmill to the back of the cow, or harnessing the power of her tail.
-- Noexit, Jul 29 2008

I remember a movie about hog emissions where they were kept in a thunderdome.
-- baconbrain, Jul 29 2008

random, halfbakery