Can you store fart gas and use it?

No. It is methane, which causes global warming.

You could use the methane to produce electricity, however it is quite impractical and inefficient to catch your farts for large scale use. They do use the methane from cow excrements to make electricity though.
For human farts, I think the only sensible use is to fill it into stink bombs and play pranks.

Not exactly, but methane from cow manure and landfills is used to produce electricity.

A couple of examples:

Albert Straus has figured out a way to run his dairy farm, organic creamery and electric car from the manure generated by his herd of 270 cows.

Methane recovery facility has been operational since 1993 with an annual production of energy equivalent to 112,000 barrels of oil.

I store mine.

Every time I read something that makes me roll my eyes I force out a fart. I try to save them up for when I know I’m going to be on Fluther for a good stretch.

I could not resist the urge, so here’s my serious answer. I looked around and found numbers like the average person producing half a liter of methane per day. Some places have that at zero so it clearly depends upon your diet.
Let’s give it the benefit of the doubt and say it is 90% methane with a mix of ethane and propane with an effective net molecular weight of 22.5.
That means you would produce 0.5 grams of the hydrocarbon fuel mix per day.
Methane has an energy density of 55MJ/kg, so that would produce 27,000 joules per day.
About the same amount of energy stored in 1 cc of ethanol.

Now what can it do? 27000 joules = 0.0075kWh. Electricity costs $0.15 cents per kWh so if you were to somehow turn all that gas into electricity at 100% efficiency, it would be equivalent to 0.0075kWr x $0.15/kWh = 0.1 cent per day.
So figure all your flatulence can do the same amount of work as 0.1 cents worth of electricity per day. Not much.

Don’t even get me started about where and how you would store it. Don’t… Oops! Too late.
With 500ml of storage, guys can present an impressive package and women can emulate JLo.
Shake your money maker.

Storing the methane produced by a fart could theroetically becaptured and stored in a cylander, and then burned to produce electricity.
You will need to have a lot of gas to make it worth while.
Give the product a name with a cool electic sounding name. I suggest: “Watt Di-ed”

Methane is fairly ordorless, which is why the gas company adds smell so people can detect it. The “rotten eggs” smell (I’m being kind here) of flatulence comes mainly from hydrogen sulfide (H2S) gas, which people are sensitive to, along with plenty of other odoriferous organic gas molecules produced by bacteria in your intestines.

You’d need a mass spectrometer to fully sort it out. This has been done. The wikipedia article on flatulence names skatole, indole, methanethiol, and dimethyl sulfide as additional culprits in the unpleasant smell.

H2S is commercially available in cylinders of compressed gas, a fact I just discovered on the internet.

Storing the methane produced by a fart could theroetically becaptured and stored in a cylander

Challenge accepted!

…In a bid to understand the impact of the wind produced by cows on global warming, scientists collected gas from their stomachs in plastic tanks attached to their backs…

Poor cows. The indignity!

You can store methane and use it as a power source. There is a house in Dunedin, NZ where this was done. Lenach Castle has a methane-gas generation plant in the garden.

“Former PM Seddon heralded Larnach as “the man with a mind which was a master
mind” and many of Larnach’s innovations, like his scheme for lighting the castle, were ahead
of their time. The chandeliers throughout the house were lit using methane gas collected
from an outhouse built in the shape of a Maltese Cross and euphemistically called “The
Gas Generator”. Inside the outhouse were long drops and a lad was employed solely to pump the trapped gas up to the castle.” (MacFarlane)

There isn’t a lot written about it that I can find but the owner of the house does seem to have been well ahead of his time.